Genotype x environment interactions for shoot fly resistance in sorghum (Sorghum bicolor (L.) Moench): Response of recombinant inbred lines

Sorghum shoot fly (Atherigona soccata) is a serious pest that destabilizes the performance of sorghum cultivars and ultimately reduces sorghum production in many parts of the world. Identifying sorghum genotypes with stable resistance to shoot fly is important as it helps to reduce the cost of cultivation and stabilizes yields. In the present study, our objective was to identify stable shoot fly resistant genotypes among 385 recombinant inbred lines (RILs) of a cross between a susceptible parent and a resistant parent. We evaluated this set of RILs in eight environments over three years (2006-2008) for shoot fly resistance and component traits. Non-significant genotype environment (G x E) linear component and significant pooled deviation for deadheart percentage indicated that the performance of genotypes was unpredictable over the environments. However, five lines had deadheart percentages much less than the population mean with regression coefficient (bi) values close to unity, and non-significant deviation from regression, indicating that they have stable shoot fly resistance and are well adapted to all the environments. Additive main effect and multiplicative interaction (AMMO analysis partitioned main effects into genotype, environment and G x E interacts with all the components showing highly significant effects (p < 0.001). Environment had the greatest effect (69.2%) followed by G x E interactions (24.6%) and genotype (6.2%). Low heritability and high environmental influence for deadheart percentage suggested that shoot fly resistance is a highly complex character, emphasizing the need for marker assisted selection. We observed transgressive variation in the RIL population for all the traits indicating the contribution of alleles for resistance from both resistant and susceptible parents. Since the alleles for shoot fly resistance are contributed by both resistant and susceptible parents, efforts should be made to capture favourable alleles from resistant and susceptible genotypes. (C) 2011 Elsevier Ltd. All rights reserved.