Fine Mapping And Candidate Gene Cloning Of QFL-12-5 In Chromosome Introgression Line From Gossypium Barbadense ×Gossypium Hirsutum

Cotton is an important economics crop,which has important economic value.cotton fiber is the important source of natural fiber,and the important raw material of modern textile industry.With the the gradual improvement of human’s daily life and the development of cotton textile industry technology,the requirements for fiber quality have also been improved.These make the principal purposes of cotton breeding also shift from solely increasing yield to simultaneously improvement of both yield as well as fiber quality.Fiber length is one of the important indexes of the cotton fiber quality,so increasing the fiber length of cotton has become an important goal of cotton breeding programs.The previous studies showed that the qFL-12-5 could be detected in multiple environments and populations and it located between SSR markers of HAU0734 and NAU4889 with the explained phenotypic variations of 11.25%and the additive effect of 0.55 mm.For fine mapping,the single chromosome fragment introgression line with target interval were selected from the CSSL population,and was hybridized with the recurrent parent and self-crossed to construct the primary population to evaluate the stability of the QTL using SSR markers.And the single-fragment homozygous line with the target region in the primary population was screened using marker-assisted selection to construct a subgroup large near-isogenic introgression lines(sub-NIILs).For fine mapping,a comprehensive analysis of the QTL region was conducted and SSR markers were developed within this region based on the genomic sequencing database of G.hirsutum.The high-density genetic map of the target interval was constructed,and the fine mapping of qFL-12-5 was completed by combining the fiber quality data.The initial mapping result showed that qFL-12-5 could be detected in 2016 BC6F2 and 2017 BC6F2:3(two environment)primary population,the explained phenotypic variations and the additive effect were 15.45%and 0.67 mm for 2016 BC6F2,13.42%and 0.52 mm for 2017 BC6F2:3(anyang,henan),16.76%and 0.678mm for 2017 BC6F2:3(kuerle,xinjiang),respectively.The fine mapping result diaplayed that qFL-12-5 was mapped in a short genetic distance of 0.8 cM,and in a physical distance of 18.4 kb between SSR markers of M-155 and SWU17439.According to the databases of upland cotton sequencing and gene annotation,this region harbored a total of six related genes.Combining the results of qRT-PCR,and the transcriptome sequencing of fiber in the different period,and the sequence analysis of cloning these genes in original parent,GH_A12G2192,was identified as the candidate genes related to fiber development.This research lays an important foundation for further gene function identification and molecular elucidation of fiber development mechanism.