Progress and Achievements in the Genetic Enhancement and Breeding of Cassava for Sub-Saharan Africa

Progress and Achievements in the Genetic
Enhancement and Breeding of Cassava
for Sub-Saharan Africa
2005 -2007

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

Five main roles
• Famine reserve crop
• Rural food staple
• Cash crop for urban consumption
• Industrial raw material
Food and
• Earner of foreign exchange Beverage

Paper Mono-
sodium
glutamate
Wood CASSAVA
Oil
drilling
Animal
Feed Textile
Ethanol

Major constraints/traits addressed:
Biotic: Cassava mosaic disease (strains & variants), Cassava
brown streak disease, bacterial blight, root rots,
anthracnose disease, green mite and root and tuber scale.
Abiotic: Soil acidity, soil fertility, drought.
Nutritional: Root dry matter/starch content, mealiness (cooking quality),
cyanide content, and beta-carotene and protein contents.


Others:

Postharvest physiological deterioration (PPD).

New Opportunities:
• Industrial and diversified uses (e.g. high root starch content,
starch quality such as waxy starch, and high sugar content for
bio-ethanol production)

• Livestock feed (e.g. high root and foliage yield and protein
content).


Breeding objectives for the development of
new cassava varieties in SSA

1. High root dry matter and starch yield (per unit area and time)
2. Improved quality and nutrition (e.g., high starch content and quality,
low cyanogenic potential (CNP), mealiness, reduced or delayed
postharvest deterioration, high beta-carotene content, high protein
content, foliage yield, and quality)
3. Disease resistance (CMD, CBSD, CBB, CAD, root rots)
4. Pest resistance (CGM, ARTS, and whiteflies)
5. Good plant type
6. Good adaptation to major agroeecologies and production systems

Geographical Focus
 Humid forest, moist savanna, dry savanna and midaltitude
agroecological zones.

Major Linkages

NARS
• 19 NARS in West and Central Africa
• *EARRNET (9 NARS in East Africa)
• SARRNET (12 NARS in Southern Africa)
• EMBRAPA and IAC in Brazil.
• *DR Congo and Tanzania common to both EARRNET and SARRNET


ARIS:
 University of Copenhagen, German Collection of Microorganisms and Cell
Cultures (DSMZ), Plant Virus Division, Braunschweig, Germany),
 Ohio State University
 Donald Danforth Plant Science Center (Mo)
 Swiss Federal Institute of Technology, Zurich (ETH),
 Joint FAO/IAEA Agriculture and Biotechnology Laboratory of the
International Atomic Energy Agency, Austria
 HarvestPlus Challenge Program (Consortium of universities and research
institutions worldwide)
 BioCassava Plus of the Grand Challenges in Global Health initiative
(Consortium of universities and research institutions worldwide)
 Generation Challenge Program (Consortium of universities and research
institutions worldwide).


Development and improvement of cassava source populations

Basic Strategy of Cyclical Selection of Source Population

Develop a Source Population

Inter-cross Evaluate
Superior Progeny Progeny

Select Superior Progeny


Ploidy Manipulation

Unilateral and Bilateral Sexual Polyploidization
(2x X 2x, 2x X 4x, 4x X 2x, 4x X 4x crosses)

Somatic Polyploidization
Sexual Colchicine (0.1%) Sol’n Somatic Sexual
Diploids (2x) Tetraploids (4x) X Tetraploids (4x)

Improved Diploids X Improved Tetraploids
(2x) (4x)

Productive Triploids
(3x)


Germplasm Introduction (further broaden the genetic base)

CIAT (2003): 38 clones [Latin American landraces (Brazil, Colombia, and Peru),
South-east Asian landraces (Thailand) targeting whitefly resistance, high starch
content, good eating quality, and agroecological adaptation to the lowland humid,
acid savanna, and midaltitude agroecologies.

Agronomic Institute of Campinas, Sao Paulo, Brazil, Brazil (2005): Industrial
varieties of six elite lines and landraces (high starch and cold tolerant) including
yellow-fleshed lines (IAC 576-70, IAC-12,IAC-14, FECULA-3, ESPETO-7, and
BRANCA DE SANTA CATARINA).
2006: Five (IAC 13, IAC 90, IAC 15, Fecula Branca, Fibra, and Olho Junto).

CIAT (2007): half-sib seeds from the backcross generation of the cultivated
cassava x Manihot walkerae for delayed onset of postharvest physiological
deterioration
Latin Amerian lines (breeding lines and land races) with higher storage root
protein and yellow fleshed roots
Five genotypes and 50 tissue culture derived plantlet from seeds of the first
backross generation of selected interspecific progenies for high protein.

Swiss Federal Institute of Technology, Zurich (2007): Some cassava lines for high
starch content from Asia (KU50, MThai 25Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
International Institute of and MThai 27).

Acquisition of African adapted germplasm
(2004)
42 African varieties were introduced from South Africa as virus-
tested in vitro plantlets in 2004 to enrich IITA breeding population
with African adapted gene pools

Tanzania Landraces and improved varieties 18
Malawi Landraces and improved varieties 14
Zambia Landraces and improved varieties 11

Acquisition of micronutrient rich (beta carotene) seed
populations
CIAT 2005: = 207 families (4754 seeds)
EMBRAPA, Brazil (through CIAT) 2005: Micronutrient rich
(betacarotene)=59 families (8074 seeds)

• Evaluation, introgression into breeding pools and selection

Major Disease/Pest Constraints of Cassava

Mosaic Disease Bacterial Blight Anthracnose Root Rots

Brown Streak Disease

Mealybug Green Mite African Root and Tuber Scale


Host-plant Resistance Breeding

CMD-resistant CMD-susceptible Multiple resistance to diseases and pests

 Improved multiple disease and pest resistant clones showing high levels of
resistance to CMD
 While incorporating resistance to diseases and pests, popular features of
African landraces are maintained to aid adoption – Institut international d’agriculture tropicale – www.iita.org
International Institute of Tropical Agriculture

Relative Variety
TME 419
FWS
12.14
DWF Rel. imp
3.58 27.40
improvement in 92/0326 15.14 3.63 29.18

forage yield of 97/4779
92/0057
14.66
18.78
3.7 31.67
3.82 35.94
improved varieties 98/0581 16.4 4.13 46.98

over the checks M98/0040
99/6012
15.09
15
5.18 84.34
8.51 202.85
30572 16.41 2.46 0.00
• Among the 43 tested clones seven 4(2)1425 13.63 2.27 0.00
produced more forage compared to the 82/00058 18.47 3.71 0.00
control 96/1632 14.93 0.88 -68.68
• They include clones 99/6012 (203%), 98/2226 15.47 1.13 -59.79
M98/0040 (84%), 98/0581 (47%), 92/0057 97/0211 9.51 1.48 -47.33
(36%), 97/4779 (32%), 92/0326 (29%) and 96/1569 7.21 1.68 -40.21
TME 419 (27%) 97/3200 14.63 1.74 -38.08
• Cassava clone 99/6012 gave an 99/2123 19.36 1.77 -37.01
outstanding performance producing more 99/3073 16.46 1.77 -37.01
than thrice the forage yield obtainable in Mean 15.26 2.74
the three checks CV 18 45
SE 0.42 0.19
FWS = Fresh weight shoot (t/ha); DWF = Dry weight forage (t/ha); Rel. imp = Relative improvement
based on DWF (%) International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

Mean concentration of micronutrient
@ 6, 9, &12MAP
β-carotene (μg/g) Iron Zinc (mg/kg)
(mg/kg)
MAP 6 9 12 9 12 9 12
Mean 0.33 3.08 2.09 9.36 6.52 9.04 7.93
SE 0.25 0.88 0.65 0.8 0.78 0.57 0.54

β-carotene 6 & 9 MAP DF =24 T value = -7.96 p <.0001
β-carotene 6 & 12 MAP DF =24 T value = -7.34 p <.0001
β-carotene 9 & 12 MAP DF =24 T value = 2.53 p = .0182
Iron 9 & 12 MAP DF =24 T value = 5.24 p <.0001
Zinc 9 & 12 MAP DF =24 T value = 2.68 p =.0132


Screening for Carotenoids, Fe & Zn

Carotenoids (fresh wt basis)
Year Total Total Screening method Deep Light Min Max
No. No. yellow yellow TC TC
families plants selected selected
2004/05 476 16,832 Color chart, 24 379 - 10.1
spectrophotometric μg/g †
2005/06 982* 19,644 Color chart, 895 1386 2.8 11.9
spectrophotometric μg/g μg/g
2006/07 490 8743 Color chart, 667 158 1.23 14.81
spectrophotometric μg/g μg/g
2007/08 638 28,865 Color chart, 1548 >500 1.56 13.27
spectrophotometric
*Comprised of 133 families from CIAT, 59 from Brazil, and 790 local crosses from IITA Ibadan ; †obtainedfrom 2005 clonal evaluation.


Fe and Zn (dry wt basis)

Year No. No. Screening Max Max
families plants method Fe Zn

2004/05 476 16,832 - - -
2005/06 982 19,644 ICPAES - -

2006/07 490 8743 ICPAES 56.81 73.78
mg/kg mg/kg
2007/08 638 28,865 ICPAES


GxE
GLM :
G x E interactions
components for Fe
& Zn generally ns

AMMI:
•High G –TC
•High E & G x E–
Zn, Fe
•G (Fe) ~ G( Zn)


G x E: carotenoid concentration

 Carotenoid
concentration is
a stable trait

 Single location
selection reliable


Agronomic characteristics, pest reactions of
promising micronutrient-rich clones

Clone CMD CGM Yield DM Carotene Fe Zn
(t/ha) (%) (µg/g) mg/kg mg/kg

05/1601 1.0 2.0 36.5 38.9 9.4 10.7 12.2
05/1600 3.2 2.5 34.5 29.0 6.5 9.0 12.0
05/1570 1.0 2.0 33.3 41.9 2.4 7.9 12.3
05/0327 1.0 4.5 28.4 37.8 6.2 6.5 14.3
05/1862 1.2 2.5 27.1 39.3 4.5 7.7 10.3
05/0311 1.0 2.5 25.7 40.9 5.5 7.2 8.3
05/0099 1.0 2.0 25.1 38.9 5.8 7.0 8.9
05/1654 1.0 3.0 23.0 34.9 6.9 17.4 15.1
05/0476 1.0 3.0 19.7 40.3 4.0 8.9 10.5
05/1652 1.0 2.5 19.5 31.3 8.3 9.4 13.8


G x E: YLD, DM, DY

G effect highest for DM
E effect highest for YLD
G x E*** for all traits


Percentage nutrient retention during traditional
processing of yellow-fleshed cassava storage roots

120

Percent true retention
100

80
01/1371
60 01/1235
94/0006
40

20

0
Sun-dried Raw fufu Cooked Boiled gari
chips fufu cassava
Processed product

Highest nutrient retention in boiled roots
Maziya-Dixon et. al., 2007.
Submitted to LWT-J. Food Science

Carotenoid concentration at different steps of
processing cassava storage roots to gari

18
16

Total carotenoid(ug/g)
14
12
TMS94/0006
10
TMS01/1235
8
TMS01/1371
6
4
2
0
Peeled raw Grated Grated and Fermented Roasted gari
cassava cassava fermented pressed granules
roots mash mash mash/cake

Maziya-Dixon et al., 2007. Int. J. Food Science and Technology.

Carotenoids profile of 22 yellow-fleshed
cassava genotypes

90% of the carotenoids in cassava is β-carotene
> 50% of the carotenoids in cassava is Trans- β-carotene

Polyploid breeding for enhanced
micronutrient content
 Tetraploidy was also artificially
induced (0.1% solution of
cholchicine) in over 20 promising
yellow-fleshed diploid cassava
clones.

 4x versus 2x counterparts

 Effect of polyploidization on
micronutrient content evaluated

(carotene 4x>carotene2x)

 Tetraploid x diploid crosses for
more productive triploids

Tetraploids (mean = 5.41 µg/g) had significantly higher content of total carotene
than the diploids (mean=4.65 µg/g).
The carotene content of the tetraploids ranged from 0.69 µg/g to 10.05 µg/g; that of
the diploids ranged from 0.44 to 8.39 µg/g.
The mean dry matter content of the tetraploids (33.45%) was significantly lower
than that of the diploids (36.78%), though several of the tetraploid clones had higher
dry matter content of over 36%.
The dry matter content of the diploids ranged from 27.19% to 42.49%; that of the
tetraploids ranged from 27.82% to 37.91%.
The clone x ploidy level interaction for both total carotenoid and dry matter content
was also significant.


Descriptive statistics for chemical composition of cassava leaves
(DWB) of 630 genotypes
Total Starch Protein Dry Fat Tannin
sugars (%) (%) Matter (%) (%) (mg/100g)
(%)

Mean 8.49 16.17 30.12 26.37 6.05 8.85

SE 0.16 0.17 0.08 0.11 0.04 0.08

Min. 2.4 4.0 25.6 18.0 1.3 4.0

Max. 62.8 35.3 38.0 53.0 14.9 17.2

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

* * *, * *, *Significant at P<=0.001, P<=0.01, and P<=0.05 respectively; ns=not significant
P>=0.05 International Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org

Descriptive statistics for chemical composition of cassava storage roots
(DWB) of 637 genotypes
CNP1 Total Starch Protein Ash Amylose Dry
sugars (%) (%) (%) (%) matter
(%) (%)

Mean 14.6 5.83 60.49 2.26 3.65 19.41 24.81

SE 0.26 0.11 0.37 0.02 0.03 0.08 0.17

Min. 3.9 0.6 20.1 0.7 2.1 11.6 11.1

Max. 39.0. 20.0 93.0 4.8 6.1 29.2 42.8

Pr. > F *** ns ns *** ** ** ***
* * *, * *, *Significant at P<=0.001, P<=0.01, and P<=0.05 respectively; ns=not
significant P>=0.05; 1= mg/100 g HCN Equivalent

Descriptive statistics for functional (pasting) characteristics of cassava
storage roots of 637 genotypes
Peak Breakdown Final Setback Peak time Pasting
viscosity viscosity viscosity viscosity (Min.) temp.( C)

Mean 196 115 112 32 4.63 82

SE 2.22 1.45 2.14 0.69 0.02 0.62

Min. 52 26 2.5 0.2 1.9 50

Max. 633 479 265 106 7.0 89

Pr. > F * *** ns ns ns ns
* * *, *Significant at P<=0.001, and at P<=0.05 respectively; ns=not significant

There is a relationship between physical, chemical, and functional
What we learned characteristics of the raw material and the final product, therefore
we need to target our technologies

Processing resulted in reduction of provitamin A carotenoid
retention and that this depended on the genotype and processing
method.

There is a potential for improving micronutrient status of vulnerable
groups


Shift in nutrient levels with breeding and
selection for root nutritional quality

2003/2004 2006/2007 % increase
β-carotene 4.8μg/g 13μg/g >150
Iron 10.3mg/kg >35mg/kg >200
Zinc 10.3mg/kg > 60mg/kg >400
Protein 1-4% >25% >400


Deployment of in vitro germplasm

Virus-free certified tissue culture plantlets

HS seed families of beta-caroten enriched parental
clones
Country Seed families No. of seeds
Guinea 71 10,100
Congo DR 30 10,000
Uganda 64 10,100
Kenya 23 23,000
Malawi 24 24,000
Angola 23 23,000
Mozambique 23 23,000
Sierra Leone 23 46,000
Ghana 17 18,100

Some official varietal releases of improved cassava by
NARS between 2004 and 2007

Year Country Variety name
2004 DR Congo TMS 95/0211 (Disanka), TMS 95/0528 (Mvuazi), TMS 96/0160
(Nsansi), MV 99/0395 (Butamu), MV 99/0038 (Zizila), MM
96/0287(Liyayi), and MM 96/7204 (Namale)
2004 Swaziland Clones 160, 48 & 65, TMS 92/0326, and Rushinga
2005 Ghana: TMS 97/4962 (Abglifa), TMS 97/4414 (Bankyehemaa), TMS
97/3982 (Esam bankye), and TMS 97/4489 (Doku duade)
2005 Nigeria TMS 97/2205, TMS 98/0505, TMS 98/0510, TMS 98/0581, and
TME 419.
2006 Nigeria TMS 92/0326, TMS 92/0057, TMS 96/1632, TMS 98/0002, and NR
87184.
2006 Sierra Leone TMS 92/0057 (SLICASS 6)
2007 Benin TMS 91/02322 (Manina), TMS 92B/00061(Ina–H), TMS
92/0427(Ina – Premier), and TMS 92/0067 (MR-67)

Nouvelles variétés en diffusion
IITA No DRC name CMD Yield (t/ha)

96/0160 Nsansi 1 22.8

95/0528 Mvuazi 1 21.6

MV99/0038 Zizila 1 21.5

95/0211 Disanka 1 20.7

MV99/0395 Butamu 1 16.8

RAV RAV 3 18.6

Boma Boma 4 9.46

CMD score of 1-5 whereInternational Institute of Tropical Agriculture – Institut international d’agriculture tropicale – www.iita.org
1=no symptoms and 5 =severe damage

Capacity building and technology dissemination

Degree and non-degree training

Training of Trainers

Demand-driven processing workshops


Summary of the progress and
achievements

 Seven additional sources of resistance to CMD and other prelent disease and
pest identified in landraces collected from West Africa and used to pyramid and
diversify and heighten resistance for durable control.
 Significant advances in broadening the genetic base of cassava in Africa
and producing several improved cassava genetic stocks and breeding
materials which combines enhanced CMD resistance with improved post
harvest qualities, multiple pest/disease resistance, wide agrocological
adaptation and greatly improved yield potential (which may also be used
directly as varieties) and shared with NARS.
 Massive use of African landraces and Latin America germplasm
(increased yields in many African locations by 50-100% even without the
use of fertilizer).


 In vitro virus-tested plantlets and seed populations of broad-based and special
trait source breeding populations exchanged with National programs
 Increasing number of improved varieties released by NARS in major cassava
producing countries of the cassava belt as a result of broadening the genetic base
of cassava at IITA with Latin American germplasm and the increased use of
African landraces in the breeding program.
 Enhanced NARS research capacity in cassava through training under IITA co-
supervision for MSc, PhD, and/or group training, and extensive collaboration
throughout SSA.


Public Awareness and Advocacy

Minister of Agriculture and senior
officials of FMARD–IITA (10 Feb)

Dignitaries at the high table during the
VP, FGN on a visit to IITA book launch

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


Mounds for ceremonial yam Mounds in savanna zone

Staking in forest zone Staking in savanna zone

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


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


Example of delivery of new clones of D.
rotundata to partners in a year
Country Partner No. of clones
Benin INRAB 234
Cote d’Ivoire CSRS 80
Ghana CRI & WASDU 169
Nigeria NRCRI 104
Togo ITRA 166


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


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


Internal Brown Spot


Opportunities


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

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

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

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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

Benin
Institut National des Recherches Agricoles du Benin (INRAB)
Centre régional de Nutrition et d’Alimentation Appliquées (CERNA)

Key NARS Cameroon
University of Dschang
Partners Institute of Agricultural Research for Development (IRAD)
The University of Buea
AGROCOM

Cote d’Ivoire
Centre National de Recherche Agronomique (CNRA)
Centre Suisse de Recherches Scientifiques en Côte d’Ivoire (CSRS)
University of Abobo Adjame

Ghana
Crops Research Institute (CRI)
Savanna Agric. Research Institute (SARI)
Kwame Nkrumah University of Science and Technology (KNUST)
University For Development Studies

Nigeria
National Root Crops Research Institute (NRCRI)
Bowen University
Ladoke Akintola University of Technology (LAUTECH)

Togo
Institut Togolais des Recherches Agronomiques (ITRA)

Other Research • CIRAD, France
Partners • Virginia State University, USA
• University of Ibadan, Nigeria
• Federal University of Technology, Nigeria
• Ahmadu Bello University, Zaria, Nigeria
• University of Nigeria, Nigeria
• Ladoke Akintola University of Technology,
Nigeria

Graduate Training 2007
• 10 students conducting research towards PhD
degrees


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