A Combining Ability Analysis of Cassava Genotypes to Yield and Cassava Mosaic Disease E.Y. Parkes, M. Fregene, A.G.O. Dixon, H. Ceballos, B.B. Peprah, P. Illona, P.A. Kulakow and M.T. Labuschagne presented at the GCP 21-!! Meeting, Speke Hotel Kampala at Uganda from 18th -22nd June 2012

Introduction Cassava supports over 800 million people in sub-Saharan Africa. Grown in 39 countries 80% of the production is from West Africa Ghana is the 3rd highest producer 10 million tons/year, thrives in adverse conditions Ranks first in area under cultivation and utilization .Over 70% of the resource poor farmers produce cassava Uses Food (‘gari’, ‘fufu’ etc) ,Feed for animals emerging industrial uses (starch for plywood, textiles, pharmaceuticals and ethanol production)

Materials and method Objective To determine the relative importance of general (GCA) and specific (SCA) combining ability among cassava genotypes diallel mating scheme of 7 (non-reciprocal) cassava genotypes Design: Randomised Complete Block (7 progenitors and 21 F1 progenies) ,3 replications Locations: (Ejura and Fumesua) for two seasons

Soil and climatic conditions of locations Research site Soil series Soil type Fumesua Bomso-Asuansi series (ferric acrisol) Sandy loam top soil over sandy clay Ejura Amantin series Sandy loam top soil Research site Eco-zone Rainfall (mm) Months of rainfall Temperature (oC) Fumesua Forest zone 1460-1750 Bimodal April-July Sep-Nov 20-34 Ejura Forest-transition zone 1300-1400 21-34

Source of parents for the study Accra Kumasi Wenchi 80Km UPPER EAST REGION UPPER WEST REGION NORTHERN REGION BRONG AHAFO REGION ASANTE REGION GREATER ACCRA CENTRAL WESTERN VOLTA EASTERN 320 landraces were collected from 73 villages in Ghana Each farmer contributed 2-5 cassava varieties DNA extraction done for all samples 36 SSR markers were used to analyze the 320 samples on PAGE

Crosses of 7 parents Dabodabo Debor Agric Lagos Tuaka Afebankye Kwasea Fig.8

Why diallel? The diallel mating design has been specifically designed to investigate the combining ability of parents and to identify superior parents for use in hybrid and cultivar development Diallel mating designs permit the estimation of the magnitude of additive and non additive components of the heritable variance (Griffing 1956; Mather and Jinks 1977).

Why diallel? Obtain information on the value of the progenitors assess the gene action involved in the various characters thereby develop appropriate selection procedures understand heterotic patterns of progenies at an early stage of hybridisation programmes (Dikerson 1969; Le Gouis et al. 2002; Egesel et al. 2003)

SCA is where certain hybrid combinations do relatively better or worse than would be expected on the basis of the average of the performance of the lines involved. It is the deviation to a greater or lesser extent from the sum of GCA of the parents. SCA consist of dominance and all types of epistatic variances and is regarded as estimates of effects of non-additive gene actions (Falconer and Mackay 1996).

Table1. Estimates of SCA effects for yield and CMD resistance of cassava progenies in the forest zone Crosses/F1 progenies Fryld Rootno Dryld DM CMD Dabodabo x Debor 0.33 -1.73** 0.06 -0.58 -0.11 Dabodabo x Agric -0.80* -0.26 -2.26 -0.46 0.08 Dabodabo x Lagos -0.21 -0.06 -0.04 0.28 Dabodabo x Tuaka 0.47 -0.02 0.07 -0.63 -0.12 Dabodabo x Afebankye -0.22 1.38* 0.46 -0.07 Dabodabo x Kwasea 0.43 0.68 0.16 0.93* 0.26 Debor x Agric 0.09 Debor x Lagos 0.11 0.04 -0.05 Debor x Tuaka -0.49 1.08 -0.08 1.08* Debor x Afebankye -0.17 -0.31 -0.29 Debor x Kwasea 0.97 -0.32

Table1. Estimates of SCA effects for yield and CMD resistance of cassava progenies in the forest zone (cont) Crosses/F1 progenies Fyld Rootno Dyld DM CMD Agric x Lagos 0.39 1.03 0.14 0.52 0.09 Agric x Tuaka 0.32 0.04 0.10 -0.18 -0.09 Agric x Afebankye -0.19 -0.48 -0.04 -0.77 0.15 Agric x Kwase -0.001 -0.27 -0.13 Lagos x Tuaka -0.23 -0.95 -0.10 Lagos x Afebankye 0.37 0.12 0.08 -0.03 Lagos x Kwasea -0.44 -0.12 Tuaka x Afebankye 0.17 0.008 0.31 -0.14 Tuaka x Kwasea -0.11 -0.33 -0.009 Afebankye x Kwasea 0.18 -0.88 0.05 -0.26 0.16 Rootno=average root number per plant, Fyld=fresh root yield, Dyld=Dry yield, DM=Dry matter content, SCA=specific combining ability * P≤0.05, ** P≤0.01

Table2. Estimates of GCA effects for yield and CMD resistance of cassava progenies in the forest zone Parents Fyld Rootno Dyld DM CMD Dabodabo -0.11 0.27 -0.02 0.51* -0.12 Debor -0.06 -0.60* -0.04 -0.34 0.16* Agric -0.26 -0.92** -0.09 -0.10 0.18** Lagos -0.07 -0.20 -0.01 Tuaka 0.35 0.52 0.08 -0.40 -0.15* Afebankye 0.29 0.004 0.20 -0.03 Kwasea -0.16 0.63 0.07 -0.36*

Table 3. Mean squares for GCA and SCA for CMD, yield and yield components of cassava genotypes for the forest ecological zone 2008/2009 Source Df Rootno Fyld Dyld Dm CMD GCA 6 22.53** 2.02 0.21 6.77* 0.87** SCA 21 9.48** 4.31** 0.32** 4.30** 0.50** Error 108 2.52 0.22 0.023 0.973 0.099 GCA:SCA   2.38 0.47 0.66 1.57 1.74 Rootno=average root number per plant, Fyld=fresh root yield, Dyld=Dry yield, Dm=Dry matter content, GCA=general combining ability, SCA=specific combining ability, DF –degree of freedom * P ≤ 0.05, ** P ≤ 0.01

Table 3. Mean squares for GCA and SCA for CMD, yield and yield components of cassava genotypes for forest ecological zone (2009/2010) Source Df Rootno Fryld Dyld Dm CMD GCA 6 30.29** 3.08* 0.25* 2.85* 0.64** SCA 21 11.97** 7.47** 0.65** 4.36** 0.54** Error 108 2.72 0.27 0.02 0.89 0.11 GCA:SCA   2.53 0.41 0.38 0.65 1.19 Rootno=average root number per plant, Fyld=fresh root yield, Dyld=Dry yield, Dm=Dry matter content, GCA=general combining ability, SCA=specific combining ability, DF –degree of freedom * P ≤ 0.05, ** P ≤ 0.01

Results and discussion The ratio between GCA and SCA mean squares for yield, CMD and number of roots was greater than 1.0 indicating the predominance of additive gene action The predictability ratio was 0.83 and 0.74 for root number and CMD respectively, indicating the importance of GCA and additive gene action GCA:SCA ratio indicated that the SCA was larger than GCA for fresh root yield indicating environmental effects on the trait and confirms the non-additive effects mainly determining expression of root yield

Conclusions Progenies from crosses Dabodabo x Kwasea, Debor x Lagos and Lagos x Kwasea were the best combinations for CMD resistance Dabodabo for DM 0.51 Kwasea and Tuaka for CMD Narrow-sense heritability was 0.61 for root number and 0.52 for CMD

Acknowledgement Cornell University, New York, USA University of the Free State, South Africa IPICS, Uppsala University, Sweden GCP (Generation Challenge Programme),Mexico CIAT (Centro International de Agricultura Tropical) Colombia IITA (International Institute of Tropical Agriculture), Ibadan, Nigeria Government of Ghana and CSIR- CRI WAAPP LEGON,UCC CSIR Institutes CSIR-CRI PARTNERS

Thank You! Welcome for collaboration