Genotype X Environment Interaction for Storage Root Yield in Sweetpotato Under Managed Drought Stress Conditions

Most crops, including sweetpotato vary widely in yield performance across different agro-ecological environments. This study was set up to determine the genotype x environment interaction (GEI) for storage root yield performance of 24 sweetpotato genotypes in eight environments; two locations - Kiboko and Thika, two moisture stress conditions - drought stress and no drought stress, and two years - 2011 and 2012 in Kenya. Plots of three rows each of 10 plants per genotype, at density of 0.9 m × 0.30 m were panted during dry season under split plot design replicated twice. Managed irrigation was applied to control moisture stress during the growth period. Fresh storage root yield (FSR) data was collected, and drought susceptibility indices (DSI) determined. Additive Main Effects and Multiplicative Interactions (AMMI) genotype main effect by genotype-environment (GGE) interaction biplots and regression analyses were done using Genstat 14th edition to determine GEI effects. The environment, genotype main effects, and the GEI were all significant (P < 0.001). The DSI showed significant variation of genotypes in different environments. The highest yielding genotypes across the environments were G7, G14, G15, and G10 while most stable genotypes were G5, G22 and G2 and the least stable was G24. Thus, genotypes G5, G22 and G2 may be used across environments, while genotypes G7 and G14 could be used, 1) in specific locations to boost production under unpredictable rainfall conditions, 2) incorporated into drought screening breeding programmes to develop a new generation of drought tolerant sweetpotato varieties to meet changing climatic conditions.