Genotype-By-Environment Interaction Effect on Storage Root Yield and Yield Components of Cassava (Manihotesculenta crantz) Genotypes in Different Agroecologies of Southwest Ethiopia

Abstract

The storage root yield of cassava is highly affected by genotype by environment (GEI) interactions. The objectives of this study were to assess the  nature and magnitude of GxE interactions of cassava genotypes based on environment evaluation trials and to identify mega-environments for  future breeding strategies. The study was conducted across six environments in southwest Ethiopia. Ten cassava genotypes and one local check  were evaluated by using a randomized complete block design with three replications. Data from totalstorage root yield, root dry weight and root  diameter were collected and analyzed using the additive main effect and multiplicative interaction and genotype main effect plus genotype by  environment interaction bi-plot analyses. The combined analysis of variance showed significant variation for genotypes, locations, and crop year  and their interactions for root dry weight and root diameter. Genotypes 8 (AAGT 191) and 6 (AAGT 108) had broad adaptability for total storage root  yield, whereas, genotypes 7 (AAGT 189), 11 (local), 10 (AAGT 200) and 4 (45/72NW) were superior for root dry weight. For high total storage root yield  and root dry weight, environments 2 and 4 were epitome and highly close to the ideal environment. Overall, environment 4 was the most  suitable environment for discriminating among genotypes and for being a representative test environment. Three mega-environments (MGE) were  identified from this study for cassava breeding; where environments 2, 5 and 6 combined into MGE-1, environments 3 and 4 fell into a separate  MGE-2 and MGE- 3, respectively.