Identification Of QTL For Yield And Fiber Quality Traits In Upland Cotton (Gossypium Hirsutum.L) RIL Population

In this research, a RIL population with 196 lines was developed from the upland cotton cross of SGK9708 and 0-153. The female parent SGK9708 was derived from Zhongmiansuo41 which is widely popularized variety and the male parent 0-153 is an excellent variety of upland cotton with high fiber strength gene from Asiatic cotton. Multi-environmental experiments in six environments were conducted at five locations in two years, identification of QTLs and analysis of epistasis and QE interaction for yield and fiber quality traits were also conducted for detecting major QTLs which expressed stably in multiple environments and explaining the genetic mechanism of yield and fiber quality traits, which would provide an important reference for marker-assisted breeding.Phenotype data of yield and fiber quality traits in 6 environments showed normal distribution, which fit to the quantitative trait conditioned by multiple micro-effect genes. The correlation analysis showed that lint percentage was significantly negative correlation with main fiber quality traits, seed index was significantly positive correlation with main fiber quality traits, most of seed cotton yield and lint yield traits were not significantly correlation with main fiber quality traits.A total of 8256 of SSR primer pairs from different sources were used to screen polymorphism between two parents and 225 polymorphism loci were amplified from 191 primer pairs in 196 RIL lines.186 markers were mapped into 34 linkage groups by linkage analysis of Joinmap3.0. The linkage map spanned 827.84cM, had an average interval of 4.45cM between two markers and approximately covered 18.6% of the cotton genome.A total of 93 QTLs for yield traits and 94 QTLs for fiber quality traits were detected in single environment by Composite Interval Mapping method. QTLs of five traits (lint percentage, seed index, fiber length, microniare and fiber strength) expressed stably in multiple environments.16 QTLs could be detected at least in 5 environments, which including 4 QTLs for lint percentage,2 QTLs for seed index,4 QTLs for fiber length,1 QTL for fiber uniformity, 2 QTLs for micronaire and 3 QTLs for fiber strength. Major QTLs for lint percentage were mainly located on chromosome 13 and chromosome 16; major QTLs for seed index were mainly located on chromosome 7; major QTLs for main fiber quality traits were mainly located on chromosome 25 and chromosome 7.Analysis of epistasis and QE interaction for yield and fiber quality traits were conducted by Mixed Linear Model CIM. A total of 27 pair epistatic interactions and 6 QE interactions were detected. For epistasis, most were interaction between background loci (18 pairs); for QE interaction, most were combined action of additive effect and QE interaction (5).The influence of epistasis and QE interaction could not be ignored when studying major QTLs because the complex genetic mechanism caused by the excision of epistasis and QE interaction.