Genetic Analysis of Major QTLs and Epistasis Interaction for Yield and Fiber Quality in Upland Cotton

【Objective】 The aim of this investigation was to better understand the genetic base of yield and fiber quality traits in upland cotton. Major quantitative trait loci (QTL) associated with yield and fiber quality and epistasis interaction in controlling these traits were mapped using a genetic linkage map which comprised 471 loci, spanned 3 070.2 cM and covered 65.88% of the whole cotton genome. 【Method】 An F2:3 population from DH962 × Jimian5 was used to evaluate yield and fiber quality. Major QTLs were identified by composite interval mapping method on WinQTLCartV2.5. Two-way digenic interactions analysis was conducted using EPISTACY. 【Result】 Nine major QTLs were detected for six yield traits and five for fiber quality traits. No QTLs were detected for fiber uniformity ratio and fiber strength under the significant threshold LOD scores. A total of 75 significant digenic interactions were detected, most of them were non-QTL × non-QTL interaction; most of the interaction types were additive × dominance interaction and dominance × additive interaction. Many digenic interactions were detected for lint percentage and fiber length, and only few for boll number and lint index. One common major QTL for SCW, LW and SI was detected on LG1. Common digenic interactions were also found for some correlated traits: one for SCW, LW and MV; four for LP and FL. 【Conclusion】 Except for major QTLs, epistasis played an important role in the genetic basis of yield and fiber traits in upland cotton. The low effect of major QTLs and the digenic interactions will make it more difficult and more complex for maker-assisted selection in cotton breeding. Correlated traits were controlled by same QTLs/digenic interactions, which will be helpful to select these traits simultaneously.