Abstract
Cassava root yield under diverse environments is influenced by morpho-physiological traits that are in turn influenced by genotype, environment, and genotype × environment interaction (GEI). Most GEI analyses in cassava have been limited to root yield with less emphasis on stability of other yield-related traits. This study was carried out to assess the effect of GEI on some morpho-physiological traits in cassava and key traits that are useful for selection in different environments. The study utilized 20 cassava genotypes evaluated in six environments, namely, Fumesua 2013 and 2014, Nyankpala 2013 and 2014 (irrigation), and Nyankpala 2013 and 2014 (no irrigation). The genotypes were arranged in a randomized complete block design (RCBD) with three replications and assessed for a number of morpho-physiological traits, root yield and yield components. The data were subjected to analysis of variance using SAS statistical package. Subsequently, the GGE biplot was used to carry out genotype × environment, genotype × trait, and environment × trait interaction analyses to determine the specificity of genotypic performance and traits linked to particular environments. The results indicated significant (P<0.05) GEI effect on all traits except leaf temperature. The genotype × trait biplot analysis revealed closely related traits and those associated with root yield and genotypes that show weakness in these traits. Both environment × trait biplot and principal component analyses identified traits with higher discriminatory power among genotypes in various environments particularly in the dry environments. These can be used as secondary traits to select drought-tolerant genotypes. From this study, the GGE biplot was useful in identifying traits associated with specific genotypes in different environments to aid in selection. Moderate broad-sense heritability estimates werefound for storage root yield, harvest index, plant height, ratio of storage rootlength to girth, and cassava mosaic disease score indicating that progresscan be made through selection for these traits.
Highlights
Cassava (Manihot esculenta Crantz) serves as a staple food for millions of people in sub-Saharan Africa because it provides a cheap source of carbohydrate per unit area
In addition to the monthly rainfall, a monthly average of 162.53 mm of irrigation water was supplied to the irrigated plots in 2013, whereas a monthly amount of 170.66 mm was applied in 2014. e mean monthly rainfall for Fumesua in 2014 (135.00 mm month−1) was higher than what was recorded in 2013 (95.59 mm month−1) as well as the other environments (NIR13 = 82.64; no irrigation-2014 (NIR14) = 98.42)
Apart from leaf temperature, all the other traits were significantly influenced by genotype × environment interaction (GEI) effect. ough significant genotypic variation was observed for stomatal conductance, it was strongly influenced by the environment as well as GEI which resulted in its low broad-sense heritability
Summary
Cassava (Manihot esculenta Crantz) serves as a staple food for millions of people in sub-Saharan Africa because it provides a cheap source of carbohydrate per unit area. It is widely cultivated in most farming systems in Africa due to its ability to give appreciable yields in marginal ecologies where other crops will fail [1]. The mechanisms underlying these traits are regulated by several genes within the cassava genome which can be targeted in breeding to select improved cassava genotypes for drought-prone ecologies [10,11,12]. The phenotypic expression of these genes is influenced by the environment and genotype x environment interaction (GEI) leading to crossover performances in different environments [13, 14]
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