Abstract

There are concerted efforts in promoting cassava production in sub Saharan Africa as a staple food crop as well as income earner at both household and commercial level. These efforts can bear meaningful results if breeding strategies are properly coordinated. Efficient breeding methods require a thorough understanding of the genetic background of planting materials. Therefore, a genetic study was conducted to establish the genetic basis of cassava genotypes for root weight, root number/plant, root length (cm), above ground weight, harvest index, cassava mealy bug and cassava green mite by mating six cassava genotypes using a diallel method. The generated F1s were evaluated using a randomized complete block design (RCBD) replicated thrice. The analysis of variance revealed highly significant (P< 0.001) genetic variation among the genotypes for all the traits except for cassava mealy bug, indicating the presence of high variability among genotypes. Thus, selection among these genotypes could lead to good progress for the improvement of the target traits. Mean squares for both general combining ability (GCA) and specific combining ability (SCA) were highly significant for all traits except for harvest index and cassava green mite for GCA and SCA respectively which suggested involvement of additive and non-additive component of heritable variance in the inheritance of all these traits. However, the proportions of additive variance to the total genetic variances (that is, 2δ²gca/(2δ²gca + δ²sca) showed that crossing for these traits and making selection from such crosses, about 41 to 100% of the improvement would be expected to come from SCA and less than 59% from GCA which indicated a greater role played by non-additive genes. Overall, results indicated that it would be readily possible to breed for high yield from this set of genotypes.

Key words: Breeding, combining ability, gene action.