Keeping the yam 'a part of man

International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

Keeping the yam ‘a part of man’

- a breeder’s contribution

Robert Asiedu

Institut National des Recherches Agricoles du Benin (INRAB)

Cameroon

Institute of Agricultural Research for Development (IRAD)

Cote d’Ivoire

Centre National de Recherche Agronomique (CNRA)

Centre Suisse de Recherches Scientifiques en Côte d’Ivoire (CSRS)

University of Abobo Adjame

Crops Research Institute (CRI)

Savanna Agric. Research Institute (SARI)

Kwame Nkrumah University of Science and Technology (KNUST)

Nigeria

National Root Crops Research Institute (NRCRI)

University of Ibadan

Ahmadu Bello University, Zaria

Institut Togolais des Recherches Agronomiques (ITRA)

CIRAD, France

Virginia State University, USA

A breeder

needs many

friends

Food, Income and Culture

Ethnobotany of yams – Ayensu & Coursey

Interactions of yam and man - Coursey

Sense of identity – Perrot

Yams in society - Degras

Co-speciation of yam and man

Yam festivals

A man’s crop?

Status

The future of yams - Manyong and Nokoe (2003)

Urbanization, Competition, Environmental degradation

Yam and man

DomesticationStakeholder analysis:

- 27 villages, Zou Province, Benin

- practised by experienced male yam growers

- in search of more productive varieties (60% of 80 respondents)

- selection based on similarity of leaves to known cultivars (58% of respondents)

Mignouna and Dansi. (2003) Genetic Resources and Crop Evolution 50: 519–528

Scarcelli et al. (2006) Molecular Ecology 15, 2421–2431

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Nigeria

Côte d'Ivoire

Production

Yam Area

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

millio

a) World

Nigeria

Côte d'Ivoire

Yam Yields in

West Africa

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006

Nigeria

Côte d'Ivoire

Yam supply (g)

per capita per

day 2005

100.00

200.00

300.00

400.00

500.00

600.00

700.00

800.00

900.00

Togo Nigeria Ghana Côte d'Ivoire Benin

Consumption (kcal/cap/day) 2003:

Togo (233), Nigeria (203), Ghana (314), CI (331), Benin (395)

Key challenges

• Planting materials

• Labour

• Germplasm

• Soil fertility

• Diseases and pests (including weeds)

• Post-harvest handling and processing

Yam Genetic

Improvement

High and stable yield of marketable tubers

(per unit of area, labour and time)

Pest and disease resistance

(nematodes, viruses, anthracnose, tuber rots)

Tuber characteristics(size, shape, branching, food quality, storability)

Suitability to cropping systems and tolerance to

abiotic stresses

(shoot morphology, nutrient responsiveness and

use efficiency, tolerance to mid- to late season

drought)

Genetic

Improvement

Objectives

Dioscorea rotundata

D. alata

D. cayenensis

D. dumetorum D. burkilliana

D. bulbifera D. esculenta

D. opposita D. japonica

D. trifida D. nummularia

D. abyssinica D. praehensilis

Focus on

Selected Food

•Whole tuber

•Tuber fragment

•Milking (double harvest)

•Multiple tuberisation

•Bulbil formation

Planting Materials

Good performance under no/limited staking

Early maturity and/or multiple tuber production

Suitability to short fallow systems

-Nutrient uptake, responsiveness & use

efficiency

-Pest resistance

Tuber morphology for easy harvesting

Long tuber dormancy

Labour Saving

Molecular characterization

(genotyping of core collection)

(reference collection)

Ploidy studies using DNA flow cytometry of Dioscorea alata and D. rotundata

AFLP marker diversity of Dioscorea alata

Development of genomic tools for improvement of yam

Characterization

of the core

collection

Figure 1. Genetic diversity tree of 342 yam accessions base

on SSR data using unweighted neighbour- joining analysis

D. alata (red)

D. bulbifera (purple)

D. cayenensis (yellow)

D. dumetorum (ash)

D. esculenta (blue)

D. rotundata (green)

Creating additional variation:

Interspecific crosses

Parents No. flowers poll. Fruit Set Seed Set

Female Male Number % Number %

D. rotundata D. rotundata 2491 965 38.74 3313 22.16

D. rotundata D. cayenensis 1581 154 9.74 9 0.1

D. rotundata D. alata 1663 6 0.36 9 0.09

D. alata D. alata 8120 1445 17.8 2577 5.28

D. alata D. cayenensis 89 0 0 0 0

D. alata D. rotundata 730 0 0 0 0

Examination of progenies generated from inter-specific crosses using an isozyme marker confirmed true hybrids

TDr 95/18544 TDc 98-136F1

F1TDr 95/19158 TDc 98-136

TDr 89/02475 TDc 98-136

TDr 85/18555 TDc 95-165

D. alata for reaction to yam anthracnose and virus diseases and their effect on yield

Anthracnose and virus diseases of D. alata: effects of yam genotype and planting date

Screening of Dioscorea alata for reactions to viruses

Reaction of Dioscorea rotundata to virus diseases in four agroecological zones

Impact of Yam mosaic virus genus Potyvirus on field performance of white yam

Pathogenic and genetic variability among Colletotrichum gloeosporioides isolates from different yam hosts in the agroecological zones in Nigeria

Evaluation:

Host plant

resistance

Anthracnose disease

Sources of resistance identified to selected isolates and

used but variability of pathogen is a continuing challenge

Abang et al. 2006. Journal of Phytopathology 154: 51-61

Sources of resistance identified and hybridized

Odu et al. 2006. Journal of Phytopathology 154: 716-724

Odu et al. 2006. Journal of Phytopathology 154: 688-693

Odu et al. 2004. Field Crops Research 89: 97-105.

Odu et al. 2004. Plant Pathology 53: 141-147

Viruses

Germplasm

delivery to

partners

Recipient No. of Genotypes

D. rotundata D. alata

AGIP NaOC, Nigeria 24 26

DDS, Nigeria 4 14

PNDRT, Cameroon 21 16

NRCRI, Nigeria 11

CARI, Liberia 57

AARC, Awassa, Ethiopia 30

INRAB, Benin 46 20

ITRA, Togo 16

NRCRI, Nigeria 84 7

INRAB, Benin 12 52

CNRA/CSRS 36 44

CRI, Ghana 17

SARI, Ghana 17

ITRA, Togo 26

Tubercules de TDa 98/01176 préconditionnés

en plein champ pour le stockage dans le

village de Kprakro(Dimbokro) 6 déc.2007

National Root Crops Research Institute, Nigeria:

Three new varieties of D. rotundata in 2001

Four new varieties of D. rotundata in 2003

Crops Research Institute, Ghana:

Three new varieties of D. rotundata in 2005

Need for advocacy for yam variety release

protocols

Varietal

releases

Nematodes

Necrotic spotsCracks & flaking of skin Dry rot

Damage caused by Scutellonema bradys

Galls & crazy rootsGalls

Damage caused by Meloidogyne spp.

Galls and rot

Resistance

identified in

Dioscorea

dumetorum

but not in

the two

dominant

species –

D. alata

and D.

rotundata

Insect pests of yam tubers

MealybugsScale insects

Tuber moth damageYam beetles

The challenge:

Pest build-up

Soil fertility and structure

Vesicular arbuscular mycorrhiza in the nutrition of yams

• Effects of arbuscular mycorrhizal inoculation and phosphorus application on yield and nutrient uptake of yams

• Effect of NPK fertilizer on the tuber yield, leaf nutrient concentrations and mycorrhizal colonization of white yam (Dioscorea rotundata)

Breeding for nutrient responsiveness

Sustainability

(sedentarization) of

yam production

Colonization (%) of roots of Dioscorea alata by VAM fungi at 4 sites

in Nigeria

Clone Site

Abuja Ibadan Onne Ubiaja Mean

TDa 85/00250 68.00 84.72 39.94 88.32 70.25

TDa 00/00064 78.23 45.09 61.06 88.84 68.31

TDa 00/00104 75.55 55.58 51.98 89.23 68.09

TDa 92-2 72.90 20.91 34.65 75.77 51.06

TDa 99/00395 44.49 45.69 34.78 77.29 50.56

TDa 02/00193 58.97 35.78 48.64 54.64 49.51

TDa 93-36 50.54 28.47 32.48 82.38 48.47

Mean (36 clones) 68.64 45.15 44.31 78.20 59.08

S.e.d: clone = 6.3, location = 2.1, clone x location = 12.6

CV% = 26.1

Colonization (%) of roots of Dioscorea rotundata at 4 sites in Nigeria

Clone Site

Abuja Ibadan Onne Ubiaja Mean

TDr 97/00588 85.42 78.89 58.38 81.23 75.98

TDr 89/02665 79.38 44.53 78.01 71.50 68.36

TDr 96/01799 79.03 47.67 77.33 69.00 68.26

TDr 96/00528 53.73 49.57 52.90 31.25 46.86

TDr 97/00903 62.38 47.53 1.12 69.78 45.20

TDr 97/00632 56.73 31.45 51.37 40.47 45.01

EHOBIA 33.18 30.53 28.83 44.25 34.20

Mean (for 34 clones) 67.99 43.04 57.11 59.73 56.97

S.e.d: clones = 6.54; Location = 2.24; Clone x location = 13.07

CV (%) = 28.1

AM Fungi

0 0.05 0.5 5

P concentrations (mg P kg-1

mycorrhiza

no mycorrhiza

Tuber yield of TDr 97/00903 as affected by AM

fungal inoculation and P application.

Tuber yields of

eleven genotypes

of Dioscorea

rotundata at

different

application rates

of NPK 15-15-15

Dioscorea rotundata genotypes

Food and nutritional quality

Description (target attributes for fresh tuber and

flour markets)

Intrinsic and exogenous influences

Effect of tuber harvest time and storage period on

the pasting properties of yam starch

Influence of time of harvest on the yield and

sensory attributes of white yam

Influence of environment and processing on tuber

micronutrient content

Food quality and

end-use suitability

Screening for tuber contents of total carotenoids, iron, zinc, ascorbic acid, and phytic acid

Variation in retention of total carotenoids, Fe and Zn in Dioscorea cayenensis food products

Influence of environment and genotype x environment interactions on tuber contents of iron and zinc

Total carotenoids (in µg/g fwb)

Dioscorea cayenensis (82 accessions)

Range: 1.25 – 5.12

Mean: 2.72 + 0.80

D. dumetorum

Two accessions with values of 22.29 and 26.60 µg/g

Tuber Density of

Micronutrients

Tuber content of ascorbic acid (in mg/100g fwb) :

D. rotundata (325 accessions)

Range: 3.56 – 16.87

Mean: 8.3 + 2.26

D. cayenensis (79 accessions)

Range: 4.19 – 11.34

Mean: 7.85 + 1.29

D. dumetorum (31 accessions)

Range: 15.42 – 39.43

Mean: 25.83 + 6.29

Tuber Density of

Micronutrients

Iron Zinc Ascorbic acid

SOV DF MS % SS MS % SS MS % SS

Total 371 4.90 3.94 2.46

TRT 123 9.74*** 65.8 9.02*** 75.8 4.76*** 64.2

GEN 30 13.76*** 34.4 23.08***62.4 5.68*** 29.2

ENV 3 115.94***29.0 45.60***12.3 61.40*** 31.5

G x E 90 4.86*** 36.5 3.10*** 25.2 2.56*** 39.4

Tuber nutrient contents of 31 genotypes of D. rotundata evaluated

at 4 sites over two years in Nigeria

Retention (%) of micronutrients in products from

15 genotypes of Dioscorea cayenensis

Boiled yam Pounded yam Flour

Carot. 31-97 9-97 11-75

(69.6) (48.6) (43.2)

Iron 56-99 66-99 18-44

(77.2) (80.3) (29.4)

Zinc 70-96 62-97 13-32

(85.4) (83.6) (22.6)

Micronutrients

Descriptive statistics for functional (pasting) characteristics of 33 genotypes

of D. rotundata grown at Abuja, Nigeria

viscosity

Breakdown

viscosity

Setback

viscosity

Peak time

(Min.)

Pasting

temp.( C)

Mean 209 38 247 76 6 84

SE 11.7 6.6 12.86 7.66 0.11 0.17

Min. 69 4 97 29 5 82

Max. 338 147 397 209 7 86

Pr. > F ** * * * * * * * ns

* *, *Significant at P<=0.01, and at P=0.05 respectively; ns=not significant

P>=0.05

100.00

150.00

200.00

250.00

300.00

350.00

k Visc.

Breakd

Final visc.

ting tim

ting temp.

D. alata

D. rotundata

Evaluation of Dioscorea alata varieties for

making pounded yam

Mean pasting

properties of D.

alata and control

Mean scores for pounded yam from D. alata

Variety Color Smoo. Cons. Elast. Stick. Hard.

Mean 4.66 4.22 3.97 3.56 4.22 4.66

SE 0.27 0.11 0.14 0.14 0.14 0.12

P level *** *** *** ** ** ***

Scale of 1 to 9, where 1= extremely inferior, 2= much inferior, 3= moderately

inferior, 4 = slightly inferior, 5= no difference, 6= slightly better, 7=moderately

better, 8=much better, 9= extremely better

Keeping yam a

part of man• Is it possible? – yes

• Is it important? – yes!

much!!

Keeping the yam 'a part of man

Technology

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