G×E Interaction Effects on Yield and Yield Components of Landraces and Improved Cassava Genotypes in the Savanna Regions of Nigeria

摘要

Genetic enhancement of cassava aimed at increasing production and productivity through theprovision of broad-based improved germplasm is a major goal for Cassava breeders. At IITA, Nigeria, eighteenvarieties comprising twelve landraces and six broad-based and improved varieties were evaluated at fourlocations in 3 years in a randomized complete block design in four replicates to determine variability amongcultivars for yield components and adaptation to different environments. Results showed fresh root yield wassignificantly correlated (P<0.001) with number of roots, harvest index, shoot weight and number of standsharvested. AMMI analysis partitioned main effects into genotypes, environments and G×E with all thecomponents showing highly significant effects (P<0.001). Environment had the greatest effect (70.3%),G×E interaction (19.0%) and genotype(10.7%). AMMI1 and unadjusted means selected the same winner in nineout of twelve environments (75%), but differently in three environments. The GGE biplot (E and G×E interaction)delineated environments into three mega-environments. Cultivar 4(2)1425 (moderately yielding) was the moststable and specifically adapted to Zaria. ABBEY-IFE, ATU-IWO and 2ND-AGRIC though moderately yieldingwere highly tolerant to CMD, suggesting a rich resource within the germplasm that could be enhanced forfurther genetic improvement of the crop.