QTL Mapping For Important Agronomic Traits In Gossypium Hirsutum L. Cir-6 Population

Cotton (Gossypium) is the world's most important natural textile fiber and a significant oil crop.In recent years, improvement in the quality of cotton fiber has been extremely important because of changes in spinning technology. Negative correlation between yield and quality make it difficult to improve, simultaneously. So it is important to select high priorities of yield and quality properties from markers, which have close linkage with QTLs. So two elite Gossyium hirsutum L. line, which were Acala1517 and Dezhou047, were used as parents to construct a RIL (Recombined Inbred Line) population of cotton (CRI-6). CRI-6 was used to construct linkage group using 11358 pairs of SSR primers. Quantitative trait loci (QTL) analyses were performed by means of Mixed Linear Modle Composite Interval Mapping. QTL analysis may provide a useful tool for breeders.The majority of agronomic traits for CRI-6 showed normal distribution in the different years. Correlation coefficients between phenotypic traits were caculated in each of CRI-6 lines. Growth and development stages (GDS) and percentage of pre-frost seed cotton (PPSC) were negative correlation with another growth trait, respectively. GDS and PPSC, first fruiting branch node (FFBN) and buding steage (BS) were positive correlation. Seed yield (SY) and lint yield(LY) also showed positive correlation. SY and LY were positive correlation with boll size (BZ) and bolls number (BN), respectively. SY showed positive correlation with LY. Lint percentage (LP) and BN were negative correlation with GDS and PPSC, respectively. Uniformity index (UI) showed significant correlation with growth traits (except boll-forming stage, BFS). LP were positive correlation with fiber traits (except micronaire (MV) and UI), and seed index (SI) was reverse.Two hundred and nine of a total of 11358 SSR primer pairs (1.84%) revealed polymorphisms between the parents. Of these, 90 SSR primer pairs were assigned to 22 linkage groups with a total map distance of 663.08 cM, which covered 13.1% of the total recombinational length of the cotton genome.QTLs were analyzed by Mixed Linear Model Composite Interval Mapping, using Windows QTLNetwork 2.0. A total of 52 major QTLs and 53 pairs of additive epistatic QTLs for important agronomic traits were detected in the three different years. The stable major QTLs of FFBN, PPSC, seed yield (SY), lint yield (LY), lint persentsge (LP), seed index (SI) were mapped in different years, respectively. And phenotypic variance major QTL of SI was over 22%. Two pairs of stable additive epistatic QTLs of LP were detected in different years, and one pair of stable additive epistatic QTL of FS was detected in different years.