This document discusses yam breeding and genetic improvement efforts. It summarizes:
1) Yam is an important crop for food security and culture in West Africa. Breeding efforts focus on popular species like D. rotundata and D. alata.
2) The goals of yam breeding include developing varieties with high yields, pest and disease resistance, good tuber characteristics, and abiotic stress tolerance.
3) Various research institutions in West Africa are conducting yam characterization, evaluation, crossing, and distribution of improved varieties to farmers. New varieties have been released with traits like virus resistance.
4) Challenges include pests, diseases, declining soil fertility, and lack of
1. Keeping the yam ‘a part of man’
- a breeder’s contribution
Robert Asiedu
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
2. Benin
Institut National des Recherches Agricoles du Benin (INRAB)
Cameroon
A breeder Institute of Agricultural Research for Development (IRAD)
Cote d’Ivoire
needs many Centre National de Recherche Agronomique (CNRA)
Centre Suisse de Recherches Scientifiques en Côte d’Ivoire (CSRS)
friends University of Abobo Adjame
Ghana
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
Togo
Institut Togolais des Recherches Agronomiques (ITRA)
CIRAD, France
Virginia State University, USA
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
3. Yam and man 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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
4. Domestication
Stakeholder 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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
5. Yam
Production
60
Production (million tons) 50
World
40
Togo
Nigeria
30
Ghana
Côte d'Ivoire
20
Benin
10
0
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Year
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
6. Yam Area
5
4.5
4
3.5 World
Area (million ha)
3 Togo
Nigeria
2.5
Ghana
2 Côte d'Ivoire
1.5 Benin
1
0.5
0
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Year
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
7. Yam Yields in
West Africa
16
14
12 World
Yield (tons/ha)
10 Togo
Nigeria
8
Ghana
6 Côte d'Ivoire
4 Benin
2
0
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006
Year
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
8. Yam supply (g)
per capita per
day 2005 900.00
800.00
Yam supply (g) per capita per day
700.00
600.00
500.00
400.00
300.00
200.00
100.00
0.00
Togo Nigeria Ghana Côte d'Ivoire Benin
Consumption (kcal/cap/day) 2003:
Togo (233), Nigeria (203), Ghana (314), CI (331), Benin (395)
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
9. Yam Genetic Key challenges
Improvement
• Planting materials
• Labour
• Germplasm
• Soil fertility
• Diseases and pests (including weeds)
• Post-harvest handling and processing
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
10. High and stable yield of marketable tubers
Genetic (per unit of area, labour and time)
Improvement
Pest and disease resistance
Objectives (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)
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
11. Focus on Dioscorea rotundata
Selected Food D. alata
Yams D. cayenensis
D. dumetorum D. burkilliana
D. bulbifera D. esculenta
D. opposita D. japonica
D. trifida D. nummularia
D. abyssinica D. praehensilis
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
12. Planting Materials
•Whole tuber
•Tuber fragment
•Milking (double harvest)
•Multiple tuberisation
•Bulbil formation
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13. Labour Saving 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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
14. Characterization 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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
15. Characterization
of the core
collection
D. alata (red)
D. bulbifera (purple)
D. cayenensis (yellow)
D. dumetorum (ash)
D. esculenta (blue)
D. rotundata (green)
Figure 1. Genetic diversity tree of 342 yam accessions base
on SSR data using unweighted neighbour- joining analysis
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
16. 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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
17. a b
TDr 95/19158 F1 TDc 98-136
TDr 95/18544 F1 TDc 98-136
C d
+
TDr 85/18555 TDc 95-165 TDr 89/02475 TDc 98-136
F1 F1
Examination of progenies generated from inter-specific crosses using an isozyme marker confirmed true hybrids
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
18. D. alata for reaction to yam anthracnose and virus diseases
Evaluation: and their effect on yield
Host plant
resistance 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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
19. 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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
20. Viruses
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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
21. Recipient No. of Genotypes
D. rotundata D. alata
2008
Germplasm AGIP NaOC, Nigeria 24 26
delivery to DDS, Nigeria 4 14
PNDRT, Cameroon 21 16
partners
NRCRI, Nigeria 11
2007
CARI, Liberia 57
AARC, Awassa, Ethiopia 30
INRAB, Benin 46 20
ITRA, Togo 16
2006
NRCRI, Nigeria 84 7
INRAB, Benin 12 52
CNRA/CSRS 36 44
CRI, Ghana 17
Tubercules de TDa 98/01176 préconditionnés SARI, Ghana 17
en plein champ pour le stockage dans le
village de Kprakro(Dimbokro) 6 déc.2007 ITRA, Togo 26
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
22. Varietal National Root Crops Research Institute, Nigeria:
Three new varieties of D. rotundata in 2001
releases
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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
23. Nematodes
Resistance
identified in
Dioscorea
dumetorum
but not in Cracks & flaking of skin Necrotic spots Dry rot
the two
Damage caused by Scutellonema bradys
dominant
species –
D. alata
and D.
rotundata
Galls Galls & crazy roots Galls and rot
Damage caused by Meloidogyne spp.
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
24. Insect pests of yam tubers
Mealybugs
Scale insects
Yam beetles Tuber moth damage
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
25. The challenge:
Sustainability Pest build-up
(sedentarization) of Soil fertility and structure
yam production
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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
26. 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
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27. 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 International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
28. 200
AM Fungi 180
mycorrhiza
no mycorrhiza
160
140
Tuber weight (kg)
120
100
80
60
40
20
0
0 0.05 0.5 5
P concentrations (mg P kg-1soil)
Tuber yield of TDr 97/00903 as affected by AM
fungal inoculation and P application.
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
29. 16.00
14.00
Tuber yields of 12.00
eleven genotypes
of Dioscorea 10.00
Tuber yield (t/ha)
0
rotundata at 200
8.00
different 400
600
application rates 6.00
of NPK 15-15-15
4.00
2.00
0.00
93-31
93-32
01/00504
96/00629
97/00205
97/00609
97/00632
97/00777
97/00793
97/00903
97/01818
Dioscorea rotundata genotypes
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
30. Food quality and Food and nutritional quality
end-use suitability 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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
31. Tuber Density of Screening for tuber contents of total carotenoids, iron,
zinc, ascorbic acid, and phytic acid
Micronutrients
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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
32. Tuber Density of Tuber content of ascorbic acid (in mg/100g fwb) :
Micronutrients
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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
33. Tuber nutrient contents of 31 genotypes of D. rotundata evaluated
at 4 sites over two years in Nigeria
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
GxE 90 4.86*** 36.5 3.10*** 25.2 2.56*** 39.4
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
34. Micronutrients 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)
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35. Descriptive statistics for functional (pasting) characteristics of 33 genotypes
of D. rotundata grown at Abuja, Nigeria
Peak Breakdown Final Setback Peak time Pasting
viscosity viscosity viscosity viscosity (Min.) 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 International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
36. Evaluation of Dioscorea alata varieties for
making pounded yam
Mean pasting 350.00
properties of D. 300.00
alata and control 250.00
200.00 D. alata
150.00 D. rotundata
100.00
50.00
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International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
37. 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
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
38. Keeping yam a
part of man
• Is it possible? – yes
• Is it important? – yes!
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
39. Thank
you
very
much!!
International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org