For Review Only - University of Toronto T-Space · For Review Only 1 Organic selection may improve yield efficiency in spring wheat: A preliminary analysis. Laura Wiebe 1, Stephen

For Review O

nly

Organic selection may improve yield efficiency in spring

wheat: A preliminary analysis.

Journal: Canadian Journal of Plant Science

Manuscript ID CJPS-2016-0141.R2

Manuscript Type: Article

Date Submitted by the Author: 11-Oct-2016

Complete List of Authors: Wiebe, Laura; Plant Science Fox, S.; DL Seeds, Entz, Martin; University of Manitoba, Plant Science

Keywords: Plant physiology, Protein, Nitrogen, Organic

https://mc.manuscriptcentral.com/cjps-pubs

Canadian Journal of Plant Science

For Review O

nly

1

Organic selection may improve yield efficiency in spring wheat: A preliminary analysis.

Laura Wiebe1, Stephen L. Fox

2 and Martin H. Entz

1

1Department of Plant Science, University of Manitoba, Winnipeg, MB, R3T 2N2

2DL Seeds Inc. Mailing address: PO Box 1123, La Salle, MB, R0G 1B0

Corresponding Author: M. H. Entz

Keywords: Plant physiology, protein, organic, nitrogen

Organic spring wheat (Triticum aestivum) breeding programs have been initiated, yet

yield efficiency and N economy research is limited. We evaluated the performance of

advanced lines selected from an organic breeding program initiated in 2003. Fourteen F8 and

F9 lines in 2009 and 11 lines in 2010 were compared with commercial (check) cultivars. Field

experiments were conducted under organic management at four site-years in Manitoba and

Saskatchewan. Combined analysis showed no difference in biomass accumulation between

organic lines and check cultivars; however, harvest index (HI) and grain yield were greater in

organic lines compared with the checks. Organic lines were shorter than check cultivars, but

yield efficiency, defined as kernel number per unit of crop biomass at anthesis (KNO:DMa)

was higher (P<0.05). Kernel mass was also greater for organic lines. Biomass N uptake was

similar for organic lines and check cultivars though total uptake of N into grain was greater

for organic lines. Average grain protein content of organic lines was significantly lower than

for check cultivars. This study demonstrated that improved yield under organic management

was due to better assimilate partitioning, both at anthesis and crop maturity, for organically

selected genotypes.

Page 1 of 25



For Review O

nly

2

INTRODUCTION

The crop grown on the most organic acreage across the Canadian Prairie is spring

wheat (Triticum aestivum) (Macey 2010). However, wheat cultivar choices are limited

mostly to conventionally-bred types. While one wheat cultivar was recently developed

exclusively under organic selection and is now registered in Canada (eg. AAC Tradition), it

is not yet in large-scale commercial production.

Research in North America and Europe has focused on adaptation of commercial

wheat cultivars to organic production in an effort to identify suitable cultivars and to better

understand traits important in organic production. Carr et al. (2006) observed that some

modern cultivars ranked consistently high for yield, protein content, and volume weight when

grown under organic management. Mason et al. (2007) identified crop height and early

maturity as the traits most closely associated with positive performance of conventional

wheat cultivars under weedy conditions in Alberta. Lammerts van Bueren et al. (2011)

identified the ability to assimilate macronutrients during the growing season as important for

cultivar performance under organic management, though Nelson et al. (2011) observed no

difference in mycorrhizal colonization of five wheat cultivars in organic fields. Fernandez et

al. (2014) identified resistance to leaf spotting diseases as important for performance of

wheat grown under organic management in Saskatchewan.

Several studies have compared modern and older ”heritage” wheat cultivars in an

attempt to identify positive traits among the older genotypes. Murphy et al. (2008) found

that older cultivars contained higher levels of micronutrients, while Pridham et al. (2007)

found no difference in yield performance between Red Fife, a tall 1890’s cultivar, and two

shorter modern wheat cultivars under organic production. Martens et al. (2014) found that

Page 2 of 25



For Review O

nly

3

older cultivars, including Red Fife, were generally lower yielding and more leaf rust

(Puccinia spp.) susceptible than modern cultivars; this difference was greatest under heavier

leaf rust. Kirk et al. (2011) observed that older cultivars, including Red Fife, had lower

mycorrhizal colonization and grain yield than modern cultivars when grown organically;

however, no tissue P concentration differences were observed.

The interest in cultivar adaptation to organic production has spurred interest in

dedicated organic breeding programs (Lammerts van Bueren et al. 2002). In their study of 35

different soft white winter wheat breeding lines, Murphy et al. (2007) found that direct selection

within organic systems resulted in yields 5 to 31% higher than indirect selection in conventional

systems. Others have reported similar results (Reid et al. 2009; Kirk et al. 2012), though

Kronberga et al. (2013) found no advantage to direct selection in triticale (Triticale ×

Triticosecale).

Major challenges of organic farming include nutrient and weed management (Entz et

al. 2001). So it is not surprising that organic wheat breeding programs have focussed on

improved nutrient use efficiency (Dawson et al. 2008) and weed competitiveness (Mason et

al. 2008b). Organic breeding lines have also been evaluated for grain quality, predominately

protein content (Wang et al. 2003). Mason et al. (2007) reported that cultivars grown under

organic management tended to have higher dough strength and comparable grain protein

levels compared with the same cultivars grown under conventional management. Nelson et

al. (2011) found higher protein levels in organic systems, but this was due to lower yield; ie.,

protein concentration. Kirk et al. (2012) observed that both grain yield and protein content

were higher in organically-selected spring wheat populations.

Harvest index (HI) is a common measure of yield physiology, but Doyle and Fischer

(1979) proposed additional indices that provide a deeper understanding of crop physiological

responses to the growing environment. These include kernel number per unit area of land,

Page 3 of 25



For Review O

nly

4

kernel number per unit of biomass at anthesis (called the kernel production efficiency) and

grain yield per unit of biomass at anthesis (Fisher and Kohn 1966; Doyle and Fisher 1979).

Kernel production (ie., kernels per unit area of land and per unit of biomass) is an important

measure in a sink limited crop such as wheat (Entz and Fowler 1990; Fisher and Edmeades

2010). No previous studies have considered yield physiology of organic vs. conventionally

developed wheat genotypes.

The present study examined advanced breeding lines (F8 in 2009 and F9 in 2010) from

the Agriculture and Agri-Food Canada/University of Manitoba spring wheat organic breeding

program. Breeding lines for inclusion in the present study were selected on the basis of yield

performance and high protein content in preliminary organic yield tests where grain had been

screened for protein in the F4 generation. These breeding lines were compared with

conventional check cultivars. We hypothesized that the organically-selected lines would

have improved yield efficiency and greater N uptake than check cultivars when grown under

organic conditions. Varietal adaptation to organic farming has often been addressed by

comparing the same set of lines in organic and conventional environments (Murphy et al.

2007). The present study, instead, compared organically selected lines with a set of

conventional commercial cultivars, all grown in an organic environment.

MATERIALS AND METHODS

Site Description

Field experiments were conducted over four site-years, two in 2009 and two in 2010.

In 2009 experiments were located at University of Manitoba’s Research station in Glenlea,

Manitoba (49.6° N, 97.1° W; Red River clay; Gleyed Humic Vertisol, Canadian System of

Soil Classification 3rd ed. , 1998) and on an organic farm near Oxbow, Saskatchewan (49.2°

N, 102.1° W; Oxbow clay loam; Orthic Black Chernozem, Canadian System of Soil

Page 4 of 25



For Review O

nly

5

Classification 3rd ed. 1998). In 2010 experiments were established at the University of

Manitoba’s Ian N. Morrison research farm in Carman, Manitoba (49.5° N, 98.0° W; Hibsin

fine sandy loam; Orthic Black Chernozem, Canadian System of Soil Classification 3rd ed.

1998), and the same organic farm at Oxbow. The sites were selected to represent a range of

organic cropping systems in three different regions of the eastern Canadian Prairies.

Soil samples were collected at each site prior to or just shortly after seeding from

three depths (0-15cm, 15-60 cm, 60-120 cm) and were sent to Agvise laboratories in

Norwood, North Dakota for analysis (Table 1). Weather data collected by Manitoba

Agriculture, Food and Rural Initiatives (MAFRI 2011), Environment Canada’s climate data

online (Environment Canada 2011a), and weather normals (Environment Canada 2011b) are

presented in Tables 2 and 3. Data for 30-year normals site based on values from Graysville

weather station (approximately 14 km from Carman site). Weather data for Glenlea 2009 was

taken from the Winnipeg weather station (approximately 32 km from Glenlea site). The

weather data for the Oxbow site was from the Estevan weather station (approximately 65 km

from Oxbow site).

Experimental Design and Treatments

A total of 14 F8 and F9 lines were examined in 2009 and 11 lines in 2010 were grown

in addition to commercial Canadian Western Red Spring Wheat (CWRS) cultivars.

Advanced breeding lines were sourced from the Agriculture and Agri-Food Canada/

University of Manitoba organic spring wheat organic breeding program. The original crosses

were made in 2003 and grown in organically-managed nurseries at Carman, Manitoba. The

nursery contained a low level of weeds (approximately 1500 kg ha-1

weed biomass at wheat

harvest). Nitrogen was supplied to crops from a pea/oat green manure grown the previous

year. Pedigree of the cross was between two breeding lines, 98B25-AS6DOI and ND744U

Page 5 of 25



For Review O

nly

6

(Stephen Fox, then with Agriculture and AgriFood Canada), selected for their yield, quality

and disease resistance. Head selections were conducted by a team of breeding technicians

under the supervision of Stephen Fox with input and some direct involvement of the organic

agriculture team at the University of Manitoba. Plants in the nursery were evaluated

approximately every 10 days from heading to maturity. Plants with robust growth, absence

of disease and strong tillering were marked with tags. At maturity, heads from a portion of

these plants were selected, threshed and planted in “head rows” the following year, and

approximately 40 of these lines were grown in small plots in subsequent years. At the F4,

yield and grain protein were measured on all lines and the 14 lines with the highest protein

yield (protein content multiplied by seed yield) were selected for inclusion as organic lines in

the present study. Commercial checks consisted of four cultivars grown widely in Western

Canada; Kane, McKenzie, 5602HR, and AC Cadillac. McKenzie and AC Cadillac are

among the most popular wheat cultivars on organic farms in the eastern Prairies (Fox, pers.

comm.).

To provide a uniform seed source for the experiments, seeds of all lines and cultivars

were grown at Glenlea, Carman, and Oxbow in 2008 were evenly blended based on kernel

weight and germination rates for seeding the 2009 sites. Seed produced at each location in

2009 was retained and used to seed at the same site it was collected from for the 2010 trials.

Genotypes were compared in a randomized complete block design with four

replicates at all study sites. Each treatment plot was seeded with a main plot that split into

two 4-row sub-plots. Row spacing was 15 cm and rows were 8 m in length. One sub-plot per

treatment was randomly selected and used for in season biomass sampling and the other sub-

plot was left undisturbed for yield measurement. Border rows of fall rye were seeded between

plots and sub-plots and border plots of wheat were sown on either side of each trial to

minimize edge effects.

Page 6 of 25



For Review O

nly

7

Field Trial Management

The land was prepared immediately before seeding using one pass with a field

cultivator followed by harrowing. Plots were seeded using a disk drill (Fabro Industries,

Swift Current, Saskatchewan). Plots were seeded into moisture (approximately 2.5 – 5 cm) at

all sites with an approximate density of 333 viable kernels m-2

. Seeding and harvest dates

were June 3 and Sept. 25 at Glenlea in 2009, May 20 and August 27 at Oxbow in 2009, May

13 and August 23 at Carman in 2010 and May 14 and August 26 at Oxbow in 2010.

Data Collection

Wheat plant population density was measured on 2, 3m randomly selected row

lengths per plot when plants were at the 3 leaf stage. Crop height measurements were taken

at maturity by measuring the distance from the soil to tip of spike (not including awns) in 10

plants within each experimental unit. Aboveground biomass was measured twice during the

growing season; at anthesis (Zadoks et al. 1974 – stage 65), and late dough stage (Zadoks

stage 87). At Glenlea in 2009, a biomass measure at wheat stem elongation (Zadoks stage

32) was also included. In all cases, plants were cut at ground level (0- 2.5 cm). Material was

dried at 70°C for 48 hours after being collected. Dried biomass samples from each sampling

were weighed to assess dry matter (DM) value for each sample.

Prior to grain harvest, the ends of plots were trimmed and individual plot area

measured. Plots were harvested using a Wintersteiger plot harvester (Model ‘Nurserymaster

Elite’) except at Oxbow in 2009 where they were hand harvested and threshed using a custom

designed belt thresher. The harvested area was between 6.1 and 7.3 m2 depending on

location. Grain samples were dried for 48 hours on a forced air drying bed or on drying racks

prior to cleaning. Grain samples were cleaned to remove excess chaff and weed seeds using a

Page 7 of 25



For Review O

nly

8

Carter Day Dockage Tester (model- 31624/W-3301). The dockage tester contained a no. 1

riddle, 9/64 tri double cut sieve, and an S-909 S1/2 164 R.086 sieve. Two hundred and fifty

seeds were counted in order to determine kernel mass using a seed counter (Old Mill Model

850-3). The kernel number (KNO) per unit of area as well as KNO per unit of dry matter at

anthesis (KNO:DMa) was calculated by dividing the number or kernels produced per hectare

by the kilograms of yield per hectare. Grain Harvest Index (HI) was also calculated. An index

of grain yield per unit of dry matter accumulated at anthesis was calculated and is referred to

as the mid-season harvest index (MS-HI).

The nitrogen content of above ground biomass and grain was measured. Dried

biomass tissue samples were ground using a Wiley Mill No.1 with a 2mm screen (Arthur H.

Thomas Co., Philadelphia). A sub-sample of each grain sample was ground using a cyclone

sample mill. A sub-sample of the ground tissue and flour samples were analyzed for nitrogen

content using a LECO FP-528 (LECO, St. Joseph) combustion analyzer. Biomass N

accumulation was calculated as biomass yield x biomass N concentration. Grain N yield was

calculated as grain yield x grain N concentration.

Data Analysis

Cultivar differences were tested using analysis of variance for all measurements. Data

sets were analyzed using the PROC Mixed procedure with the Statistical Analysis Software

program (SAS Institute 2001). Wheat genotypes were considered as fixed effects and

replications and site-years as random effects for all measurements. Assumptions of ANOVA

were tested by using the PROC Univariate procedure. Differences were considered

significant at p <0.05.

The Shapiro-Wilk test W-statistic test indicated some non-normal results and Square

Root transformations were required for crop height, final biomass, grain N yield and

Page 8 of 25



For Review O

nly

9

KNO:Dma. In order to combine the four site-years and perform a combined analysis of the

data, the variances within the data were tested to ensure they were not significantly different.

Using Bartletts test for homogeneity (p > 0.05) it was found that data from the four site years

had equal variances for all parameters except plant height and thousand kernel weight.

Transformation did not help to normalize these parameters, so plant height and thousand

kernel weight results are presented as individual site years.

Means of all organic vs. conventional lines were also tested in an orthogonal contrast.

RESULTS AND DISCUSSION

Establishment, growth and grain yield

No differences were observed among wheat genotypes for plant population density

(Table 4). Average stand density ranged from 212 to 264 plants m-2

, close to the 230 to 280

plants m-2

recommended by Manitoba Agriculture, Food and Rural Initiatives (2013). Above

ground biomass production at anthesis and dough development stages was also unaffected by

wheat genotype (Table 4). Examining spring wheat biomass at anthesis when grown without

N fertilizer, Noulas et al. (2013) also observed no significant differences between genotypes.

Weed biomass at time of grain harvest was low in the present study (less than 10% of total

aboveground biomass) except at Oxbow in 2010 where wild oat (Avena fatua) biomass

averaged 2,000 kg ha-1

(approximately 40% of total aboveground biomass).

Grain yield ranged from trial means of 1837 kg ha-1

at Oxbow in 2010 to means of

4337 kg ha-1

at Carman in 2010. Grain yield at Oxbow in 2010 was close to the long-term

on-farm average (Entz et al. 2001).

Combined analysis for yield showed significant differences among genotypes. All

organically-selected lines (ORG), with the exception of ORG 6, 9 and 10, yielded

significantly more than the check cultivars. ORG 7 was the highest yielding line across site-

Page 9 of 25



For Review O

nly

10

years, with an average yield of 3568 kg ha-1

(Table 4). Averaged over site-years, the top five

yields were all organic lines while the lowest yielding cultivar was the check cultivar ‘Kane’,

which had an average yield of 2895 kg ha-1

. Cadillac’ was the only check cultivar that yielded

more than any organic line. As a group, organic lines yielded 456 kg ha-1

more (contrast

P<0.05) than the check cultivars (Table 4). Kirk et al. (2012) also observed higher grain

yield when wheat genotypes were selected under organic vs conventional management.

Grain yield differences were observed at all 4 site-years. The significant genotype x

site-year interaction (Table 4) was attributed to small differences in the ranking of cultivars

and lines between site-years and no consistent cross-over interaction was observed (data not

shown).

Across all site-years, organic lines were 7 to 10 cm shorter than check cultivars (Table

5). The magnitude of the height differences differed by site (Table 5). The shortest crops

overall (average 78 cm) and the smallest height differences between organic and check

cultivars were observed at Oxbow in 2009. Our results are opposite to Kirk et al. (2012) who

observed that organically-selected wheat populations were taller than the same population

selected under conventional management. It has been previously reported that taller varieties

are more competitive and thus better suited for organic conditions (Gooding et al. 1993;

Cudney et al. 1991). A shorter planophile cultivar with a high leaf area index and vigorous

early season growth may be more competitive than a tall cultivar that lacks those traits

(Wolfe et al. 2008; Lammerts van Bueren et al. 2011). Tallness was included in Mason et

al’s. (2007) ideotype description for organic spring wheat.

Yield Efficiency

The parameters used to describe yield efficiency in this study included HI, KNO,

KNO:biomass at anthesis; and grain yield:biomass at anthesis (Fisher and Kohn 1966; Entz

Page 10 of 25



For Review O

nly

11

and Fowler 1990). Harvest index was significantly higher for organic lines (average 0.43)

compared with check cultivars (average 0.37). Therefore, while aboveground biomass was

similar in organic lines and check cultivars, organic lines were able to shift a higher

proportion of that biomass to grain (Table 4) (Fischer and Kohn 1966; Barraclough et al.

2014). Among organic selections, ORG 7, 11 and 12 tied for the highest HI (0.44) while the

check cultivar ‘McKenzie’ had the lowest HI (0.35). In the present study, greater HI

corresponded with decreases in plant height. Brancourt-Hulmel et al. (2003) reported HI

increases were associated with reduced plant height and reduce lodging.

Hay (1995) found HI to be more stable than yield when measured in different

environments and concluded that HI may be a superior parameter to utilize when comparing

the performance of breeding lines across varying environments. The lack of a significant

genotype x site-year interaction for HI compared with the presence of such an interaction for

grain yield (Table 4) lends support to Hay’s assertion.

Contrast results for mid-season harvest index (ie., grain yield per unit of biomass at

anthesis) also showed an advantage for the organically-selected lines (Table 4). Yield:DMa

averaged 62% for organic lines compared with 52% for the check cultivars. Greater grain

yield per unit of biomass at anthesis may be due to greater mobilization of pre-anthesis

resources during grain filling (Fischer and Kohn 1966), greater de novo assimilation during

grain filling (Fischer and Edmeades 2010), higher plant productivity from a ‘stay green’ trait

due to a longer period of active photosynthesis (Gregersen et al. 2008), or a combination of

these factors. Greater grain yield per unit of pre-anthesis biomass may make genotypes more

tolerant of pre-anthesis growth limiting factors such as weed interference or slow N

mineralization from the soil organic matter. These processes require further investigation.

Kernel number per unit area of land (KNO) is recognized as an important component

determining final grain yield in sink limited crops such as wheat (Doyle and Fischer 1979;

Page 11 of 25



For Review O

nly

12

Bindraban et al. 1998). Greater (P<0.05) KNO for organic lines than check cultivars

(average 679 kernels m-2

) indicates that organic lines developed a larger sink than the check

cultivars (Fischer and Edmeades 2010). KNO was highly (P<0.01) correlated with grain

yield (r=0.94**), HI (r=0.54**) and final biomass (r=0.59**), supporting previous work (eg.

Entz and Fowler 1990; Donmez et al. 2001).

Kernel number per unit of dry matter at anthesis (KNO:DMa) has been referred to as

the kernel production efficiency (Fischer 1979). Organic lines produced an average 2,016

more kernels per unit of biomass at anthesis than the checks. Because KNO is set by

anthesis, greater kernel production per unit of anthesis biomass points to an assimilate

partitioning advantage for organically-selected lines during the pre-anthesis period.

Among genotypes, ORG 9 had the highest kernel production efficiency while the

check cultivar ‘McKenzie’ had the lowest. The lowest average kernel production efficiency

was observed at the weedy site-year (Oxbow 2010); however the lack of a significant

interaction between genotype and site-year indicated that kernel production efficiency

differences between genotypes were stable across sites (Table 4).

Significant differences were also observed for kernel mass (Table 6). Contrast

performed between the organic lines and check cultivars found the organic lines to have

significantly higher kernel mass at all four site years (Table 6). A slight positive correlation (r

= 0.29**) was observed between kernel mass and grain yield. Kirk et al. (2012) also found

that wheat selected under organic management had higher kernel mass than the same

populations selected under conventional management.

In summary, based on contrast analysis, the organically selected lines had similar total

above ground biomass compared with the check cultivars, but they were able to transfer a

higher proportion of that biomass to seed. Greater HI for organic lines points to improved

assimilate partitioning after anthesis suggesting that traits like ‘stay green’ (Gregerson et al.

Page 12 of 25



For Review O

nly

13

2008) or better disease resistance (Fernandez et al. 2014) may have been involved. At the

same time, higher kernel production efficiency (ie., KNO:DMa) for organic lines suggests

that assimilate partitioning advantages for the organic lines also occurred before flowering.

Even kernel mass, often associated with post-anthesis growing conditions, can be influenced

by conditions before anthesis (ie., carpel size) (Calderini and Reynolds 2000). Pre-anthesis

assimilate advantages for organic lines are important since pre-anthesis dry matter

accumulation in organic production can be limited by early season weed interference and

limited availability of N from the soil organic matter (Cicek et al. 2014).

N Uptake and grain protein

N uptake at the dough development stage in the present study averaged close to 90 kg

N ha-1

; similar values were reported for organic wheat grown after a pea/oat green manure

(Cicek et al. 2014) and conventionally fertilized wheat (Malhi et al. 2006). Generally, there

was little difference among genotypes for plant biomass N uptake at anthesis or maturity

(Table 7). Only one significant effect was observed, that of greater tissue N concentration at

anthesis for organic over check cultivars (Table 7).

As a group, the organically-selected lines had lower grain protein content compared

with check cultivars (Table 7). One explanation is protein dilution due to higher grain yield.

Our results differ from those of Kirk et al. (2012) who observed both higher grain protein and

yield in organically-selected lines compared to those selected in a conventional environment.

The lack of a significant genotype x site-year interaction indicates that lower grain

protein in organic lines was consistent across site-years. The cultivar ‘Cadillac’ had the

highest average protein of 142 g kg−1

while ORG10 was found to have the lowest average

grain protein with an average of 130 g kg−1

. Average protein values in this study ranged

Page 13 of 25



For Review O

nly

14

between 116 and 155 g kg−1

and would be considered adequate to low according to the

Canadian Grains Commission grain grading guide (Canadian Grain Commission 2013).

Wolfe et al. (2008) stated that grain protein in organic agriculture needs to be higher

in order to compensate for the relatively lower N availability compared to conventional

systems, while Lammerts van Bueren et al. (2002) suggested that organic cultivars should

have larger and more active root systems for increased nutrient uptake in order to cope with

the lower nutrient levels of organic fields. In the present study, soil N levels were adequate

(Table 1) and no differences in wheat plant N uptake was recorded (Table 7).

N uptake into harvested seed is an indirect measure of N use efficiency. This measure

is also simpler to use than plant N biomass when screening breeding populations for N

sufficiency (Fowler et al. 1990). In our study, total grain N yield was higher in organic lines

than check cultivars (Table 7). However, greater ability to assimilate N did not translate into

similar or higher grain N concentration (ie., grain protein content), despite the fact that total

grain N yield and grain protein content were correlated (r=0.68**). Therefore, it appears that

organic lines were still better able to assimilate carbohydrates than N, resulting in more

protein dilution than check cultivars.

Summary and Conclusions

This preliminary study measured seasonal crop growth, yield and N uptake of

advanced wheat breeding lines after 6 and 7 years of selection with commercial check

cultivars. An important finding was that higher grain yield (P<0.05) in organic lines were not

associated with taller stature or greater above-ground biomass accumulation; no differences

for these parameters were observed. Where organic lines differed from the check cultivars

was in assimilate partitioning; both pre- and post-anthesis assimilate partitioning was greater

for organic lines. Superior pre-anthesis assimilate partitioning is of particular interest given

Page 14 of 25



For Review O

nly

15

the challenges of weeds and N supply that organic crops face early in the season. Future

research using organic vs conventional selection of the same wheat populations (such as the

Kirk et al. 2012 study) is required to confirm our preliminary observations.

Despite having more N uptake into grains, most organically-selected lines had lower

grain protein concentrations than conventional check cultivars. Therefore, our selection

approach was better at increasing grain yield than grain N concentration even though

selections were screened for grain protein in the F4 generation. The limiting factor to N

economy did not appear to be soil N availability; available N levels were high at all site-

years.

Acknowledgements

The authors gratefully acknowledge the expert technical assistance of Keith Bamford

(University of Manitoba) and Denis Green (Agriculture and AgriFood Canada). The senior

author received a scholarship from the Natural Sciences and Engineering Research Council

of Canada and the Canadian Wheat Board.

Page 15 of 25



For Review O

nly

16

LITERATURE CITED 1

2 Barraclough, P.B, Lopez-Bellido, R. and Hawkesford, M.J. 2014. Genotypic variation in the 3

uptake, partitioning and remobilization of nitrogen during grain-filling in wheat. Field Crops 4

Research. 156: 242-248. 5

6

Brancourt-Hulmel, M., Doussinault, G.,Lecomte, C., Berard, P.,Le Buanec, B. and Trottet, 7

M. 2003. Genetic Improvement of Agronomic Traits of Winter Wheat Cultivars Released in 8

France from 1946 to 1992. Crop Sci. 43:37–45. 9

10

Calderini, D.F. and Reynolds, M.P. 2000. Changes in grain weight as a consequence of de-11

graining treatments at pre- and postanthesis in synthetic hexaploid lines of wheat (Triticum 12

durum × T. tauschii). Australian Journal Plant Physiol. 27: 183–191. 13

14

Canadian Grain Commission. 2013. Quality of western Canadian wheat 2011: CWRS – 15

Protein and variety survey. [Online] Available: 16

http://www.grainscanada.gc.ca/wheat-ble/harvest-recolte/2011/hqww/hqww11-qrbo11-3-17

eng.htm [2013 Sept 2] 18

19

Canadian Agricultural Services Coordinating Committee. 1998. Soil Classification Working 20

Group, National Research Council Canada, Canada. Agriculture, and Agri-Food Canada. 21

Research Branch. The Canadian system of soil classification. No. 93. NRC Research Press. 22

23

Carr, P.M., Kandel, H.J., Porter, P.M., Horsley, R.D. and Zwinger, S.F. 2006. Wheat 24

Cultivar Performance on Certified Organic Fields in Minnesota and North Dakota. Crop Sci. 25

46:1963-1971. 26

27

Cicek, H., Thiessen Martens, J.R., Bamford, K.C. and Entz, M.H. 2014. Effects of grazing 28

two green manure crop types in organic farming systems: N supply and productivity of 29

following grain crops. Agric. Ecosys. Environ. 190:27-36. 30

31

Cudney, D.W., Jordan, L.S. and Hall, A.E. 1991. Effect of wild oat (Avena fatua) infestations 32

on light interception and growth rate of wheat (Triticum aestivum). Weed Science 39: 175-33

179. 34

35

Dawson, J.C., Huggins, D.R. and Jones, S.S. 2008. Characterizing nitrogen use efficiency in 36

natural and agricultural ecosystems to improve the performance of cereal crops in low-input 37

and organic agricultural systems. Field Crops Research. 107: 89-101. 38

39

Donmez, E., Sears, R.G., Shroyer, J.P. and Paulsen, G.M. 2001. Genetic Gain in Yield 40

Attributes of Winter Wheat in the Great Plains. Crop Sci. 41: 1412-1419. 41

42

Doyle, A.D. and Fisher, R.A. 1979. Dry matter accumulation and water use relationships in 43

wheat crops. Austr. J Agric Res. 30:815-829. 44

45

Entz, M.H. and Fowler, D.B. 1990. Differential Agronomic Response of Winter Wheat 46

Cultivars to Preanthesis Environmental Stress. Crop Sci. 30: 1119-1123. 47

48

Page 16 of 25



For Review O

nly

17

Entz, M.H., Guilford, R. and Gulden, R. 2001. Crop yield and soil nutrient status on 14 49

organic farms in the eastern portion of the northern great plains. Can. J. Plant Sci. 81: 351-50

354. 51

52

Environment Canada. 2011a. Canadian climate normals 1971-2000. [Online] Available: 53

http://www.climate.weatheroffice.ec.gc.ca/climate_normals/index_e.html [2011 April 12]. 54

55

Environment Canada. 2011b. National climate data and information archive. [Online] 56

Available: http://climate.weatheroffice.ec.gc.ca/climateData/canada_e.html [2011 March 29]. 57

58 Fernandez, M. R., Fox, S. L., Hucl, P. and Singh, A. K. 2014. Leaf spotting reaction of spring 59

common, durum and spelt wheat, and Kamut under organic management in western Canada. 60

Can. J. Plant Sci. 94: 929–935. 61

62 Fischer, R. A. 1979. Growth and water limitation to dryland wheat yield in Australia: a 63

physiological framework (review). J. Australian Institute of Agricultural Science. 64

65

Fischer, R.A., and Kohn, G.D. 1966. The relationship of grain yield to vegetative growth and 66

post-flowering leaf area in wheat crop under conditions of limited soil moisture. Austr J 67

Agric Res 17: 281-295. 68

Fischer, R. A. and Edmeades, G.O. 2010. Breeding and Cereal Yield Progress. Crop Sci. 69

50:85-98. 70

Fowler, D.B., Brydon, J., Darroch, B.A., Entz, M.H. and Johnston, A.M. 1990. Environment 71

and Genotype Influence on Grain Protein Concentration of Wheat and Rye. Agron. J 82:655-72

664. 73

74

Gooding, M.J., Thompson, A.J. and Davies, W.P. 1993. Interception of photosynthetically 75

active radiation, competitive ability and yield of organically grown wheat varieties. Asp App 76

Biol. 34: 355-362. 77

78

Gregersen P.L., Holm P.B. and Krupinska K. 2008. Leaf senescence and nutrient 79

remobilization in barley and wheat. Plant Biology. 10: 37-49. 80

81

Hay, R.K.M. 1995. Harvest index: a review of its use in plant breeding and crop physiology. 82

Ann. Appl. Biol. 126: 197-216. 83

84

Kirk, A.P., Entz, M.H., Fox, S.L. and Tenuta, M. 2011. Mycorrhizal colonization, P uptake 85

and yield of older and modern wheats under organic management. Can. J. Plant Sci. 91: 663–86

667. 87

88

Kirk, A.P., Fox, S.L. and Entz, M.H. 2012. Comparison of organic and conventional 89

selection environments for spring wheat. Plant Breeding. 131: 697-694. 90

91

Kronberga, A., Legzdioa, L., Strazdioa, V. and Vicupe, Z. 2013. Comparison of selection 92

results in organic and conventional environments for winter triticale. Proc. Latvian Academy 93

of Sciences 67:268-271. 94

Page 17 of 25



For Review O

nly

18

95

96

Lammerts van Bueren, E.T., Struik, P.C. and Jacobsen, E. 2002. Ecological concepts in 97

organic farming and their consequences for an organic crop ideotype. Neth. J. Agric. Sci. 50: 98

1-26. 99

100

Lammerts van Bueren, E.T., Jones, S.S., Tamm, L., Murphy, K.M., Myers, J.R, Leifert, C. 101

and Messmer, M.M. 2011. The need to breed crop varieties suitable for organic farming, 102

using wheat, tomato, and broccoli as examples: A review. NJAS – Wageningen Journal of 103

Life Sciences. 58: 193-205. 104

105

Macey, A. 2010. Certified Organic Production Statistics for Canada 2010. 106

https://www.cog.ca/uploads/Certified%20Organic%20Statistics%20Canada%202010.pdf 107

108

MAFRI (Manitoba Agriculture, Food and Rural Initiatives). 2011. Manitoba Ag-Weather 109

Program. [Online] Available: http://tgs.gov.mb.ca/climate [2011 April 28]. 110

111

MAFRI (Manitoba Agriculture, Food and Rural Initiatives). 2013. Spring Wheat Production 112

Guide [Online] Available: 113

http://www.gov.mb.ca/agriculture/crops/cereals/bff01s01.html#fertilizer [2013 June 10] 114

115

Malhi, S.S., Johnston, A.M., Schoenau, J.J, Wang, Z.H. and Vera, C.L. 2006. Seasonal 116

biomass accumulation and nutrient uptake of wheat, barley and oat on a Black Chernozem 117

soil in Saskatchewan. Can. J. Plant Sci. 86: 1005-1014. 118

119

Martens, G., Lamari, L., Grieger, A., Gulden, R. H. and McCallum, B. 2014. Comparative 120

yield, disease resistance and response to fungicide for forty-five historic Canadian wheat 121

cultivars. Can. J. Plant Sci. 94: 371–381. 122

123

Mason, H., Navabi, A., Frick, B., O’Donovan, J., Niziol, D. and Spaner, D. 2007. Does 124

growing Canadian Western Hard Red Spring wheat under organic management alter its 125

breadmaking quality? Renewable Agriculture and Food Systems. 22: 157-167. 126

127

Mason, H., Goonewardene, L., and Spaner, D. 2008. Competitive traits and the stability of 128

wheat cultivars in differing natural weed environments on the northern Canadian Prairies. J. 129

Agr. Sci. 146: 21-33. 130

131

Murphy, K.M., Campbell, K.G., Lyon, S.R. and Jones, S.S. 2007. Evidence of varietal 132

adaptation to organic farming systems. Field Crops Research. 102: 172-177. 133

134

Murphy, K.M., Reeves, P.G. and Jones, S.S. 2008. Relationship between yield and mineral 135

nutrient concentrations in historical and modern spring wheat cultivars. Euphytica. 163: 381-136

390. 137

138

Nelson, A.G., Quideau, S., Frick, B., Niziol, D., Clapperton, J. and Spaner, D. 2011. Spring 139

wheat genotypes differentially alter soil microbial communities and wheat breadmaking 140

quality in organic and conventional systems. Canadian Journal of Plant Science. 91: 485-495. 141

142

Page 18 of 25



For Review O

nly

19

Noulas, C., Alexiou, I., Herrera, J.M. and Stamp, P. 2013. Course of Dry Matter and 143

Nitrogen Accumulation of Spring Wheat Genotypes known to vary in parameters of Nitrogen 144

use efficiency. Journal of Plant Nutrition 36: 1201-1218. 145

146

Pridham, J.C., Entz, M.H., Martin, R.C. and Hucl, P.J. 2007. Weed, disease and grain yield 147

effects of cultivar mixtures in organically managed spring wheat. Can J Plant Sci. 87:855-148

859. 149

150

Reid, T.A., Navabi, A., Cahill, J.C., Salmon, D. and Spaner, D. 2009. A genetic analysis of weed 151 competitive ability in spring wheat. Can. J. Plant Sci. 89: 591-599. 152 153

Wang, H., McCaig, T.N., DePauw, R.M., Clarke, F.R. and Clarke, J.M. 2003. Physiological 154

characteristics of recent Canada Western Red Spring wheat cultivars: Components of grain 155

nitrogen yield. Can. J. Plant Sci. 83: 699-707. 156

157

Wolfe, M.S., Baresel, J.P., Desclaux, D., Goldringer, I., Hoad, S., Kovacs, G., 158

Loschenberger, F., Miedaner, T., Ostergard, H. and Lammerts van Bueren, E.T. 2008. 159

Developments in breeding cereals for organic agriculture. Euphytica. 163: 323-346. 160

161

Zadoks, J. C., Chang, T.T. and Konzak, C.F. 1974. A decimal code for the growth stages of 162

cereals. Weed research. 14: 415-421. 163

164

165

166

Page 19 of 25



For Review O

nly

20

Table 1: Soil nutrient status and crop history at experimental site-years in 2009 and 2010. 167

Parameters include nitrate-N (N), available phosphorous (Olsen P), potassium (K), zinc (Zn), 168

pH, organic matter (OM) and previous crop. 169

Site

Location Year

N

(0-15

cm)

N

(15-60

cm)

N

(60-120

cm)

P-

Olsen K Zn

pH OM (%) Previous Crop

---------kg ha-1--------- ----------ppm-----------

Glenlea 2009 17.9 151.2 89.6 6.0 91.0 0.4 7.4 4.7 Pea Green Manure

Oxbow 2009 45.9 137.8 35.8 9.0 363.0 0.9 7.2 3.2 Fallow with pea

green manure

Carman 2010 32.7 95.9 67.0 6.0 397.0 0.6 5.7 4.6 Green manure

Oxbow 2010 29.7 66.2 33.5 18.0 310.0 2.2 7.9 3.1 Alfalfa seed crop

170

171

172

173

174

175

Table 2: Average daily temperatures during the growing season (May 1st – August 31st) at 176

each experiment site (Environment Canada 2011a), and 30-year normals (Environment 177

Canada 2011). 178

Research

Site

Average Daily Temperature (ºC)

Normala

2009 2010

May June July Aug May June July Aug May June July Aug

Carman 12.4 17.2 19.7 18.1 - - - - 11.6 16.7 20.1 19.3

Glenlea 12.4 17 19.3 18.4 9.6 17.1 18.4 18.8 - - - -

Oxbow 12.1 16.8 19.5 18.6 9.9 15.1 16.5 17 10.1 16.1 18.5 18.5

a30-year normals. 179

180

181

182

183

184

185

186

187

188

189

Page 20 of 25



For Review O

nly

21

Table 3: Precipitation during the growing season (May 1st – August 31st) at each experiment 190

site (Environment Canada 2011a), and as a percent of 30-year normals (Environment Canada 191

2011). 192

Research

Site

Precipitation (mm)

Normala 2009 2010

May June July Aug May June July Aug May June July Aug

Carman 61.1 75.5 73.5 66.8 - - - - 132.1 50.4 47.2 152.3

Glenlea 62.1 93.8 80.1 67.7 78.1 82.8 120.6 52.0 - - - -

Oxbow 55.6 76.3 65.0 49.5 6.6 66.4 37.6 71.6 88.5 133.6 55.4 86.4

a30-year normals. 193

194

195

196

Page 21 of 25



For Review Only

22

Table 4: Crop growth and yield parameters measured for advanced lines and check cultivars. Data averaged over the four site-years. 197

Stand Density Anthesis

Biomass Weight Soft Dough

Biomass Weight Harvest Index

Yield per DM at Anthesis

Kernel Density KNO per Unit of DM at Anthesis

Yield

plants m-2 kg ha

-1 kg ha

-1 m

-2 kg ha

-1

Site-year

Glenlea 2009 212 b 5213 b 8491 b 0.39 c 0.63 a 10817 b 21338 a 3216 b

Oxbow 2009 - - 7900 c 0.43 b - 9141 c - 3280 b

Carman 2010 253 a 6711 a 10362 a 0.48 a 0.66 a 13632 a 20715 a 4337 a

Oxbow 2010 264 a 4226 c 5329 d 0.32 d 0.45 b 6053 d 14893 b 1836 c

Genotype

ORG 2 242 5452 8536 0.42 abcd 0.62 abc 10332 abcd 18905 bcd 3559 a

ORG 3 240 5541 7504 0.44 abc 0.65 ab 10691 abc 20547 abc 3512 ab

ORG 4 248 5245 8113 0.44 abc 0.61 abcd 10217 abcd 19356 bcd 3352 ab

ORG 6 240 4865 7595 0.39 cd 0.60 abcde 9236 e 19846 abc 2917 d

ORG 7 236 5481 8032 0.46 ab 0.60 abcde 10936 ab 19374 abc 3568 a

ORG 9 233 5120 7699 0.4 bcd 0.66 ab 10665 abcd 22610 a 3221 bcd

ORG 10 250 5569 8447 0.41 abcd 0.55 cdef 10101 bcde 17769 cd 3321 abc

ORG 11 248 5499 8210 0.47 a 0.62 abc 11189 a 21132 ab 3456 ab

ORG 12 229 5453 8087 0.45 abc 0.60 abcde 10269 abcd 18394 bcd 3494 ab

ORG 13 263 5352 8528 0.42 abcd 0.62 abc 10545 abcd 19584 bcd 3504 ab

ORG 14 242 4914 8060 0.44 abc 0.70 a 10185 bcde 21302 ab 3453 ab

CADILLAC 238 4963 7598 0.37 d 0.57 bcdef 9718 cde 19292 bcd 3004 cd

KANE 246 5754 7808 0.36 d 0.52 def 9723 cde 18012 cd 2895 d

MCKENZIE 239 6044 8305 0.35 d 0.49 f 9689 de 16652 c 2914 d

5602HR 247 5454 7783 0.41 abcd 0.51 ef 9755 cde 17978 cd 2932 d

Source of Variation ---------------------------------------------------------------------------- P > F ----------------------------------------------------------------------------

Site-year (SY) 0.0075 <.0001 <.0001 0.0252 0.002 <.0001 0.0003 <.0001

Genotype 0.6915 0.0558 0.6607 0.0089 0.0019 0.0018 0.0213 <.0001

SY X Genotype 0.8716 0.0983 0.1898 0.1103 0.2493 0.0014 0.3232 0.004

Contrast ---------------------------------------------------------------------------- P > F ----------------------------------------------------------------------------

Organic vs. Checks 0.9479 0.0933 0.3733 <.0001 <.0001 0.0004 0.0015 <.0001

Estimate -0.3525 240.84 -200.2 -5.9782 -0.09738 -679.45 -2016.67 -455.94

Page 22 of 25



For Review O

nly

23

23

Table 5: Plant height at maturity for advanced lines and check cultivars grown at four site-

years.

Genotype

Glenlea 2009 Oxbow 2009 Carman

2010 Oxbow 2010

------------------------------------- cm --------------------------------

ORG 2 102.4 cde 79.6 bcd 89.7 efg 95.7 c

ORG 3 98.8 fg 77.1 cdef 91.5 def 87.7 f

ORG 4 103.0 cd 77.1 cdef 90.3 defg 91.8 cdef

ORG 6 100.5 def 75.6 def 85.8 g 90.6 def

ORG 7 100.5 def 78.2 bcde 93.1 cde 95.0 cd

ORG 9 95.9 h 75.0 def 95.0 cd 92.0 cdef

ORG 10 98.8 fg 80.9 bc 87.0 fg 88.9 ef

ORG 11 100.3 efg 77.0 cdef 93.3 cde 95.6 c

ORG 12 98.6 fg 78.7 bcd 87.9 fg 87.7 f

ORG 13 97.8 gh 73.5 ef 90.9 def 94.5 cd

ORG 14 101.8 de 77.9 cde 93.8 cde 92.9 cde

CADILLAC 117.8 a 89.2 a 109.0 a 109.2 a

KANE 100.0 efg 72.8 f 95.1 cd 95.3 c

MCKENZIE 109.6 b 76.2 cdef 102.0 b 103.5 b

5602HR 104.4 c 82.9 b 96.9 c 100.8 b

P > F <0.0001 <0.0001 <0.0001 <0.0001

Contrast --------------------------------P > F--------------------------------

Organic vs Checks <0.0001 0.0059 <0.0001 <0.0001

Estimate 8.0955 2.9454 9.9858 10.1625

Page 23 of 25



For Review O

nly

24

24

Table 6: Seed weight for advanced lines and check cultivars grown at four site-years.

Genotype

Glenlea 2009 Oxbow 2009 Carman 2010 Oxbow 2010

------------------------------ mg seed-1------------------------------

ORG 2 33.83 abc 40.73 bc 36.81 a 36.77 a

ORG 3 33.04 abcd 38.14 ef 35.87 ab 31.46 cde

ORG 4 32.17 bcdefg 39.98 bcd 35.51 abc 34.61 ab

ORG 6 31.68 cdefgh 38.94 de 33.03 defg 32.92 bcd

ORG 7 32.34 abcdef 39.60 cd 34.39 bcd 33.59 bc

ORG 9 29.46 h 36.68 gh 32.54 efg 31.24 de

ORG 10 32.90 abcde 40.31 bc 33.87 ab 33.55 bc

ORG 11 30.41 fgh 37.54 fg 33.12 def 31.15 de

ORG 12 34.44 a 40.85 ab 35.86 ab 34.71 ab

ORG 13 31.75 cdefg 41.07 ab 35.84 ab 33.89 b

ORG 14 34.21 ab 41.99 a 35.57 ab 34.82 ab

CADILLAC 31.21 defgh 36.01 h 33.44 def 30.43 e

KANE 30.75 efgh 34.42 I 32.03 fg 31.13 de

MCKENZIE 32.02 bcdefg 33.21 I 32.91 defg 29.50 e

5602HR 30.07 gh 36.79 gh 31.44 g 29.77 e

P > F 0.0006 <0.0001 <0.0001 <0.0001

Contrast ------------------------------------------P > F--------------------------------

Organic vs Checks 0.0045 <0.0001 <0.0001 <0.0001

Estimate -1.3717 -4.5144 -2.3109 -3.3086

Page 24 of 25



For Review O

nly

25

25

Table 7: Nitrogen parameters measured for advanced lines and check cultivars. Data

averaged over the four site-years.

Anthesis biomass N

Anthesis biomass N

Soft Dough biomass N

Soft Dough biomass N

Protein Grain N Yield

kg ha-1

g kg−1 Kg ha-1

g kg−1 g kg−1 kg ha-1

Site-year

Glenlea 2009 88.8 b 17.1 a 103.8 b 1.23 a 155 a 87.5 b

Oxbow 2009 - - 86.0 c 1.07 b 128 c 73.7 c

Carman 2010 115.1 a 17.1 a 134.3 a 1.28 a 142 b 108.6 a

Oxbow 2010 48.9 c 11.6 b 44.1 d 0.82 c 116 d 36.9 d

Genotype

ORG 2 92.0 16.5 a 93.9 1.07 139 abcd 88 a

ORG 3 86.9 15.5 abc 92.4 1.19 141 ab 88.6 a

ORG 4 85.1 15.6 abc 99.4 1.15 139 abcd 83.1 abc

ORG 6 75.2 15.2 abcd 77.2 0.98 140 abc 72.6 d

ORG 7 93.1 16.6 a 91.9 1.13 136 bcde 85.6 ab

ORG 9 83.7 15.9 ab 86.4 1.08 134 def 76.7 bcd

ORG 10 82.1 13.9 c 96.7 1.08 128 f 76.1 cd

ORG 11 83.9 14.9 bcd 81.0 1.02 128 f 79.2 abcd

ORG 12 84.6 15.1 abcd 87.3 0.98 135 cde 83.2 abc

ORG 13 84.7 15.5 abc 109.7 1.21 136 abcde 85.4 ab

ORG 14 83.6 16.0 ab 95.2 1.12 133 ef 82.5 abc

CADILLAC 78.9 15.4 abcd 80.6 0.99 142 a 76.6 bcd

KANE 87.8 14.9 bcd 98.2 1.20 140 abc 72.8 d

MCKENZIE 85.5 14.0 cd 103.1 1.22 138 abcde 72.0 d

5602HR 79.5 14.3 cd 88.3 1.08 140 ab 74.0 cd

Source of Variation

Site-year (SY) <0.0001 <.0001 <.0001 0.0015 <0.0001 <0.0001

Genotype 0.6055 0.0212 0.3707 0.2442 <0.0001 0.0003

SY X Genotype 0.6984 0.7986 0.7215 0.73 0.1228 0.027

Contrast

Organic vs. Checks

0.5467 0.0088 0.9124 0.4983 <0.0001 <0.0001

Estimate -1.7955 -0.08875 0.5418 0.02918 0.5184 -8.0269

Page 25 of 25



Documents

For Review Only - University of Toronto T-Space · For Review Only 1 Organic selection may improve yield efficiency in spring wheat: A preliminary analysis. Laura Wiebe 1, Stephen