Genotype × environment influence on cassava performance

Abstract

To study the relative influence of genotype, environment and genotype × environment (g × e) effects on six agronomic traits of importance, fifteen morphologically diverse cassava genotypes were tested in 12 environments, comprising six locations over two seasons per location. The locations were representative of three major agro-ecological zones in Peninsular Malaysia, as well as of two major soil types: mineral and peat. Fresh root yield, commercial root number and root cyanide content were not associated with soil type, but high yield on peat might be related to high rainfall. Peat environments seemed to favour high harvest index except when there was a prolonged drier season. On mineral soils, high soil P and K contents may explain high harvest indices. Low rainfall prior to harvest may increase root cyanide content. Root starch content may be associated with high pH on mineral soils. Dry matter content in the roots was greatest when soil pH exceeded 4.6, except when rainfall was heavy just prior to harvest. Genotype effects were strongest in controlling root cyanide content, harvest index and root dry matter content, while environment was the main source of variation for commercial root number and fresh root yield. Location × season effects were the most prominent of the environment components. Season had a significant effect only in the expression of root dry matter content, but was nevertheless smaller in magnitude than the genotype effect. Genotype × environment (g × e) effects were significant for fresh root yield, commercial root number, harvest index, and for root starch and cyanide contents. Except for fresh root yield and commercial root number, these effects were smaller than the genotype effect. Only root cyanide content showed a linear g × e relationship with environment.