Keeping the yam 'a part of man'

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

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


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


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

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


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


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


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)


Yam Genetic Key challenges
Improvement
• Planting materials
• Labour
• Germplasm
• Soil fertility
• Diseases and pests (including weeds)
• Post-harvest handling and processing


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)


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


Planting Materials
•Whole tuber
•Tuber fragment
•Milking (double harvest)
•Multiple tuberisation

•Bulbil formation


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


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


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


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


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


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


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


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


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


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


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.

Insect pests of yam tubers

Mealybugs
Scale insects

Yam beetles Tuber moth damage


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


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

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.

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


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


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


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


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


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)


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

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
0.00
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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!


Thank
you
very
much!!


Keeping the yam 'a part of man'

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