Abstract:

Yield and yield component traits of cotton are inherited quantitatively with low heretibility and tend to vary with environmental variation. Classical quantitative genetics has indicated that epistasis is the foundation of such complex traits. In this study, a genetic linkage map was constructed using the recombinant inbred line (RIL) populations developed from an elite upland cotton hybrid Xiangzamian 2 (XZM2). Yield and yield component traits were investigated in F8 and F9 generations of RILs in three environments in China. The purpose of the study was to map epistatic QTL and analyze QTL by environment interactions in yield and yield components of cotton. Epistatic QTL were detected for all yield and yield component traits. Altogether 16 pairs of QTL interactions (AA) were identified. However, only 4 of the loci involved had single-locus effects, indicating the complexity of epistasis and their important contributions to yield and yield component traits. Altogether 17 pairs of QTL by environments interactions (AE) and 14 pairs of epistasis by environment (AAE) interactions were detected, indicating that environment influenced yield and yield componment traits greatly. The results suggest that epistatic effects might be importantly involved in the genetic basis of heterosis in the cotton hybrid of XZM2. Superior genotypes under different environments were predicted for all traits, indicating that there existed potential of increasing yield and yield components from XZM2-derived RILs. Due to influence of AE and AAE, the predicted SLs in different environments might be different. In cotton breeding, it is a practical strategy to perform breeding program according to special environment.

Key words: Gossypium hirsutum L., Epistasis, QTL, Superior lines