Abstract
Twenty cassava genotypes were arranged in a randomised complete block design with three replications and assessed for growth and yield stability using the additive main effect and multiplicative interaction (AMMI) analysis. Highly significant (P<0.001) effects of genotype, environment, and genotype ⁎ environment interaction were observed for all traits studied. The AMMI analysis of variance indicated that genotype accounted for 51% of the total sum of squares for height at first branching followed by environment (33%) and interaction (15%). For fresh root yield, environment effects accounted for 37% of the total sum of squares, whilst genotype and interaction accounted for 32% and 29%, respectively. Genotypic variances for harvest index (HI), plant height, storage root yield, and dry matter content contributed a greater proportion of the phenotypic variance indicating stronger genetic control. This suggests better chance of progress in the genetic improvement of these traits. Genotype MM96/1751 combined high yield with stability according to the yield stability index ranking across environments. On the other hand genotypes UCC 2001/449 and 96/1708 though high yielding were unstable according to AMMI stability value scores. However they can be tested further in more environments to ascertain their specific adaptability for release to farmers for cultivation to boost cassava production and ensure food security.
Highlights
Cassava (Manihot esculenta Crantz) is grown in a wide range of environments but severe yield losses occur in traditional cultivars grown by poor farmers [1,2,3]
This is because genotypes exhibit different levels of phenotypic expression under different environmental conditions resulting in crossover performances [5]
Crossover performances by genotypes in different environments result from differential responses under varying environmental conditions [6, 7]
Summary
Cassava (Manihot esculenta Crantz) is grown in a wide range of environments but severe yield losses occur in traditional cultivars grown by poor farmers [1,2,3]. Root yield losses in poor drought-prone environments can be as high as 80% when compared with root yield in optimum environments [4]. This is because genotypes exhibit different levels of phenotypic expression under different environmental conditions resulting in crossover performances [5]. Crossover performances by genotypes in different environments result from differential responses under varying environmental conditions [6, 7]. This was defined as genotype∗environment (G ∗ E) interaction [8]. Studies on cassava’s performance in different environments have indicated significant G ∗ E effect for root yield and yield components [9,10,11,12]
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