1

NORTHEAST POTATO TECHNOLOGY FORUM - 2016

INTRODUCTION

The Northeast Potato Technology Forum is an annual event which brings together potato specialists from northeastern North America to discuss potato research and promote collaboration and information exchange. The twenty-third annual Northeast Potato Technology Forum was held March 16-17, 2016 at the Crowne Plaza Lord Beaverbrook Hotel in Fredericton, New Brunswick.

A total of 28 oral scientific presentations were made as part of five sessions grouped by subject matter. Sessions dealing with insects and viruses, potato pathology, breeding, genetics and nutrition and cropping systems, propagation and storage management were organized. Presentations were extremely diverse and represent a cross-section of potato research in the region.

Many thanks to the session chairs, presenters and all who participated in Forum 2016. We would particularly like to thank Syngenta for sponsoring the reception and McCain Foods for publishing this book of abstracts. We would also like to thank all of the sponsors (see sponsor page) for their support. This booklet contains abstracts of the 28 oral presentations made at the Forum. The research work represented by these papers forms an important part of the ongoing development of the potato industry in the northeast region.

Local Chair: Brian Beaton

Local Organizing Committee: Brian Beaton, Rick Peters, Loretta Mikitzel and David Thompson

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Table of Contents

Page

Introduction 1

Scientific Program 5

Abstracts

Session A: 8

Herbicides for the Control of Volunteer Potato. Graham, G.L.*

9

Using gene expression-based diagnostics to assess potato crop

N status: Recent progress B.J. Zebarth* and H. H. Tai

10

Can reduced N rates supplemented with foliar urea application

increase nitrogen use efficiency and potato yield and quality? Nyiraneza Judith* and Dave Burton

11

Cumulative and Residual Effects of Potato Cropping System

Management Strategies on Crop and Soil Health Parameters Robert P. Larkin

13

Spatial variation in soil bacterial and fungal communities in a

commercial potato field Claudia Goyer*, Sara Neupane, Bernie J. Zebarth, Sheng Li, and Sean Whitney

17

Session B: 20

Can we find the “right” compost for New Brunswick Potato

Production? Carolyn Wilson*, Bernie Zebarth, David Burton, Claudia Goyer

21

The Effect of Compost on Russet Burbank Yield and Quality Gilles A. Moreau*, Bernie Zebarth

22

Effect of Compost on Small Grain Grown in Rotation with Potatoes Daniel Savoie * and Gilles A. Moreau

24

Effect of Compost on Potato Soil Physical and Biological Properties Pat Toner *, Gilles A. Moreau, Bernie Zebarth

25

Spatial and temporal variation of selected soil fertility parameters in

Prince Edward Island Judith Nyiraneza*, Sherry Fillmore, Barry Thompson, Kyra Stiles, John MacLeod, and Yefang Jiang

26

Evaluation of 4R Fertilizer Strategies on the Performance of PEI

Potatoes Steve Watts

27

Session C: 28

Quantifying differential spread of three PVY strains in the field:

Potential explanations for the recent increased prominence of

PVYNTN

Tyler MacKenzie*, Jacques Lavoie, Janet McLaughlin, Mathuresh Singh

29

3

The Use of Mineral Oil for the Management of Potato Virus Y:

Deciphering the Mode of Action. Sébastien Boquel*, Jianhua Zhang, Marie-Andrée Giguère, Catherine Clark, Xianzhou Nie

31

Identification and characterization of an Alfalfa mosaic virus isolate

in potatoes exhibiting internal necrosis Xianzhou Nie*, David De Koeyer , Zengenni Liang, Virginia Dickison, Mathuresh Singh, Gary Hawkins

33

The Use of Cryotherapy for Elimination of Potato Virus S (PVS) from

Tissue Cultured Potato Plants of Potato Seedling PR07-11-1 Robert Coffin*, Andrew McCartney, Xiuying He, Mathuresh Singh, Angela Gallagher and Joyce Coffin

34

Utilization of new sources of dual resistance to PVY and

late blight in potato breeding. Benoît Bizimungu*, Agnes Murphy, Ramona Thieme and Thomas Thieme

39

Session D: 40

Study of Verticillium pathogens in potato production systems in the

Maritimes Gefu Wang-Pruski*, Tudor Borza, Rick Peters, Xingxi Gao, Yahui Liu, Kim Best, Kris Pruski, Brian Beaton, Zenaida Ganga and Dorothy Gregory

41

Alternative management strategies to control fungicide‐resistant

Phytophthora erythroseptica populations in Canada. RD Peters*, Crane, B, LM Kawchuk, KI Al-Mughrabi, A MacPhail, KA Drake, D Gregory, and M. Trenholm

42

Bacterial antagonists as a biological solution for control of potato

late blight. Patrice Audy*,Nicholas Foran, Susan M. Boyetchko and Valerie Grave

43

The Use of Bacillus bacteria Applied In-Furrow to Reduce Common

Scab on Potatoes Robert Coffin*, Joyce Coffin, Steve Watts, Claudia Goyer and Catherine Clark

44

Management options to reduce wireworm damage in potatoes Christine Noronha*, Natasha Boyle and David Carragher

49

Metabolomics of Colorado potato beetle resistance in

S. oplocense X S. tuberosum hybrids Helen H. Tai*, David de Koeyer, Kraig Worrall, Yvan Pelletier and Larry Calhoun

50

Session E: 51

Reduced Steroidal Glycoalkaloid Levels Affects Solanum tuberosum

resistance against Pests and Diseases Jamuna Risal Paudel*, Charlotte Davidson, Leslie Campbel, Cathy Clark, Lana Nolan, Jun Song, Agnes Murphy, Maxim Itkin, Asaph Aharoni and Helen H. Tai

52

4

The Effects of Low Levels of CIPC on Seed Potato Performance John Walsh

53

Uncovering associations between the genomic segments and

selection parameters with disease resistance and agronomic and

quality traits in cultivated potato Jiazheng Yuan*, Agnes Murphy, David De Koeyer, Umesh Rosyara, Martin Lague, and Benoit Bizimungu

55

Identification of chromosomal locations in potatoes associated with

tuberization traits affected by photoperiod using SNP markers. Maria Caraza*, David De Koeyer, Elisa Mihovilovich, Merideth Bonierbale, and Gefu Wang-Pruski

57

Biological predictors for tuber sweetening during long term cold

storage. Jonathan Neilson*, Martin Lagüe, Susan Thompson, Frédérique Aurousseau, Agnes Murphy, Benoit Bizimungu, Virginie Deveaux, Yves Begue, Jeanne Jacobs and Helen H. Tai

58

Sweet potato clonal differences in organic trial performance, dry

matter content, starch content, and starch granule characteristics in

New Brunswick Xiu-Qing Li *, Suyan Niu, Ruimin Tang, Fanrui Meng, Guoqiang Fan, Qing Yang, Loretta Mikitzel, and Muhammad Haroon

59

5

Northeast Potato Technology Forum 2016 - Scientific Program March 16 – 17, 2016

Crowne Plaza Lord Beaverbrook Hotel Fredericton, NB Canada

Wednesday, March 16th

1:15-1:30 Welcome: Brian Beaton, PEI Department of Agriculture and Fisheries

Moderator: Loretta Mikitzel, NBDAAF, Wickow, NB

1:30 Herbicides for the control of volunteer potato. Gavin Graham*

1:45 Using gene expression-based diagnostics to assess potato crop N status: Recent progress. Bernie J. Zebarth* and Helen H. Tai

2:00 Can reduced N rates supplemented with foliar urea application increase nitrogen use efficiency and potato yield and quality? Judith Nyiraneza* and Dave Burton

2:15 Cumulative and residual effects of potato cropping system management strategies on crop and soil health parameters. Robert Larkin*

2:30 Spatial variation in soil bacterial and fungal communities in a commercial potato field. Claudia Goyer*, Sara Neupane, Bernie J. Zebarth, Sheng Li and Sean Whitney

2:45 BREAK

Moderator: Brian Beaton, PEIDAF, Charlottetown, PE

3:30 Can we find the "right" compost for New Brunswick potato production? Carolyn Wilson*, Bernie Zebarth, David Burton, and Claudia Goyer

3:45 The effect of compost on Russet Burbank yield and quality. Gilles Moreau* and Bernie Zebarth

4:00 Effect of compost on small grain grown in rotation with potatoes. Daniel Savoie* and Gilles Moreau

4:15 Effect of compost on potato soil physical and biological properties. Pat Toner*, Gilles Moreau, and Bernie Zebarth

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4:30 Spatial and temporal variation of selected soil fertility parameters in Prince Edward Island. Judith Nyiraneza*, Sherry Fillmore, Barry Thompson, Kyra Stiles, John MacLeod, and Yefang Jiang

4:45 Evaluation of 4R fertilizer strategies on potato yield and quality in Prince Edward Island. Steve Watts*

5:30 HOSPITALITY SUITE (Suite 118) courtesy of Syngenta

Thursday, March 17, 2016

7:00 – 8:00 Breakfast

Moderator: Christine Noronha, AAFC-CRDC, Charlottetown, PE

8:30 Quantifying differential spread of three PVY strains in the field: Potential explanations for the recent increased prominence of PVY-NTN.

Tyler MacKenzie*, Jacques Lavois, Janet McLaughlin, and Mathuresh Singh

8:45 The use of mineral oil for the management of Potato Virus Y: Deciphering the mode of action. Sébastien Boquel*, Jianhua Zhang, Marie-Andrée Giguère, Catherine Clark, and Xianzhou Nie

9:00 Identification and characterization of an Alfalfa mosaic virus isolate in potatoes exhibiting internal necrosis. Xianzhou Nie*, *, David De Koeyer, Zengenni Liang, Virginia Dickison, Mathuresh Singh, and Gary Hawkins

9:15 The use of cryotherapy for removal of potato virus S (PVS) from tissue cultured plants

Robert Coffin* ,Andrew McCartney , Xiuying He, Mathuresh Singh, Angela Gallagher and Joyce Coffin

9:30 Utilization of new sources of dual resistance to PVY and late blight in potato breeding. Benoît Bizimungu*, Agnes Murphy, Ramona Thieme, and Thomas Thieme

9:45 BREAK

Moderator: Robert Larkin, USDA-ARS, Orono, ME

10:30 Study of Verticillium pathogens in potato production systems in the Maritimes Gefu Wang-Pruski*, Tudor Borza, Rick Peters, Xingxi Gao, Yahui Liu, Kim Best,

Kris Pruski, Brian Beaton, Zenaida Ganga and Dorothy Gregory

10:45 Alternative management strategies to control fungicide-resistant Phytophthora erythroseptica populations in Canada.

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Bennett Crane, Rick Peters*, Larry Kawchuk, Khalil Al-Mughrabi, Anne MacPhail, Kathryn Drake, Dorothy Gregory, and Michelle Trenholm

11:00 Bacterial antagonists as a biological solution for control of potato late blight. Nicholas Foran, Patrice Audy*, Susan M. Boyetchko and Valerie Gravel

11:15 The use of Bacillus bacteria applied in-furrow to reduce common scab on potatoes. Robert Coffin*, Joyce Coffin, Steve Watts, Claudia Goyer, and Catherine Clark

11:30 Management options to reduce wireworm damage in potatoes. Christine Noronha*, Natasha Boyle, and David Carragher

11:45 Metabolomics of Colorado potato beetle resistance in S. oplocense X S. tuberosum hybrids. Helen Tai*, *, David de Koeyer, Kraig Worrall, Yvan Pelletier and Larry Calhoun

12:00 BUFFET LUNCH

Moderator: Gefu Wang-Pruski, Dalhousie University, Truro, NS

1:30 Reduced steroidal glycoalkaloid levels affects Solanum tuberosum resistance against pests and diseases Jamuna Risal Paudel*, Charlotte Davidson, Leslie Campbell, Cathy Clark, Lana Nolan, Jun Song, Agnes Murphy, Maxim Itkin, Asaph Aharoni and Helen H. Tai

1:45 The effects of low Levels of CIPC on seed potato performance. John Walsh*

2:00 Uncovering associations between the genomic segments and selection parameters with disease resistance and agronomic and quality traits in cultivated potato Jiazheng Yuan*, Agnes Murphy, David De Koeyer, Umesh Rosyara, Martin Lague, and Benoit Bizimungu

2:15 Identification of chromosomal locations in potatoes associated with tuberization traits affected by photoperiod using SNP markers. Maria Caraza*, David De Koeyer, Elisa Mihovilovich, Merideth Bonierbale, and Gefu Wang-Pruski

2:30 Biological predictors for tuber sweetening during long term cold storage. Jonathan Neilson*, Martin Lagüe, Susan Thompson, Frédérique Aurousseau, Agnes Murphy, Benoit Bizimungu, Virginie Deveaux, Yves Begue, Jeanne Jacobs, and Helen H. Tai

2:45 Sweet potato clonal differences in organic trial performance, dry matter content, starch content, and starch granule characteristics in New Brunswick. Xiu-Qing Li*, Suyan Niu, Ruimin Tang, Fanrui Meng, Guoqiang Fan, Qing Yang, Loretta Mikitzel, and Muhammad Haroon

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Session A:

Session Chair: Loretta Mikitzel, New Brunswick Department of Agriculture,

Aquaculture and Fisheries, Wicklow, NB

Wednesday, March 16, 2016

1:30-2:45 pm

9

Herbicides for the Control of Volunteer Potato.

Graham, G.L.* - New Brunswick Department of Agriculture, Aquaculture and Fisheries (NBDAAF) Volunteer potato (Solanum tuberosum) remains a difficult problem within a potato

rotation in New Brunswick. If tubers are not removed during the harvest procedure, they

may survive the winter and compete with the following crop, provide a host for other

potato pests and create new daughter tubers to continue the weed cycle. As with all

volunteer weeds, control begins at harvest to prevent loss of tubers and field

management to reduce tuber survival over the winter. Previous research to evaluate

herbicide control options within a cereal crop provided inconsistent results. A trial was

conducted in 2015 near Hartland, NB in a commercially managed planting of Russet

Burbank potatoes. Herbicides were applied to control the plants soon after emergence

following hilling. The grower standard treatment of MCPA amine slightly suppressed

potato growth early after application, but had minimal effects on final tuber yield, count

or size. Fluroxypyr/MCPA ester and halauxifen/fluroxypyr/MCPA ester improved

suppression but only had minimal decreases on tuber yield parameters.

Pyrasulfotole/bromoxynil, thiefensulfuron/tribenuron and

thiefensulfuron/tribenuron/MCPA amine suppressed plants early and reduced tuber

yield by 40%, mainly attributed to a smaller average tuber weight. Mesotrione treated

plants developed symptoms slowly, but offered control within the middle evaluations

followed by late regrowth. Tuber yield was reduced by 80%. The most effective

treatment, both for growth suppression and tuber yield, was glyphosate. Visual control

was over 90% on four of five evaluations and final tuber yield was over 90% less than

the untreated control. Crop competition was removed in this evaluation, but the relative

effectiveness of the herbicide treatments should be similar if evaluated under crop

competition. Applying the herbicides in a true volunteer control situation could improve

the effectiveness of herbicide treatments. Potato varieties may differ in their response to

herbicides and this could be evaluated further. Volunteer potato control in cereal

production is difficult, especially when the crop is underseeded with legumes.

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Using gene expression-based diagnostics to assess potato crop

N status: Recent progress

B.J. Zebarth* and H. H. Tai - Agriculture and Agri-Food Canada, Fredericton, NB,

Canada

We previously proposed use of gene expression in potato leaf tissue as a novel

alternative to chemical or optical tests for in-season assessment of crop N sufficiency.

Early studies examined a set of 22 genes with functions associated with N metabolism

and transport. The ammonium transporter gene was identified as a potential indicator

that increased in expression with N deficiency in the potato crop. However, further

investigation revealed that expression of the ammonium transporter gene varied widely

with time of day, making this gene unsuitable for use in diagnostic testing. The purpose

of this study was to identify other genes with expression responsive to potato N

sufficiency, but insensitive to time of day of sampling, which may be candidates for

development of a diagnostic tool. Sampling of leaf tissue was performed at four time

points during the day (0800, 1100, 1400 and 1600 h) on two sampling dates (48 and 63

days after planting) for three potato cultivars (Atlantic, Shepody, Russet Burbank). The

terminal leaflet of the last fully expanded leaf was sampled for 20 plants per plot. RNA

was extracted and genome-wide gene expression was quantified using transcriptome

sequencing. A total of 39 genes were identified which were responsive to N fertilization,

but were not affected by time of day of sampling. These genes, plus additional genes

identified as promising in previous studies (63 in all), were evaluated in one year with

the same three potato cultivars grown at five fertilizer N rates (0-240 kg N/ha). One leaf

disk was obtained from the terminal leaflet of the last fully expanded leaf for 20 plants

per plot. RNA was extracted and quantified using nCounter. The correlation between N

rate and gene expression on all three sampling dates, when averaged across three

cultivars, was |r| ≥ 0.85 for 29 genes and |r| ≥ 0.95 for 17 genes. Several of these

genes, such as amino transferase, have high levels of expression which makes them

more suitable for use as a diagnostic tool. This suggests several candidate genes exist

which could be used as a diagnostic tests to assess potato N status throughout the day.

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Can reduced N rates supplemented with foliar urea application increase nitrogen

use efficiency and potato yield and quality?

Nyiraneza Judith1* and Dave Burton2.

1.Charlottetown Research and Development Centre. Agriculture and Agri-Food Canada

(AAFC), 440, University Avenue, Charlottetown, C1A 4N6, PEI; 2. Dalhousie

University, Department of Environmental Sciences, Dalhousie University, P.O. Box 550,

Truro, Nova Scotia, B2N 5E3.

Low potato nitrogen fertilizer use efficiencies have been reported in humid and cold

environments, and the residual unused nitrogen may contribute to nitrate leaching.

This study initiated in 2014, assessed the effect of applying foliar urea (FU) during the

growing season on potato yield and quality, on N use efficiency, and on soil and crop-

based N availability indices using anion exchange membranes and chlorophyll meter

readings. In 2014, seven treatments were selected: 0N, 120N; 150N; 150N+FU, 180N,

180N+FU and 240N. In 2015, an additional treatment of 60N+FU was included. Foliar

urea rates equivalent to 6 kg ha-1 were applied 5 times for a total of 30 kg ha-1.

Applications started between 53 and 56 days after planting depending on year and were

carried out every 7 to 10 days.

In 2014, there was a significant effect of treatment on marketable yield with the control

being statistically lower than other treatments but with no significant yield increases at

the N rate above 120 kg N ha-1. Similar response was observed for total N uptake,

chlorophyll meter readings and total nitrate desorbed from anion exchange membranes.

Specific gravity was statistically lower in fertilized treatments than in the control.

In 2015, no significant yield increases were observed at a rate above 90 kg ha-1

(60N+UF) but total N uptake was statistically higher at N rate ≥ 150N kg ha-1 in

comparison with the control and 60N+UF treatments. Total nitrate measured using

anion exchange membranes and specific gravity values were comparable among

treatments.

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In 2014, the agronomic efficiency (AE, economic production per unit of nitrogen applied,

kg tuber kg-1 N) ranged between 56 and 112 kg kg-1N with 150N treatment showing the

highest value. Apparent N recovery (AR, quantity of total nutrient uptake per unit of

nitrogen applied) ranged between 21 and 61% with the highest value associated with

150N+UF. In 2015, AE ranged between 42 and 100 kg kg-1 N with 60N+UF and 150N

treatments showing higher and comparable values. Apparent N recovery ranged

between 42 and 79% with 150N treatment showing higher value.

Our preliminary 2 yr results demonstrated trends towards high AE and AR associated

with FU. The study will continue in 2016 and 2017 to validate these findings.

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Cumulative and Residual Effects of Potato Cropping System

Management Strategies on Crop and Soil Health Parameters

Robert P. Larkin - USDA-ARS, New England Plant, Soil, and Water Lab, University of

Maine, Orono, ME

Soil health has been defined as the capacity of soil to function as a vital living

system to sustain biological productivity, maintain environmental quality, and promote

plant, animal, and human health. Building and maintaining soil health is essential to

agricultural sustainability and ecosystem function. Soil and crop management practices,

such as rotations and cover crops, organic amendments, and tillage, can greatly affect

soil parameters related to soil health, as well as crop productivity and disease

development, and may provide options for more sustainable soil, crop, and disease

management. This research continues examining the effects of different 3-yr potato

cropping systems designed to address management issues of soil conservation, soil

improvement, and disease suppression, compared to standards representing a typical

potato cropping system and a nonrotation control under both irrigated and non-irrigated

conditions in long-term field trials in Maine. In this update of the research, cropping

systems were evaluated for their effects on various crop and soil health parameters

over the full term of the trials (over 8 yrs), and compared at different stages (after 1st

rotation cycle, 2006-2008; 2nd rotation cycle, 2009-2010; and after systems were no

longer maintained (2011-2012), to assess the full cumulative and residual effects of

these cropping systems over time.

In 2004, field trials evaluating different potato cropping systems focused on

different crop management approach strategies were established, to better determine

how enhanced cropping system strategies could address crop production, disease, and

soil health issues. Three specific cropping systems were established to address the

crop and soil management goals of soil conservation, soil improvement, and disease

suppression, and these were compared to a standard rotation and a non-rotation

control. The management systems consisted of: 1) Status Quo (SQ), representing a

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typical potato rotation in the Northeast (2-yr rotation: barley underseeded with red clover

as a cover crop, followed by potato); 2) Soil Conserving (SC), with limited tillage and

additional full year forage grass (3-yr, barley/timothy-timothy); 3) Soil Improving (SI),

with compost amendments (composted dairy manure, 45 Mg/ha) added each year (3-yr,

barley/timothy-timothy); and 4) Disease Suppressive (DS), featuring diverse crops with

known biofumigation or disease-suppressive capability (3-yr, Mustard green manure/

rapeseed-Sudangrass green manure/rye). Each system was also compared to a

continuous potato control (PP) and was conducted under both irrigated and non-

irrigated conditions. Data represent combined results from potato seasons following the

1st and 2nd full rotation cycles (2006-08, 2009-10), and residual effects (2011-12).

Soil Properties. At all measurement times (1st and 2nd cycle, residual), all rotations

increased aggregate stability (WSA) and water availability (soil moisture) relative to no

rotation (PP), and SI and SC increased values more than DS and SQ, with increasing

values over time (Fig. 1). Bulk density was lower in SI and SC relative to all other

systems, and lowest in SI. Total C and N were highest in SI and increased over time,

with values 35-65% greater than all other rotations (Fig. 1). Concentrations of P, K, Ca,

and Mg, as well as CEC also were highest in SI and increased over time, even after

systems were no longer managed (residual effects). All rotations increased microbial

activity and microbial biomass C relative to no rotation (PP), with increases of 25-60%,

and increasing effects over time. SI resulted in the greatest microbial response, with

activity and biomass greater than all other rotations.

Tuber yield. SI produced the greatest yield under rainfed conditions (17-49% increase

over all others) at all times, but under IRR, DS produced the highest yield (20-27%

increase) through the 2nd cycle (Fig. 2). IRR increased yield in all systems except SI

(18-27% increase), with SI essentially substituting for irrigation.Yield was lowest in the

SQ and PP systems overall. After management of cropping systems was ceased,

effects continued to be observed (residual effects). Yields were lower than previous

years, primarily due to late planting. SI and DS maintained higher yields than all others

(14-49% increases) (Fig. 2).

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Soilborne disease. IRR generally resulted in higher levels of black scurf and common

scab throughout. Black scurf incidence and severity generally increased with each

rotation cycle across all rotations, but DS reduced black scurf relative to all other

rotations through all successive stages of the study (reductions of 10-58%). SI was

generally no better than SC and SQ in reducing disease relative to PP. Overall, CS

effects on soil microbial communities (based on FAME profiles) became more

pronounced over time.

In Conclusion, cropping system significantly affected soil physical, chemical, and

biological properties, as well as tuber yield and disease development, with effects

generally becoming more pronounced over time (2 rotation cycles). Cropping system

continued to have significant effects even after rotations were discontinued (residual

effects). All rotations increased aggregate stability, water availability, microbial activity,

and yield relative to no rotation, and 3-yr rotations were superior to 2-yr for several

parameters. The SI system, which included yearly compost amendments, had the

greatest effects on soil health parameters, resulting in high yields, but only nominal

disease reduction. The DS system, which included disease-suppressive green manures

and cover crops, provided more modest improvements in soil health parameters, but

high yields and the greatest disease reduction, maintaining low disease levels

throughout study period. Cropping systems that incorporate soil health management

practices, such as use of cover crops, green manures, reduced tillage, and particularly

organic amendments, can improve soil health parameters related to soil structure,

nutrition, fertility, and water relations, which may enhance sustainability and ecosystem

function.

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Figure 1. Effects of cropping system (SQ-standard rotation, SC-soil conserving, SI-soil improving, DS-disease-

suppressive, and PP-nonrotation control) on soil moisture content, water stable aggregates, (top row graphs), and

total C and N (bottom row graphs) from initial (baseline) levels and following the 1st rotation cycle, 2nd rotation

cycle , and after rotations no longer maintained (residual effects). Data averaged over multiple years - 1st cycle,

2006-2008; 2nd cycle 2009-2010; Resid. (subsequent) 2011-2012.

Figure 2. Effects of cropping systems (SQ-standard rotation, SC-soil conserving, SI-soil improving, DS-disease-

suppressive, and PP-nonrotation control) and irrigation (IRR=irrigated; NON=rainfed, no irrigation) on potato tuber

yield after A) the 1st rotation cycle, B) 2nd rotation cycle , and C) subsequent plantings (residual effects). Data

averaged over multiple years - 1st cycle, 2006-2008; 2nd cycle 2009-2010; Resid. (subsequent) 2011-2012. Bars

topped by the same letter are not significantly different from each other based on ANOVA and Fisher’s protected

LSD test (p<0.05).

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Spatial variation in soil bacterial and fungal communities in a

commercial potato field

Claudia Goyer*, Sara Neupane, Bernie J. Zebarth, Sheng Li, and Sean Whitney -

Agriculture and Agri-Food Canada, Fredericton Research and Development Centre,

Fredericton, NB

Soil properties are known to vary within landscapes. However, the variation in

diversity of soil microbial communities within landscapes, and how this variation is

affected by topographic features and soil properties, is poorly understood. To date, a

primary limitation has been the availability of cost-effective tools to assess soil microbial

diversity. Next generation sequencing now provides a practical means of characterizing

soil microbial communities on large numbers of samples. In this study, soil samples

were collected from a transect approximately 1100 m long in a commercial potato field

in New Brunswick. The transect included 83 sampling points, with distances between

sampling locations varying from 2 to 50 m. The transect was located in a landscape of

rolling topography with a relief of approximately 24 m. Most sampling locations were

located in upper and mid-slope landform elements. Slope gradient at the sampling

locations ranged from approximately 2 to 12%, and in many cases the direction of

maximum slope was approximately perpendicular to the transect. A composite soil

sample from 0-15 cm depth was collected from the potato hill at each sampling location

late in the growing season under relatively dry soil conditions. Soil physico-chemical

property measurements included soil texture, soil moisture, pH, organic carbon and total

nitrogen. Soil pH was variable, and ranged from 4.3 to 7.0. Soil texture was less

variable with sand content ranging from 310 to 550 g kg-1 and clay content ranging from

85 to 175 g kg-1. Soil pH strongly negatively correlated with slope gradient (R2 = - 0.73,

p < 0.001), presumably due to soil erosion by tillage and water exposing low pH

subsoils.

Diversity of soil microbial communities was evaluated by amplicon sequencing of

the bacterial 16S rRNA genes and the fungal internal transcribed sequence (ITS) using

the Illumina MiSeq sequencing system. Sequences were analyzed in Mothur and Qiime

18

softwares using Ribosomal Database Project (RDP) and UNITE (Unified system for the

DNA based fungal species v7) reference databases for assigning the consensus

taxonomy of bacterial and fungal communities, respectively.

When averaged over the 83 sampling points, Proteobacteria, Actinobacteria and

Acidobacteria were the dominant bacterial phyla with relative abundances of 32, 21 and

15 %, respectively. Phyla such as Firmicutes, Verrucomicrobia, Chloroflexi,

Planctomycetes and Bacteroidetes were present at each sampling point but were in low

(< 10%) relative abundance. Factors i.e. topographic parameters (slope gradient and

curvature) and soil physico-chemical properties (soil pH, texture, organic carbon and

total nitrogen) potentially influencing the variation in bacterial community diversity were

determined using a canonical correspondence analysis (CCA). The result revealed that

soil pH was the most important factor explaining the variance in bacterial community

diversity (R2 = 0.85, p < 0.001), followed by slope gradient (R2 = 0.52, p < 0.001).

Organic carbon, clay and soil water content explained some of the variance in bacterial

diversity but to a lesser extent with R2 ranged 0.2 to 0.4. Moreover, total bacterial

diversity decreased with decreasing soil pH as measured by Shannon-Weaver Index

(R2 = 0.72, p < 0.0001). Overall, these results suggested that soil pH was the major

driver for bacterial community diversity in the experimental field, and that the soil pH

was in turn closely related to slope gradient.

Ascomycota and Basidiomycota were two dominant fungal phyla with average relative

abundance of 69 and 16 % respectively when averaged over all sampling points. Low

abundance phyla were Zygomycota (7%), Glomeromycota (1%) and Chytridiomycota

(3%). A CCA between fungal community diversity and topographic parameters (slope

gradient and curvature) or soil physico-chemical properties explained only 8% of the

variance in fungal community diversity and none of the measured factors were

significant. This result indicated that unknown topographical or soil properties affect the

diversity of fungal community in the transect or that fungal community diversity is

controlled at another scale. Unlike bacterial diversity, fungal community diversity

measured by Shannon-Weaver Index did not change with soil pH gradient, which was

consistent with result from multivariate analysis.

19

Results of this study indicate that soil bacterial communities vary in systematic

and predictable patterns in this agricultural field in response to variation in topography

and soil properties. In contrast, the controls on the spatial pattern of soil fungal

community structure could not be identified in this study.

.

20

Session B:

Session Chair: Brian Beaton, PEI Department of Agriculture and Fisheries, PE

Wednesday, March 16, 2016

3:30-5:00 pm

21

Can we find the “right” compost for New Brunswick potato production?

Carolyn Wilson1,2*, Bernie Zebarth2, David Burton1, Claudia Goyer2

1 Dalhousie University Faculty of Agriculture, Truro, NS

2 Fredericton Research and Development Centre of Agriculture and Agri-Food Canada, Fredericton, NB Potato (Solanum tuberosum L.) is an important arable crop in the province of New

Brunswick, Canada. However, the productivity and quality of potato fields has been

declining for decades due to soil erosion and declining soil organic matter (SOM).

Addition of compost may be an effective means to rapidly increase SOM, and thereby

increase productivity. This study compares five composts from a diversity of sources

with a no compost control for their effects on tuber yield and soil quality. The compost

products primarily contained wood wastes, poultry manure, or marine feedstocks, and

the C:N ratio ranged from 10 to 63. High rates of compost (45 Mg ha-1, dry weight) were

fall-applied to small field plots in a randomized complete block design with four

replicates. Tuber yield and size distribution were determined. Measured soil quality

indictors included: aggregate stability, bulk density, saturated hydraulic conductivity, soil

water content, soil organic carbon, resistance to penetration, and rainfall infiltration as

measured with a Cornell Sprinkle Infiltrometer. Soil quality was significantly affected by

compost treatments in the growing season following application as indicated by a

decrease in bulk density and an increase in saturated hydraulic conductivity and soil

organic carbon. Compost products with lower ash (higher organic matter) tended to

result in greater improvements in soil quality. The application of compost also resulted

in significant differences in plant nitrogen availability. However, changes in soil quality

did not translate into an effect on tuber yield. The lack of a measurable yield response

to compost treatments was attributed to a combination of generally good initial soil

quality and favourable growing season soil moisture conditions. Overall, this study may

help find the “right” compost for potato production by identifying properties of compost

which will be most suitable for use in potato production systems to enhance crop

productivity and sustain soil quality.

22

The Effect of Compost on Russet Burbank Yield and Quality

Gilles A. Moreau* (McCain Foods (Canada), Saint Andre, NB),

Bernie Zebarth (AAFC, Fredericton, NB)

The Canadian potato industry is rapidly losing access to global markets for potato

products. The situation is particularly dire in New Brunswick where the increase in

production costs of the past decade has not been associated with an increase in yield.

Compost has been demonstrated to increase tuber yield over short time periods. Porter

et al. (1999) reported an average yield increase of 21% over three years in Maine from

application of waste potato compost plus beef manure with sawdust bedding. Also in

Maine, annual application of dairy manure compost in combination with a three-year

potato rotation (referred to as a “soil improving” production system) resulted in an

average yield increase of 24% compared with a conventional two-year potato rotation

with no organic amendment under rain-fed production (C.W. Honeycutt, unpublished

data). Similarly, Bernard et al. (2014) reported yield increases of 9-15% from use of a

conifer-based compost amendment in Maine.

The overall objective of this project is to evaluate the potential to overcome limitations to

potato tuber yield in New Brunswick by improving soil health with three consecutive

annual applications of compost.

Field-scale trials are being conducted on fields under commercial potato production in

New Brunswick, primarily in the Grand Falls and in the Florenceville/Woodstock areas.

In most cases, field sites are located on farms using two-year potato rotations. Three

sites were established in the spring of 2014 and nine sites in the fall of 2015. At each

site, a portion of the field will receive compost applications for three consecutive years

at a rate of approximately 27 t/ha on a dry weight basis (equivalent to approximately 45

t/ha on an as-received basis assuming 60% dry matter content). The compost is applied

as a single strip, the full length of the field. The material is produced by Envirem

Organics Inc. at their Green River composting facility using waste from the forestry and

poultry industries. The compost was either disked or harrowed in prior to planting the

potato crop and the fertilizer program was kept the same in the control and amended

sections of the field.

23

In-season measurements included emergence rate, plant and stem counts, petiole

sampling for petiole nitrate, P and K, leaf area index using a LAI 2200 instrument, leaf

chlorophyll content using a SPAD-502 meter and plant biomass to calculate the crop

Nitrogen Nutrition Index. Continuous in-season monitoring of soil water content and

temperature with EM50 data loggers and 5TE sensors was performed at six sampling

locations in each of two fields both seasons. Tuber yield was measured by manually

harvesting six to fifteen paired sampling locations (i.e. with and without applied

compost) in each field. Sampling sites were selected to reflect the range of variation in

landscape position.

A compost analysis performed on a number of samples collected just before field

application supplied the following results: dry matter – 45 to 50%; pH – 7.5 to 8.4; C: N

ratio – 30:1; total nitrogen – 0.37%; phosphorus – 0.21%; potassium – 0.50%; calcium –

3.1%.

Results of petiole sampling conducted from 45 to 100 days after planting suggest the

compost does not consistently increase petiole nitrate concentrations and that

concentrations are within the optimum zone (Porter and Sisson 1991) for Russet

Burbank.

Averaged over two years and nine sites, a one-time compost application at the rate of

27 t/ha dry weight resulted in a two point decrease in specific gravity, a slightly lower

incidence in hollow heart and sunburn, a small increase in the proportion of 10-ounce

and No.1 tubers, and a marketable yield increase of 16 cwts/acre. However, important

site and zone responses were noted with higher yielding sites responding better to

compost application.

A one-time application of compost at the rate specified above did not return an

economical benefit in Year 1. More work needs to be done to determine the potato yield

response to multiple applications, assess the treatment effect on the grain rotation crop,

and evaluate the long-term residual effect of the treatment.

24

Effect of Compost on Small Grain Grown in Rotation with Potatoes

Daniel Savoie (NBDAAF, Grand-Falls, NB)* and Gilles A. Moreau (McCain Foods

(Canada), Saint Andre, NB),

Compost has been applied in delimited area of three potato field grown in rotation with

small grain in the Potato Belt of New-Brunswick; fields were located in Florenceville,

Drummond and St-André, NB. Compost have been applied at the rate of 45 t/ha on wet

basis or 27 t/ha on a dry matter basis in the Spring and Fall 2014 for the fields in

Florenceville and Drummond and only in the Spring 2014 for the field in St-André.

Wheat, oats and barley were grown in Florenceville, Drummond and St-André

respectively in 2015 following Russet Burbank cv processing potatoes in 2014.

Each cereal species have been grown with the respective management practices of the

individual grower without any difference in the compost and non-compost section of

each field.

As close to mechanical harvest as possible each site were manually harvested with the

straw using a circular quadrat of 1 m2. A total of eight paired samples have been taken

at each site, eight in the compost and eight in the non-compost section. Samples were

stored in a well aerated building before being threshed by a HEGE Small Plot Combine

two to three weeks after manual harvest. All samples have been weighed and graded

and a T-test has been performed.

Only one site showed higher yield, test weight and crop value with a significant

difference for compost when compared to the non-compost strip. In the two other sites

there was no significant differences for all the criteria evaluated, but a trend in the

compost section for higher yield, test weight, thousand kernel weight and crop value.

25

Effect of Compost on Potato Soil Physical and Biological Properties

Pat Toner * (New Brunswick Agriculture, Aquaculture and Fisheries, Fredericton, NB)

Gilles A. Moreau (McCain Foods (Canada), Saint Andre, NB) Bernie Zebarth (AAFC,

Fredericton, NB)

From the BMP work done at field scale comparing compost to no compost in 2014 and

2015 (McCain Foods/AAFC), the Province was given the opportunity, post hilling to

conduct infiltration and runoff comparisons among the two treatments using the Cornell

Infiltrometer. In addition to this, each waypoint tested also had several soil cores

extracted for subsequent biological respiration testing using the Solvita 24hr CO2 burst

kit as provided from Woods End Labs. McCain Foods provided volumetric soil moisture

data and AAFC provided soil aggregate stability data using conductance measurement

and wet sieve analysis respectively.

It was found that the operation of the Cornell Infiltrometer was time consuming, i.e. one

hour or more to get readings at one point. Also, it presented challenges in the rate of

rainfall it delivered when air temperatures became hotter over the course of the day.

That being said, a constant trend in reduced runoff and increased infiltration could be

seen on compost treated portions of the field. This finding was further backed up on a

statistically significant basis when compared soil moisture data that showed compost

had a higher level of soil moisture retained from rainfall events and thus available for

use by the crop.

Soil aggregate stability showed a significant increase with the use of compost as did soil

respiration from Solvita burst tests on samples from both years. These two indicators

would suggest improved soil structure and biological activity from compost additions.

Given that the sample fields only received compost once to date, 25 t/ac, as is; further

analysis of soil physical and biological properties will be needed to determine the long

term benefits of compost to potato production.

26

Spatial and temporal variation of selected soil fertility parameters in

Prince Edward Island

Judith Nyiraneza1*, Sherry Fillmore2, Barry Thompson3, Kyra Stiles3, John MacLeod3, and Yefang Jiang1.

1 Agriculture and Agri-Food Canada, 440 University Avenue, C1A 4N6, Charlottetown,

PE, CA. 2 Agriculture and Agri-Food Canada, 32 Main Street, B4N 1J5, Kentville, NS,

CA. 3 PEI Department of Agriculture and Fisheries, PO Box 2000, C1A 7N8,

Charlottetwon, PEI, CA.

Soil fertility decline is a major issue in intensively low residue managed systems but the

extent to which rotations systems affect the trends needs to be ascertained to designate

appropriate mitigation strategies. This long-term study (1998-2012) combined

chronosequential and soil grid samplings on more than 500 geo-referenced sites every

cycle to analyze trends in soil fertility in Prince Edward Island (PEI), Canada. Crop

grown at each sampling site was recorded every spring and site were characterized as

either potato-, grain-, and forage- based system depending on the number of

occurrence of each crop during the study period. Geospatial maps were also produced.

Trends over time of selected soil fertility parameters were assessed and compared

among cropping systems. Overall SOM mean was 3.5 %, 3.2%, and 2.8% in forage-,

grain-, and potato-based system, respectively. The value under forage-based system

was statistically higher in comparison with grain- and potato-based systems. The SOM

was lower under potato- than under grain-based system. Averaged across all three

main crops, SOM declined by 25%, soil pH by 5%, magnesium by 23%, and sulfur by

38%. Conversely, phosphorus levels increased by 9% under potato-based system in

comparison with initial values. Causal effects of the observed trends as well as

potential mitigation strategies will be discussed.

27

Evaluation of 4R Fertilizer Strategies on the

Performance of PEI Potatoes

Steve Watts, Genesis Crop Systems Inc., Hampton PE

The Farming 4R Island Initiative was introduced to the PEI Potato Industry by a

stakeholder group including Fertilizer Canada, PEI Federation of Agriculture, PEI

Departments of Agriculture & Environment, PEI Potato Board and the Kensington North

Watershed Association in 2013.

The main objective of the initiative was to evaluate effects of various 4R (Right

Product®, Right Rate®, Right Time®, Right Place®) fertilizer best management

practices (BMPs) on the yield, quality, economic value and environmental impact of

potato production in PEI.

BMPs evaluated during the 2013-15 growing seasons included split application of

Nitrogen into 2-3 applications, reduction of P2O5 based on Soil Phosphorous Saturation

Indices, removal of KCl from the planter blend and upward adjustment of MgO. All trials

were implemented as split field comparisons and compared with cooperating growers’

standard practices (GSP) for fertilization of potatoes under PEI conditions.

Results obtained from 32 field scale trials (5 -2013, 13-2014, 14-2015) support adoption

of these BMPs in that the majority of sites evaluated produced crops with equal or better

economic value, higher tuber specific gravity and reduced levels of soil residual NO3-N

following crop harvest where 4R strategies were incorporated.

Project activities will continue in 2016 and include identification and evaluation of

concepts that may assist PEI producers in improving potato crop yields, quality and

profitability while lessening the Industries’ environmental footprint.

28

Session C:

Session Chair: Christine Noronha, AAFC-CRDC, Charlottetown, PE

Thursday, March 17, 2016

8:30-9:45 am

29

Quantifying differential spread of three PVY strains in the field: Potential

explanations for the recent increased prominence of PVYNTN

Tyler MacKenzie1*, Jacques Lavoie2, Janet McLaughlin2, Mathuresh Singh1

1Agricultural Certification Services Inc., 1030 Lincoln Road, Fredericton, NB, Canada

E3B 8B7. 2New Brunswick Department of Agriculture, Aquaculture and Fisheries, 39

Barker Lane, Wicklow, NB, Canada E7L 3S4.

The spread of Potato virus Y (PVY) is a major concern in many potato growing areas

around the world, including New Brunswick. Stringent seed certification systems have

been quite successful at keeping virus inoculum low in planted tubers, but even low

seed-borne virus, and other sources can allow for significant on-farm PVY spread. In

the field, PVY is spread between potato and other host plants by aphids. Important

techniques to control on-farm PVY spread include the frequent spraying of mineral oil

and insecticides to deter the aphids, and removing symptomatic plants (roguing).

Recent changes in the populations of different PVY strains, observed both in New

Brunswick and around the world, have challenged these typical control methods. In New

Brunswick, PVY exists in three major strains: PVYO, PVYN:O and PVYNTN. Traditionally,

the "ordinary" strain PVYO has been most dominant in the population, though in many

regions recently it has been displaced by the latter strains, particularly PVYNTN. In our

New Brunswick research fields, we found PVYNTN represented 5% and 12% of PVY

samples tested in 2009 and 2010, which rose to 67% and 61% in 2014 and 2015,

respectively. This rapid change in strains prompted us to design experiments to directly

investigate the mechanism(s) driving it. In our first experimental trials (2014) we

observed strain-specific PVY spread from random mixes of strains represented in high-

PVY seed sources (3.3% PVY Russet Burbank and 2.7% PVY Goldrush), both cases

initially dominated by PVYNTN. Of the initial planting inoculum, 62% and 76% of virus

was PVYNTN in the two trials, respectively; together in these trials, 2500 marked initially

virus-free plants were followed to monitor on-farm PVY spread. By the end of the

season, 82% and 84% of newly infected plants carried PVYNTN, and in the harvested

tubers, 81% and 88% were PVYNTN, respectively. In 2015, two trials were conducted

30

with a hand-planted standardized mix of strains, Goldrush at 33.3% of each strain, and

Russet Burbank at 40% PVYO and PVYNTN and 20% PVYN:O. Even in these more

controlled trials, PVYNTN proportion of harvested tubers in newly infected plants rose

from 33.3% to 58% and from 40% to 69% in the two trials. PVYNTN infected plants had

more tubers carrying virus, 71% versus 61% in PVYO infected plants. Also, PVYNTN

plants had more large tubers (>4 ounces), averaging 4.7 per plant versus 3.4 in PVYO.

These differences in size, number and rate of tuber infection could in part explain the

year-to-year rise in PVYNTN, though several other mechanisms must be at work to

explain why PVYNTN spreads more effectively between plants during the growing

season. We have developed several hypotheses related to the plant-aphid-PVY strain

interaction that will be tested in our upcoming 2016 field trials.

31

The Use of Mineral Oil for the Management of Potato Virus Y: Deciphering the

Mode of Action.

Sébastien Boquel1,2*, Jianhua Zhang2, Marie-Andrée Giguère2, Catherine Clark2,

Xianzhou Nie2

1. S.I.P.R.E - Comité Nord, Rue des Champs Potez, 62217 Achicourt, France.

sebastien.boquel@agr.gc.ca 2. Fredericton Research and Development Centre, 850

Lincoln Rd, Fredericton NB E3B 4Z7, Canada.

Potato virus Y (PVY) is found worldwide and is an important concern in Canada. It is

transmitted from plant to plant exclusively by aphids in a non-persistent manner and can

result in important economic loss to the producers. The only reliable method known to

reduce the spread of PVY in potato seed production is a weekly application of mineral

oil in addition to plant “clean” tubers. While the efficacy of mineral oil was demonstrated

in other countries a long time ago, mineral oil has only been available to Canadian seed

potato producers for the last five years. Mineral oil is currently used to reduce the

spread of PVY in seed potato fields but its mode of action is still poorly known.

Improving our understanding of the mechanism of inhibition of PVY infection by mineral

oil is a key component in accurately advising seed potato growers on how to efficiently

use mineral oil.

The objective of this work was to investigate the mode of action of mineral oil for better

management of PVY disease. A global approach was used to understand the effect of

mineral oil on the spread of PVY by studying all interactions between aphid, potato and

PVY. During four summer growing seasons, potato fields were sprayed with mineral oil

at 0 L ha-1 (Control), 10 L ha-1 (recommended dose) and 15 L ha-1 (variable dose). The

results showed that mineral oil was effective in protecting potato plants against PVY

spread without negative effects on foliage growth, canopy closure and yield. The

efficacy of mineral oil was also enhanced when high doses of mineral oil were applied

onto the plants. A strong effect on PVY acquisition by aphid was highlighted under

greenhouse conditions but not under field conditions. However, a strong reduction of

32

PVY transmission as well as PVY quantity in leaves was observed under field conditions

in plants that were treated with mineral oil compared to untreated plants. These results

suggest that the mode of action is mainly linked to the effect of the interaction between

PVY and the potato host plant. Investigations are currently underway to confirm that the

main mode of action of mineral oil is linked to the impact on the replication and/or

accumulation of the virus within plants.

33

Identification and characterization of an Alfalfa mosaic virus isolate in potatoes

exhibiting internal necrosis

Xianzhou Nie*1, David De Koeyer

1 , Zengenni Liang

1, Virginia Dickison

1, Mathuresh

Singh2, Gary Hawkins3

1 Potato Research Centre, Agriculture and Agri-Food Canada, 850 Lincoln Road,

Fredericton, New Brunswick, Canada E3B 0E2; 2 Agricultural Certification Services,

1030 Lincoln Road, Fredericton, New Brunswick, Canada E3B 8B7; 3 McCain Produce,

8734 Main Street, Unit 1, Florenceville, NB, Canada E7L 3G6 (GH)

RT-PCR tests for 10 common potato viruses detected Potato virus S (PVS) and Potato

virus Y tuber necrosis strain (PVYNTN) in potato tubers exhibiting extensive internal

necrosis in potato cultivar Innovator. Progeny plants developed mosaic symptoms and

tested positive for the above viruses/virus strain by ELISA, RT-PCR and bioassay. As

expected, tubers from these plants developed severe internal necrosis. However, single

or mixed infections with PVS and various strains of PVY including PVYO, PVYN, PVYN:O

and PVYNTN on plants of Innovator did not cause any visible internal or external

necrosis, suggesting that an unusual virus/virus strain might be the causal agent of

internal tuber necrosis. Using next generation sequencing for detection of virus-derived

small RNAs, Alfalfa mosaic virus (AMV), in addition to PVS/PVY, was detected in the

original samples. After passing through tobacco and a PVY-resistant potato breeding

line, AMV was purified. Inoculation of various potato varieties including Yukon Gold,

Chieftan, Russet Burbank, Shepody, Rochdale Gold-Dorée, and Innovator with the

purified AMV induced varying degrees of calico-symptoms typical for the virus.

Examination of tubers from the inoculated plants indicated the presence of internal

necrosis in some of the varieties including Innovator and Shepody. The complete

genome of the isolate, comprising of three genomic RNAs of 3643, 2594 and 2038

nucleotides, was determined and characterized. Phylogenetic analysis of the AMV with

those retrieved from databases indicated that at least two clustering groups can be

found for each of the three genomic RNAs in AMV.

34

The Use of Cryotherapy for Elimination of Potato Virus S (PVS) from Tissue

Cultured Potato Plants of Potato Seedling PR07-11-1

Robert Coffin3*, Andrew McCartney1, Xiuying He1, Mathuresh Singh2, Angela Gallagher2

and Joyce Coffin3

1. Maritime Innovation Ltd., Sussex, N.B., E4G 2V5, 2. Agricultural Certification Services,

Fredericton, N.B., E3B 8B7, 3. Privar Farm Inc., North Wiltshire, PEI, C0A 1Y0

Investigation of cryotherapy procedure for eliminating PVS from in vitro potato plantlets

Privar Farm Inc. is a private potato breeding program on Prince Edward Island. A

promising seedling, PR07-11-1, (i.e., high yielding, long type tubers, russet skin, good

table and processing traits) was placed in the virus freeing program at Agricultural

Certification Services, Fredericton, N.B. Despite long-term exposure of tissue cultured

plantlets to thermotherapy and chemotherapy (Ribavirin) treatment, difficulties were

encountered to obtain plantlets that were free of Potato Virus S (PVS). It is recognized

that PVS is one of the most difficult viruses to remove from potato plants and is often

referred to as a “sticky” virus. In discussions with Dr. Dave Douches (potato breeder,

Michigan State University), it was pointed out that cryotherapy is a helpful technique to

remove PVS from in vitro potato plantlets. Hence, the use of cryotherapy was

investigated with the objective of removing PVS from the potato seedling PR07-11-1.

Background and Theory

As part of the federally regulated Seed Potato Act, all potato varieties propagated for

production in Canada must originate from disease-free (particularly virus free) tissue

culture plantlets. The traditional method of obtaining virus free material (nuclear status)

through meristem culture is laborious, technically challenging and doesn’t always result

in plants free of viruses due to the small nature of the meristem ex plant material. A

modern approach using thermotherapy and chemotherapy is faster, easier, and more

effective and is now the preferred method for virus elimination. However, certain

varieties may not respond well to thermotherapy and chemotherapy treatments as

evidenced by the continued detection of some viruses, particularly PVS, even after

harsh treatment with heat and chemicals.

Potato virus S (PVS) is a common virus found worldwide yet plants infected with PVS

often show mild or no symptoms in the foliage compared to major damage of foliage

35

upon infection with PVY, PVX and/or Leaf Roll virus (PLRV). PVS does not cause major

yield losses and field-grown seed is not always routinely tested in some jurisdictions as

it is not considered to be economically important. Canada and a few other countries,

however, have a zero tolerance for PVS in nuclear stocks. To meet nuclear status in

Canada in vitro plantlets must also test negative in several audits for Bacterial Ring Rot

(BRR), Potato Spindle tuber viroid (PSTVd), and potato viruses PVA-M-S-X-Y-LR,

potato latent virus (PotLV; also known as Red LaSoda virus) and Potato Mop Top virus

(PMTV). In this work, we describe two virus freeing methods and discuss the

advantages and limitations of each.

Virus freeing potato plantlets using chemotherapy and thermotherapy

A routine practice for virus freeing potatoes is to use a combination of heat therapy and

chemotherapy (i.e., Ribavirin). Ribavirin is known to inhibit synthesis and replication of

both single-stranded and double-stranded RNA viruses (Dawson and Lozoya, 1984).

The combination of Ribavirin and high temperatures (i.e., >36oC) inhibits the movement

of virus into new shoot growth. New shoot tips, therefore, have higher chances of being

virus free. These new shoot pieces are then excised, subcultured and tested for the

presence of virus and BRR.

The method for freeing potato varieties using chemotherapy and thermotherapy is

described briefly as follows. Tubers from potato varieties to enter the nuclear program

are sprouted and the tips excised, surface sterilized and maintained in tissue culture on

Murashige and Skoog (MS) media supplemented with 30g/L sucrose and 6g/L agar.

Plantlets are maintained under low light conditions at a temperature of 20-24oC. To

begin the chemotherapy treatment, standard potato MS media is prepared to which

0.03mg/ml of filter sterilized Ribavirin (Sigma #R9644) is added. The top two nodes

from ten plantlets are excised and placed onto the Ribavirin-containing media and

grown for several weeks under a 16hr light – 8hr dark photoperiod at 20-24oC. After the

plantlets have produced several nodes of growth they are then moved to higher heat for

the thermotherapy treatment which consists of alternating light/dark regimes of 4hrs

each at 31oC and 36oC, respectively. The plantlets will eventually begin to die back until

only a small portion remains green and viable. When this is observed the top two nodes

from each plant are excised and cultured on standard MS media under standard

growing conditions. Once plantlets have grown to several nodes in length they are

36

multiplied so there is sufficient plant material to perform a full nuclear audit (i.e., test for

BRR, PSTVd, PVA-M-S-X-Y-LR-PotLV and PMTV). Plantlets are also further screened

for the presence of any bacteria or fungi using Richardson’s Liquid Media (RLM),

Nutrient Both (NB) and Potato Dextrose Agar (PDA).

Virus freeing potato variety PR07-11-1 using cryotherapy

The chemotherapy and thermotherapy procedure was effective in clearing most viruses

from variety PR07-11-1 but PVS proved stubbornly difficult, necessitating the need for

alternative approaches. Previous reports demonstrated that a procedure using ultra cold

temperatures was effective in freeing plants of these more difficult to eliminate viruses

(Wang et al., 2009). The technique, called cryotherapy, uses liquid nitrogen to freeze

tissues down to a temperature of -196oC and then regenerate new plants from the

tissues after thawing.

The cryotherapy technique works due to the way in which plants grow. The above

ground growing part of the plant originates from the shoot apical meristem which is

characterized by small densely packed and rapidly dividing cells. As cells of the apical

meristem expand upwards, the cells below develop into the tissues and organs

recognizable of a plant. Unlike the small, densely packed cells of the apical meristem,

the cells below are larger, more vacuolated and are connected to the plant’s vascular

system. Viruses, which are transported throughout the plant via the vascular system,

can enter into these cells but are otherwise excluded from the apical meristem cells due

to the lack of vascular connections. The approach of the traditional meristem culture

technique for virus elimination attempts to cut away the apical meristem without

including the larger cells below it that potentially carry viruses. This is nearly impossible

to do in practice because meristems are so small even when magnified with a

microscope. The cryotherapy technique overcomes this limitation by taking the entire

shoot tip (approximately 1 mm in length) and incubating the tips briefly in a

cryoprotectant solution. The solution acts to withdraw water from the small densely

packed apical meristem cells but is inadequate to withdraw much water from the larger

vacuolated cells below. When the shoot tips are rapidly frozen in liquid nitrogen the

apical meristem cells are protected while all the other cells of the shoot tip piece that

potentially carry virus are not protected and so they die. After the freezing step, the

37

shoot tips are thawed and regenerated into new plants. Since the probability of virus

containing cells surviving the freeze/thaw process is low, the new plants regenerated

from the shoot tips are highly likely to be free of virus. Further testing of the regenerated

plants is done to confirm this.

The cryotherapy procedure used to clear PVS from PR07-11-1 was adapted from Kim

et al. (2006) and Wang et al. (2006). Briefly, virus-containing PR07-11-1 tissue culture

plantlets were initiated from tubers provided by Privar Farm in the laboratory of

Agricultural Certification Services (Fredericton, NB) and transferred to Maritime

Innovation Limited at the 4-6 leaf stage of development to begin the cryotherapy

procedure to eliminate PVS and other viruses. Shoot pieces containing the apical

meristem were excised from several tissue culture plants using scalpels and a

dissecting microscope and incubated in a cryoprotectant solution of MS + 0.3M sucrose

solution for 8 hrs on a rotary shaker at 75 rpm. After the 8 hrs the liquid was removed

and the shoot pieces were then incubated in a second cryoprotectant solution of MS +

0.7M sucrose solution for 18 hrs. The solution was removed the following day and the

shoot pieces incubated in a third cryoprotectant solution for 20 min. Next, strips of

aluminum foil (7 x 20 mm) were prepared and 5-7 drops of the cryoprotectant solution

were added to each strip. One shoot piece was added to each drop on the aluminum foil

strips and the strips placed immediately in liquid nitrogen for 1 hr. During the incubation

in liquid nitrogen, a fourth cryoprotectant solution of MS + 0.8M sucrose was prepared

and preheated to 40oC. Following the incubation in liquid nitrogen, aluminum foil strips

containing 5-7 shoot pieces were placed immediately in the preheated MS + 0.8M

sucrose solution and incubated for 30 sec. The liquid was replaced with room

temperature MS + 0.8M sucrose solution and the shoot pieces incubated for an

additional 30 min. All shoot pieces were then cultured on meristem culture media under

low intensity light for 7 days and then transferred to standard culture conditions.

Approximately 20% of the shoot pieces survived the cryotherapy procedure and were

viable following transfer to meristem culture media as evidenced by callus formation

originating from the apical meristem. Shoot regeneration was visible from the callus

after several months of incubation and, in total, 8 plantlets were successfully

regenerated. Each of the 8 lines were further multiplied to produce sufficient plant

material for ACS to conduct a full nuclear audit. All 8 of the lines tested were determined

38

to be virus free.

Conclusions

The cryotherapy process takes longer and is more challenging than the thermotherapy

and chemotherapy approach; however, it appears to be very effective in eliminating

viruses from plant tissues especially for viruses that are otherwise difficult to remove. It

should be noted that plantlets regenerated from callus via shoot organogenesis may (in

rare cases) have genetic mutations caused by somaclonal variation. It is recommended

that a couple of rounds of field testing be conducted to ensure the variety remains true

to type. Toward this end, eight plants of each of the 8 lines of PR07-11-1 seedlings

were planted in the field at Privar Farm Inc. on PEI in 2015. No differences were noted

in plant growth during the summer and no differences were noted in tubers at harvest.

Tubers from each line will be planted in 2016 for additional assessments.

References

Dawson, W.O. and Lozoya-Saldana,H. (1984) Examination of the mode of action of

Ribavirin against Tobacco Mosaic Virus. Intervirology. 22: 77-84.

Kim, Haeng-Hoon; Yoon, Ju-Won; Park, Young-Eun; Cho, Eun-Gi; Sohn, Jae-Keun;

Kim, Tae-San and Engelmann, Florent. (2006) Cryopreservation of potato cultivated

varieties and wild species: Critical factors in droplet vitrification. CryoLetters. 27:223-

234.

Wang, Qiaochun; Liu, Yong; Xie, Younghong; You, Misa. (2006) Cryotherapy of potato

shoot tips for efficient elimination of Potato Leafroll Virus (PLRV) and Potato Virus Y

(PVY). Potato Research. 49:119-129.

Wang, QC., Panis, B., Engelmann, F., Lambardi, M., and Valkonen, J.P.T. (2009).

Cryotherapy of shoot tips: a technique for pathogen eradication to produce healthy

planting materials and prepare healthy plant genetic resources for cryopreservation.

Annals of Applied Biology. 154:351-363

39

Utilization of new sources of dual resistance to PVY and

late blight in potato breeding.

Benoît Bizimungu1, Agnes Murphy1, Ramona Thieme2 and Thomas Thieme 3

1Agriculture and Agri-Food Canada, Fredericton, NB; 2 Julius Kuhn-Institut (JKI),

Federal Research Centre for Cultivated Plants, Germany, and 3 BTL Bio-Test Labor

GmbH Sagerheide, Germany.

Host plant resistance provides a sustainable and cost-efficient disease control as part of

an integrated pest management system by reducing pesticide applications on crops.

Therefore resistance breeding plays an important role in many cultivar development

programs. Late blight and PVY are among disease priorities in our potato breeding

program. Genetic resistance is usually found in wild Solanum species, and extensive

pre-breeding work is needed to incorporate it into adapted parental lines. Current

breeding efforts include the use of new parental material with multiple disease

resistances and identifying resistant selections. The availability of new germplasm

combining resistance to PVY and late blight offers the prospect to breed dual resistance

into a single cultivar. A great number of progenies were derived from crosses involving

resistant parents and elite parental germplasm. Multi-traits selection is conducted to

identify resistant clones with suitable agronomic and quality characteristics required for

their adoption by the industry. The availability of diagnostic molecular markers is

expected to play a greater role in helping to identify resistant selections early in the

breeding program and to avoid undesirable crosses.

40

Session D:

Session Chair: Robert Larkin, USDA-ARS, Orono, ME

Thursday, March 17, 2016

10:30 am - 12:00 pm

41

Study of Verticillium pathogens in potato production systems in the Maritimes

Gefu Wang-Pruski1, Tudor Borza1, Rick Peters2, Xingxi Gao1, Yahui Liu1, Kim Best3,

Kris Pruski1, Brian Beaton4, Zenaida Ganga5, Dorothy Gregory2

1Faculty of Agriculture, Dalhousie University, Truro, NS; 2AAFC, Charlottetown, PE

3Prospect Agri-Services Cambridge Station, NS; 4PEI Department of Agriculture and

Fisheries, Charlottetown, PE; 5Cavendish Farms research Division, Summerside, PE

Verticillium pathogens cause early senescence of plants due to clogging of vascular

tissue, a symptom called Verticillium wilt. Verticillium contributes to early dying

syndrome (EDS) in potato crops which can significantly reduce yields. In the Maritime

Provinces of Canada, Verticillium wilt is believed to be caused by two species, V.

dahliae and V. albo-atrum. In order to deal with EDS, Verticillium wilt has to be

controlled by either fumigation or fungicides. In PEI, since the ban of fumigation

practices, Verticillium wilt has become more severe over the years, and yield reduction

has been observed on many farms. This presentation will provide some detailed results

from four collaborative research projects that are focusing on pathogen identification

and quantification, pathogen distributions in the region, integrated management

strategies using crop rotation, and potential usage of fungicides.

42

Alternative management strategies to control fungicide‐resistant

Phytophthora erythroseptica populations in Canada.

RD Peters1*, Crane, B1, LM Kawchuk2, KI Al-Mughrabi3, A MacPhail1,

KA Drake1, D Gregory1, and M. Trenholm11.

1AAFC, PE; 2AAFC, AB; 3NBDAAF, NB.

Management of pink rot, caused by Phytophthora erythroseptica, has relied upon

application of metalaxyl-m (Ridomil Gold ®), either at planting or as a foliar spray during

the growing season in Canada. National surveys to assess the distribution of metalaxyl-

m resistant strains of P. erythroseptica were conducted in 2013 and 2014. Samples of

infected tubers were used to obtain isolates of the pathogen for subsequent testing for

metalaxyl-m sensitivity using an amended agar assay. Isolates of P. erythroseptica with

resistance to metalaxyl-m were recovered from PE, NS, NB, ON, MB and AB. Most

isolates with resistance to metalaxyl-m were recovered from eastern Canada. A

replicated, inoculated field trial was established in PE to assess the efficacy of products

applied in-furrow against metalaxyl-m sensitive and resistant strains of P.

erythroseptica. Incidence of pink rot in harvested daughter tubers was used as a

measure of product efficacy. Up to 30% of tubers in inoculated control plots were found

with pink rot at harvest. As expected, Ridomil Gold ® was able to suppress disease

caused by metalaxyl-m sensitive strains, but not by metalaxyl-m resistant strains.

PhostrolTM was able to significantly suppress pink rot caused by both pathogen strains,

when applied as multiple foliar sprays during the growing season, but not when applied

in-furrow at planting. PresidioTM and oxathiapiprolin were also successful at preventing

pink rot caused by either pathogen strain, but Serenade® was not efficacious against

either strain under the parameters of the field trial. Although resistance to metalaxyl-m is

becoming more widespread in Canada, some alternatives for disease control are now

available to growers and others should be forthcoming in the near future.

43

Bacterial antagonists as a biological solution for control of potato late blight.

Patrice Audy2*,Nicholas Foran1, Susan M. Boyetchko3 and Valerie Gravel1.

1Dept. of Plant Science, Macdonald Campus, McGill University, Ste-Anne-De-Bellevue,

QC H9X 3V9, Canada; 2Agriculture and Agri-Food Canada, Quebec Research and

Development Centre, Quebec, QC, G1V 2J3, Canada; 3Agriculture and Agri-Food

Canada, Saskatoon Research and Development Centre, Saskatoon, SK, S7N 0X2,

Canada.

Late blight, caused by the oomycete Phytophthora infestans (Mont.) De Bary, is the

most devastating disease affecting the potato, accounting for over six billion US dollars

worldwide each year due to production losses and prevention measures. For many

years, synthetic fungicides have been used heavily by potato producers to minimize

disease severity and prevent spread. But the incidence of new, more virulent P.

infestans genotypes – many of which now fungicide-resistant – has made it increasingly

difficult and costly for producers to prevent late blight epidemics. The use of biological

fungicides has thus been of considerable interest among plant pathologists in recent

years for their ability to produce powerful antifungal compounds and to induce systemic

resistance in host plants. A detached fed-leaf bioassay was used to test the

effectiveness of six potential bacterial biocontrol agents against four P. infestans

isolates. Data analysis revealed that the level of biocontrol differed greatly among the

six bacterial strains; the 189 isolate being significantly different than the control (P ≤

0.05) for 28 of the 32 measurements while this was true for the OY3WO11 isolate only

once. Time-delay experiments were also conducted using the top two candidates, 189

and WAUSV36, in order to determine if differences in biocontrol existed when the time

between treatments and infection was increased. A significantly reduced biocontrol

efficacy was detected when bacterial treatments were applied 24 hours before infection

(compared to 2 and 18 hours) from measurements taken after seven days only.

Integrating the use of bacterial antagonists into late blight management strategies can

prove to be an effective addition to current prevention methods and help curb the heavy

use of synthetic fungicides in potato production.

44

The Use of Bacillus bacteria Applied In-Furrow to Reduce Common

Scab on Potatoes

Robert Coffin1*, Joyce Coffin1, Steve Watts2, Claudia Goyer3 and Catherine Clark3

Privar Farm Inc., 909 Eliot River Road, N. Wiltshire, PEI, C0A 1Y0, 2. Genesis Crop

Systems Inc., Crapaud, PEI, C0A 1J0, 3. Agriculture and Agri-food Canada,

Fredericton, N.B., E3B 4Z7

Background

Common Scab is recognized world-wide as a serious disease of potatoes. It has caused

extensive financial losses for growers. The lesions and cavities on the tubers can make

potato tubers non-marketable for seed, table and processing markets. Common scab is

caused by several species of Streptomyces bacteria. These bacteria can live and

multiply on organic matter in the soil. In addition to colonizing potato tubers, they can

grow on any crop with a tap root including beets, radishes and carrots. Species of

Streptomyces that cause scab lesions produce toxins called thaxtomins. Thaxtomins

inhibits cellulose synthesis in cells of potato tubers.

A wide range of control measures have been evaluated by researchers and farmers,

and most have been inconsistent and/or inadequate. An excellent review on common

scab, with numerous references, was published by Dees and Wanner (2012). No

commercial varieties of potatoes are immune to scab. It is recognized that some

varieties of potatoes have much better tolerance to common scab infection than others,

but the actual mechanisms of common scab resistance are poorly understood. Due to

the presence of different biotypes/ species of Streptomyces, the susceptibility of potato

varieties to common scab symptoms can vary with location. St-Onge et al. (2008)

conducted a survey of potato scab samples from the Maritime Provinces. Genome

fingerprinting of Streptomyces with PCR revealed 10 distinct genetic groups. Some

success in suppression of common scab symptoms has been obtained with chemical

control (chloropicrin fumigation). However, fumigation is not permitted in some potato

production areas (PEI).

There is increasing interest in evaluating naturally occurring bacteria as biological

pesticides (bio-pesticides). Some species of Streptomyces can suppress the

development of scab (scab suppressive strains). Some success occurred when potato

45

seed pieces were inoculated with species of Bacillus and/or Pseudomonas bacteria

leading to a reduction in the number and severity of scab lesions on daughter potato

tubers (Basahi, FZB24 internet report, Goyer, Al-Mughrabi). Compost tea has provided

some control of common scab but variations can occur among different batches of

compost and compost tea.

Using tolerant varieties is one of the best approaches to reduce damages caused by

common scab. Somaclonal variation is an encouraging approach to create more

tolerance to common scab using existing varieties. In Australia, Wilson et al (2009)

were able to select for common scab tolerant selections of commercial potato varieties

by regenerating plantlets from potato cells exposed to thaxtomin in growth medium

These plants were shown to be more resistant to common scab and other soil-borne

diseases under field conditions. Somaclonal variants more resistant to thaxtomin were

made from calli adapted to increasing amount of thaxtomin in research programs in

Quebec (Beaudoin et al , 2012) and New Brunswick (Goyer, unpublished).

Current study and findings

This research project was conducted at Privar Farm Inc., Green Bay, PEI in 2015. The

land had been farmed in the 1800s, reverted back to spruce forest and was re-cleared

10 years ago . Many varieties/seedlings of potatoes developed extensive common scab

in the soil regardless of soil pH. The soil pH of the newly cleared land was 4.7.

Additions of lime to raise the pH to 7.0 did not alter the severity of common scab. Over

the past 10 years, many options were attempted to reduce common scab. Several

options showed promise for commercial scale use (Table 1).

Table 1 Efforts to control common scab on PEI

NO EFFECT SOME PROGRESS IN SCAB

SUPPRESSION

Green clay Oxytetracycline in furrow

Crop rotations with oats, rye, clover,

Timothy, oilseed radish, buckwheat

Extract from horse radish (isothiocyanates)

In furrow

Lime (Calcitic, Dolomitic)

Privar Farm Inc. potato breeding program –

selection of scab resistant seedlings

Sulfur fertilizers (pure sulfur, ammonium Endophytic fungus that colonized potato

46

sulfate) tissues

Serenade Soil (Bacillus subtilis bacteria)

Bayer product

2015 Microflora Pro TM containing Bacillus

subtilis and Bacillus amyloliquefaciens

bacteria

In the spring of 2015, an investigative trial was initiated to verify the efficacy of

Microflora Pro TM. It is sold as plant growth promoting rhizobacteria, registered in

Canada #2014017A, Fertilizer Act by Abnatura Company, Quebec. No claims are

made on the current product label regarding control of common scab. This product

contains Bacillus subtilis and Bacillus amyloliqueifaciens. Evaluations in Europe with

Bacillus preparations, such as FZB24, have reduced common scab on tubers of a

number of potato varieties.

Application of Microflora Pro – A furrow was opened and seed pieces of 5 potato

varieties/seedlings were placed in the open furrow. Twenty-four mls of Microflora Pro

was mixed with 1 litre of water and applied with a watering can (20-25 cm swath) to a 20

meter section of the open furrow. The furrow was covered immediately after application.

Previous crops in this field had been oats (2014) and oilseed radish (2013). Several soil

tests indicted the pH ranged from 6.0-6.5 and organic matter from 3-4%.Tuber samples

were harvested several times in September and rated for scab (Table 2).

Table 2. Observations on common scab control, September, 2015

Variety/seedling Treated (Microflora Pro) Non-treated

Red Pontiac Clean bright skin, negligible

lesions

Numerous large lesions and pits

Shepody 20-25 % of skin with surface scab 75% of skin with surface scab

Prospect Clean skin with slight pits Some surface scab and pits

Privar Blue seedling No scab, bright skin Negligible lesions but dull skin

Privar white seedling Negligible scab, bright skin Slight surface scab, dull skin

We observed almost complete control of scab lesions in Red Pontiac; whereas, most

Red Pontiac tubers in the non- treated row were severely damaged by scab and were

not usable (figure 1). Partial control of scab occurred in Shepody and Prospect. The two

seedlings (Privar blue and white) with resistance to scab had much brighter skin in the

47

treated section of row (figure 2).No phytotoxic effects on any treated potatoes plants

were observed in the Microflora Pro treatment.

Red Pontiac Treated (right), non-treated (left) Privar blue, Treated (right), non-treated (left)

Figure 1. Photo of treated (Microflora Pro) and non treated potato samples

Planned future studies and challenges

Biopesticides usually contain living organisms and/or metabolites from organisms. In

comparison to synthetic chemical pesticides that can be stored for years before use,

special storage regimes may be required to assure activity of biological pesticides.

Methods need to be developed to verify if cultures are alive and determine the most

effective way to apply the product, such as treating seed pieces or application in-furrow.

Microflora Pro will be evaluated on different potato varieties using different application

techniques.

Future plans include assessments of the efficacy of different strains/species of Bacillus

and Pseudomonas bacteria. A project, similar to the one reported by Wilson et al , 2009

and Beaudoin et al, 2012 may be initiated with the aim of detecting somaclonal variants

with improved scab resistance in commercial potato varieties.

For an effective program to reduce scab with bio-pesticides, several steps may be

necessary:

1. Determine the species of Streptomyces bacteria in the soil that are responsible for

common scab on a field to field basis. Investigate current PCR probe (St-Onge et al

2008) for detection and quantification of pathogenic Streptomyces bacteria and develop

suitable sampling strategy and methods to measure pathogenic Streptomyces spp in

commercial fields.

48

2. Document the strains/species of beneficial bacteria that can suppress common scab

development in a given location.

3. Assess which potato varieties respond favourably to specific bacterial treatments.

A question that has been asked is would be possible to develop a soil test that could be

used to assess the risk of common scab in a field before planting the field. This would

permit management decisions to be made regarding the planting of potatoes. If the risk

was high, the grower might decide not to plant the field to potatoes or make a decision

to plant a variety with documented resistance to scab. Also, this might permit the

effective use of specific bacteria to suppress scab. Investigations may be initiated to

assess current PCR probes and develop suitable sampling strategy to adequately

measure pathogenic Streptomyces spp in commercial fields to assess soil samples to

document the type and amount of inoculum that is present.

During the summer of 2015, Microflora Pro was evaluated in field scale trials by S.

Watts. Some indications of increased yield and decreased common scab were

documented. Further research is planned to evaluate the best method of application

and to verify product efficacy on different potato varieties grown under different

conditions.

References (all are accessible on Internet) Al-Mughrabi K. et al, 2016 Management of common scab in the field using bio-pesticides, fungicides, soil additives and soil

fumigants. Biocontrol Science and Technology 26(1) 125-135

Al-Mughrabi K. I., Berthelene C., Livingston T., Burgoyne A., Poirier R., and Vikram A, 2008. Aerobic compost tea, compost

and a combination of both reduce severity of common scab (Streptomyces scabies) on potato tubers. Journal of Plant Sciences 3

(2) 168 – 175.

Basahi, Muna. 2014 M.Sc. thesis. Seed tuber treatments with Pseudomonas spp. to reduce potato common scab incidence and

severity. Electronic Thesis and Dissertation Repository. Paper 2171, http://ir.lib.uwo.ca/etd/2171.

Beaudoin, N. et al., 2014 Increased resistance to common scab in potato lines regenerated from thaxtomin A –adapted cells.

American J. Potato Research 91, page 36.

Bio-pesticides http://www.agr.gc.ca/eng/news/science-of-agricultural-innovation/agriculture-and-agri-food-canada-scientists-

looking-to-nature-to-control-the-disease-that-caused-the-irish-potato-famine/?id=1433168638577

Dees M. W. and Wanner L., 2012, In search of better management of potato common scab. Potato Research 55 p 249-268.

Goyer et al, 2011, Strategy to deliver Bacillus strains in the field to control common scab. Proceedings of North East Potato

Technology Forum.

Michigan Potato diseases – common scab of potato fact sheet, Phillip Wharton et al, www.potatodiseases.org/scab.html

Roquigny R., Arsenault T., Gadkar V., Novinscak A., Joly D., and Filion M. 2015 Complete Genome Sequence of Biocontrol

strain Pseudomonas florences LBUM223. Genome Announc. 3 (3).

St -Onge R., Goyer C., Coffin R., Filion M., 2008 Genetic diversity of Streptomyces spp. causing common scab in eastern

Canada. Syst. Appl. Microbiol. 31(6-8) p 474-484.

Wale S. and M. Sutton, 2005. Research review- Supplement to the literature review on non-water control measures for potato

common scab. Ref: R248. British Potato Council on line, 31 pages

Wilson ,C. et al. , 2009, “Enhanced resistance to common scab through somatic cell selection in cv. Iwa with the phytotoxin

thaxtomin A. Plant Pathology Journal, vol. 58 #1, pages 137-144.

49

Management options to reduce wireworm damage in potatoes

Christine Noronha*, Natasha Boyle and David Carragher

Charlottetown Research and Development Centre, Charlottetown, PE.

Wireworms have been identified as important pest and can cause significant economic

damage to potatoes and other field crops. The adults, also known as click beetles,

emerge in early spring and each female will lay 100-200 eggs in the soil. The eggs

hatch into wireworms that live for five years underground where they feed on roots and

tissues of plants before becoming adults. Populations tend to build up in sod and

pasture fields and buffer zones from where they move into crop fields to lay eggs thus,

causing crop damage. Until now the only way to trap adults was to use pheromone

traps. However, pheromones are species specific, they only trap male click beetles and

are used as a monitoring tool. Because pheromones do not trap females, they cannot

be used to reduce populations. We have developed a new light trap (NELTTM) that will

capture both male and females beetles in large numbers. In 2015, the efficacy of the

traps was examined in two heavily infested fields in PEI. We found significantly higher

numbers of beetles in our light traps (900 beetles /trap) as compared to the traps

without lights (300 beetles /trap). Both male and females beetles were collected in high

numbers. In addition beetles of three different species were collected indicating that this

trap is not species specific. The trap is very user friendly and can be easily installed

within crop fields, buffer zones and pasture fields. Mass trapping, using this trap has

the potential to reduce populations by removing females in large numbers before egg

lying begins. Details of the trap will be discussed.

50

Metabolomics of Colorado potato beetle resistance in

S. oplocense X S. tuberosum hybrids

Helen H. Tai1*, David de Koeyer1, Kraig Worrall1, Yvan Pelletier1 and Larry Calhoun2

1Agriculture and Agri-Food Canada Potato Research Centre, P. O. Box 20280, 850

Lincoln Rd., Fredericton, New Brunswick, Canada, E3B 4Z7; 2Department of Chemistry,

University of New Brunswick, P.O. Box 4400, Fredericton, New Brunswick, Canada,

E3B 5A3

Canada

The Colorado Potato Beetle Leptinotarsa decemlineata (Say) (CPB) is a coleopteran

herbivore that feeds on the foliage on Solanum species, in particular, potato. Six

resistant wild Solanum species were identified and two of these species had low levels

of glycoalkaloids. Comparative analysis of the untargeted metabolite profiles of the

foliage using liquid chromatography-mass spectrometry (LC-MS) was done to find

metabolites shared between the wild species but not Solanum tuberosum (L.) to identify

resistance-related metabolites. It was found that only S. tuberosum produced the triose

glycoalkaloids Solanine and Chaconine. Instead, the six wild species produced

glycoalkaloids that shared in common tetraose sugar side chains. The most common

among the tetraose glycoalkaloids was dehydrocommersonine. One of the wild species

S. oplocense Hawkes, was intercrossed with S. tuberosum. Backcross clones carried

varying levels of resistance. Differences in foliar metabolites between resistant and

susceptible clones were analyzed using LC-MS. Supervised machine learning

classification methods were applied to develop algorithms that can classify resistant and

susceptible plants using the metabolite data. Resistance was associated with a

change in composition of glycoalkaloids to higher ratios of dehydrocommersonine over

solanine.

51

Session E:

Session Chair: Gefu Wang-Pruski, Dalhousie University, Truro, NS

Thursday, March 17, 2016

1:30 pm - 3:00 pm

52

Reduced Steroidal Glycoalkaloid Levels Affects Solanum tuberosum resistance

against Pests and Diseases

Jamuna Risal Paudel1*, Charlotte Davidson1, Leslie Campbell2, Cathy Clark1, Lana

Nolan1, Jun Song2, Agnes Murphy1, Maxim Itkin3, Asaph Aharoni4 and Helen H. Tai1

1 Agriculture and AgriFood Canada, Potato Research Centre, Fredericton, NB, Canada

2Agriculture and AgriFood Canada, Atlantic Food and Horticulture Research Centre,

Kentville, NS, Canada

3Department of Vegetable Research, ARO-Volcani Center, Bet Dagan, Isreal

4 Department of Plant Sciences, Weizmann Institute of Science, Rehovot, Isreal

Steroidal glycoalkaloids (SGAs) are toxic to humans at high levels, but their role in plant

protection against pests and pathogens is less clear and is investigated here. Solanine

and chaconine are the major SGAs in cultivated potato, Solanum tuberosum. Levels of

SGAs can be manipulated by modifying genes encoding enzymes in the SGA

biosynthesis pathway. For this study, we generated S. tuberosum cv. Bintje lines with

reduced levels of solanine and chaconine by knocking down Glycoalkaloid Metabolism 4

(GAME4) gene, which encodes a cytochrome P450 enzyme involved in an oxidation

step in the conversion of cholesterol to SGAs. We examined the survival and

development of Colorado Potato Beetle (CPB), a notorious pest of cultivated potato, on

the wild type and GAME4 knockdown lines. Although many larvae died at earlier stage

(L1-L3) in GAME4 knockdown lines, development from larval to adult stage was faster

in these lines than wildtype plants. We also studied the biotic resistance of S.

tuberosum against Phytopthora infestans and Verticillium dahliae under this altered

metabolic profile. Pathogen infection studies showed that the GAME4 mutants had

increased resistance against Phytophthora, whereas they were more susceptible to

Verticillium.

53

The Effects of Low Levels of CIPC on Seed Potato Performance

John Walsh, Associate Principal Scientist, Potato Storage McCain Foods Limited

Thirty years ago, most potato growers in Maine, New Brunswick and PEI grew a small

amount of seed to use on their farms. They always had one seed storage for both

holding and cutting the seed prior to planting. As growers became more specialized,

many converted their seed storages to processing or table storages and began using

CIPC to control sprouting. Unfortunately, that left many without a specialized, CIPC-

free, building where they could cut their seed. Instead, they would clean and disinfect

the CIPC-treated storage before moving seed in for cutting, curing and holding the seed

prior to planting. This practice has alarmed many local agronomists but, without any

proof, it has been difficult to discourage the practice.

Last year we conducted a small trial where we evaluated three storages that were, or

could be, used to cut seed; 1) A control storage where no CIPC was used (Wicklow); 2)

a “Clean” storage that was used to hold CIPC-treated potatoes that year but was

cleaned and disinfected prior to delivery of any seed; and 3) A “Dirty” storage where

CIPC had been used and CIPC-treated potatoes were still in the back of the bin. We got

two surprised. One was that the CIPC-free storage had detectable residues of CIPC.

We later determined that samples of CIPC-treated potatoes had been held there and

were enough to contaminate the storage. We also found that the so-called “Clean”

storage had the highest residues. It was eventually discovered that a chip-stock

storage, directly across from where the seed samples were stored, had been treated

with CIPC as recently is mid-March (6 weeks before the samples arrived) and was not

completely sealed so that CIPC contaminated air reached the samples. The samples

from this storage had residues in the range of 0.080 to 0.105 ppm, which caused slower

emergence and a statistically significant yield reduction of more than 8%.

This year we decided to dip seed potatoes in known concentrations of CIPC to expose

the seed to a range of CIPC levels: 0, 0.025, 0.050, 0.1, 0.2 and 0.4 ppm. Residue tests

on the seed showed that while we were relatively close to the three lowest intended

levels, we were low on the higher rates. Actual CIPC concentrations were 0, 0.021,

0.033, 0.043, 0.065 and 0.135 ppm for Russet Burbank, and 0, 0.022, 0.039, 0.070,

54

0.120 and 0.188 for Innovator. As before, emergence was delayed by CIPC, with higher

rates emerging more slowly. There was also a statistically significant effect on total yield

in Russet Burbank, with rates above 0.050 (intended) having progressively lower yields,

and the highest rate reducing yield almost 10%, a statistically significant effect. We had

to discard the Innovator results due to a problem in the harvested samples. Samples of

grower storages used to cut seed revealed tuber residues ranging from 0 to 0.200 ppm.

There was evidence that rates were highest above the ventilation ducts. Unfortunately,

we didn’t have an opportunity to follow those samples into the field.

55

Uncovering associations between the genomic segments and selection

parameters with disease resistance and agronomic and quality traits

in cultivated potato

Jiazheng Yuan1, Agnes Murphy1, David De Koeyer1, Umesh Rosyara2, Martin Lague1,

and Benoit Bizimungu1

1 Potato Research Centre, Agriculture and Agri-Food Canada, Fredericton, New

Brunswick, Canada, E3B 4Z7. 2 Dept. Horticulture, Univ. Wisconsin, Madison, WI

53706, USA. 1 Corresponding Author (Benoit.Bizimungu@agr.gc.ca).

Cultivated potato (Solanum tuberosum) is the fourth most important food crop in the

world. Potato clones are selected from the F1 progenies via vegetative propagation

without further genetic modification. Thus potato breeding efforts rely heavily on

phenotypic selection to improve yield and other traits of interest. Furthermore, the allele

dosage of tetraploid potato can affect the level of gene expression and may result in

phenotypic differences. Therefore breeders are often faced with the challenge to identify

the associations between molecular markers and target traits in potato.

In this study, a set of advanced breeding lines of tetraploid cultivar and three bulked

DNAs with opposite phenotypes of disease resistances were genotyped using Illumina

12 K Infinium HD chips in GeneSeek, a Neogen company. This allowed us to analyze

the association between the genomic segments of potato lines and the target traits

using the GWASpoly platform, a R package for Genome-wide association studies

(GWAS) on polyploid potato. Using data from evaluation trials over three years at the

Benton Ridge breeding substation in Atlantic Canada, we also deciphered the dynamic

properties of trait expression over the growth period based on nine selection parameters

used in the Agriculture and Agri-Food Canada’s potato breeding program. By using

linear mixed model fit by maximum likelihood and principal component analysis (PCA),

we analyzed the phenotype data to extract information on useful phenotypic characters

for potato yield breeding. The analysis of breeding data provided valuable information to

understand the factors that contribute to the phenotypic performance of potato and

potato tuber yield and culinary traits. Information generated allows us to better

understand the associations between the molecular markers and genetic composition of

56

the advanced breeding lines in order to apply the marker-assisted selection in potato

selection.

57

Identification of Chromosomal Locations in Potatoes Associated with

Tuberization Traits Affected by Photoperiod Using SNP Markers

Maria Caraza1*, David De Koeyer3, Elisa Mihovilovich2, Merideth Bonierbale2, Gefu

Wang-Pruski1

1 Dalhousie University – Faculty of Agriculture, Truro, NS, Canada; 2 International

Potato Center, Lima, Peru; 3 Agriculture and Agri-Food Canada - Potato Research

Centre, Fredericton, NB, Canada; 3 International Institute of Tropical Agriculture,

Ibadan, Nigeria

Understanding tuberization traits is critical for developing potato varieties that are

broadly adapted to diverse and changing environmental conditions. Since tuberization

traits in potatoes are affected by photoperiod, this study is aimed at identifying markers

on chromosomes that are associated with tuberization related traits. We evaluated 171

tetraploid breeding lines developed by the International Potato Center breeding

program. Their tuberization related traits were evaluated under short (12 hours) and

long (16 hours) photoperiod exposures, measured at 75 and 90 days after planting.

Clones were genotyped with the Potato SolCAP SNP array; and 4,738 informative

SNPs were used for subsequent analyses. Marker and trait data were used to study the

population structure, linkage disequilibrium, and to identify associations between SNPs

and the tuberization related traits. There were significant variations in maturity and

photoperiod-response genes in the germplasm studied. Most significant SNPs detected

were identified on the same regions as previously reported genes affecting photoperiod

related traits; and several of these SNPs were clustered within small genomic regions.

Genome wide association analysis identified novel functional variations that can be

used in variety development through marker assisted selection.

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Biological predictors for tuber sweetening during long term cold storage.

Jonathan Neilson1, Martin Lagüe1, Susan Thompson3, Frédérique Aurousseau2, Agnes

Murphy1, Benoit Bizimungu1, Virginie Deveaux2, Yves Begue2, Jeanne Jacobs3 and

Helen H. Tai1

1 Agriculture and Agri-Food Canada Potato Research Centre, P. O. Box 20280, 850

Lincoln Rd., Fredericton, N. B., Canada E3B 4Z7; 2 Sipre-Responsable Scientifique

Creation Varietale, Station de Recherche du Comite Nord, 76110 Brettevukke du Grand

Caux, France ; 3The New Zealand Institute for Plant and Food Research Limited,

Private Bag 4704, Christchurch, New Zealand

Cold temperature (4 degrees Celsius) is routinely used in potato agriculture to prevent

budding during storage. However, this leads to a phenomenon known as cold-

sweetening where sugars accumulate in tuber tissue. The presence of reducing sugars

in tuber tissue during frying results in an undesirable browning and production of toxic

substances, such as acrylamide. Potato varieties exhibit different levels of cold-

sweetening, suggesting an underlying genetic mechanism controlling sugar

accumulation during cold storage. To untangle the mechanism behind cold-sweetening

we measured glucose concentration and sequenced the transcriptomes of 10 different

potato varieties that show different levels of glucose accumulation before and 3 months

after cold storage. Many of the genes that exhibit a transcriptome expression profile

similar to differences observed in glucose levels appear to be involved in regulating the

response to cold stress as well as desiccation stress. This suggests that pathways

regulating the response to cold are shared with water loss and that post-translational

regulation is involved in control of cold-sweetening. From this data we have identified a

candidate list of genes that may be used as biomarkers to predict the magnitude and

kinetics of cold-sweetening over the storage period. We are currently in the process of

validating these genes as a test to be used by growers during long term, cold storage to

make better informed crop management decisions and by plant breeders as markers for

susceptibility to cold-sweetening.

59

Sweet potato clonal differences in organic trial performance, dry matter content,

starch content, and starch granule characteristics in New Brunswick

Xiu-Qing Li 1*, Suyan Niu (1,2), Ruimin Tang (1,3), Fanrui Meng (4), Guoqiang Fan (2),

Qing Yang (3), Loretta Mikitzel (5), and Muhammad Haroon (1)

(1) Fredericton Research and Development Centre, Agriculture and Agri-Food Canada,

850 Lincoln Road, Fredericton, NB, E3B 4Z7, Canada. ; (2) Paulownia Research

Institute, Henan Agricultural University, 95 Wenhua Road, Jinshui District, Zhengzhou,

Henan, P.R. China. (3) Department of Biochemistry and Molecular Biology, College of

Life Sciences, Nanjing Agricultural University, Nanjing, 210095, P.R. China

(4) Faculty of Forestry and Environmental Management, University of New Brunswick,

Fredericton, New Brunswick, E3B 6C2, Canada. ; (5) Potato Development Centre, New

Brunswick Department of Agriculture, Aquaculture & Fisheries 39 Barker Lane Wicklow

NB Canada E7L 3S4, Canada

Sweet potato (Ipomoea batatas) is a crop of increasing importance in Canada. Both

sweet potato fries and fresh sweet potatoes, particularly organically grown sweet

potatoes, are popular to consumers in the Atlantic region. Dry matter content and starch

properties can greatly influence the quality of fries and the suitability for certain cooking

methods. However, there is very little research on sweet potato cultivar performance

and starch granule characteristics in Canada. We conducted organic trials with several

sweet potato clones (three white flesh, four yellow flesh, and two purple flesh) in 2014

and 2015 at the experimental farm of the Fredericton Research and Development

Centre (Agriculture and Agri-Food Canada) in Fredericton, New Brunswick. The

purpose of this study is to investigate the following: 1) whether there is a difference in

the yield per hill between the two most popular cultivars—“Beauregard” and “Covington”

in New Brunswick; 2) whether there is a negative or positive correlation between the

vine fresh yield and the storage root fresh yield; 3) how dry matter content correlates

60

with starch content; 4) what the differences are in starch characteristics between white

fleshed, purple fleshed and yellow fleshed cultivars; 5) whether the starch granule size

is correlated with starch content, dry matter content and flesh color. The potential use of

starch granule characteristics as non-molecular markers for processing quality traits of

sweet potatoes will be discussed.

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NOTES

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NOTES