Genetic distance and specific combining ability in cassava

Cassava ( Manihot esculenta Crantz) is an important source of energy in the tropics. Its starchy roots are valuable for food security as well as for different industries. Cassava is an outcrossing crop and its breeding is based on the use of heterozygous progenitors. Non-additive genetic effects are important for fresh root yield (FRY) and can be exploited through reciprocal recurrent selection. Results from three diallel studies (with 9-10 progenitors), conducted at three different environments (sub-humid, acid soils and mid-altitude valleys) in Colombia, have already been published for FRY. In this article, phenotypic analysis of dry matter yield (DMY) was also conducted. Specific combining ability effects and actual FRY and DMY data was linked to Nei’s genetic distances which were estimated through a set of 95 SNPs diagnostic of the cassava diversity. Results from regression analyses indicated inconsistent and generally weak associations between genetic distances and performance of the F1 families per se (r 2 values ranging from 0.01 to 0.10) and specific combining ability effects (r 2 values ranging from 0.00 to 0.28) for the two variables analyzed.