QTL Mapping Of Plant Height And Branch Number And Functional Verification Of Candidate Genes Related To Chromosome 25 In Upland Cotton

Upland cotton(Gossypium hirsutum L.)is one of the natural fiber crops,which provides raw materials for the textile industry.Plant height,fruit branch number and fiber strength are one of cotton yield and quality traits,which are important target traits in cotton genetic improvement.Plant height,number of fruit branches,and fiber strength are all quantitative traits,which are controlled by multiple genes and are greatly affected by the environment.In recent years,a large number of QTLs related to cotton agronomic and quality traits have been reported.Among them,there are few QTL related to plant height and fruit branch number,andfew studies have been conducted on functional verification of the genes within the QTL confidence interval related to fiber quality.In this study,we used the Cotton SNP80 K chip genotyping data in CCRI 70 Recombinant inbred population,to reconstruct the high-density genetic map with the latest version of the upland cotton sequencing data as the reference genome,and identify QTL of the plant height and the number of fruit branches.A total of 69 QTLs were mapped for plant height traits,9 of them identified in multiple environments;and a total of 63 QTLs for the fruit branch number traits,including 11 of them identified in multiple environments.In the analysis of consistency,a QTL on chromosome 25 for plant height was consistent with the previous reports.There are495 and 446 genes in the QTL confidence interval of plant height and fruit branch number,respectively.Combining annotation information,expression pattern and annotation of Arabidopsis homologous genes,6 genes(GH＿D03G0586,GH＿A01G1023,GH＿A01G1055,GH＿D03G1142,GH＿A13G0765 and GH＿D07G0421)were finally identified as the potential candidate genes.The functional verification of the candidate genes Gh＿D06G0805,Gh＿D06G0806,Gh＿D06G0807,and Gh＿D06G0809 in the stable QTL q FS-chr25-4on chromosome 25 for fiber strength was carried out.In the experiment,the expression level was compared,and the transcriptome data was verified by q RT-PCR,it showed that Gh＿D06G0807 and Gh＿D06G0809 had a dominant expression in the fiber.The results of subcellular localization experiments showed the expression positions of the four candidate genes in the cell.The Arabidopsis overexpression vectors for the 4 candidate genes were constructed,and gene transformation of Arabidopsis thaliana by Agrobacterium injection and identification of the phenotype of overexpressing Arabidopsis plants.The results showed that compared with wildtype Arabidopsis(WT),the growth of the Gh＿D06G0809 transgenic line was significantly faster and its roots increased significantly;the leaf of Gh＿D06G0806transgenic plant was relatively wider and the stem was slightly shorter than that of WT;Gh＿D06G0805 transgenic plants died after transplantation;Gh＿D06G0807 did not show the significant phenotype difference from WT.This study uses forward genetics to locate QTL of the target traits,verify the accuracy of its positioning in multiple environments,and identify genes within the QTL confidence interval.Through expression and metabolic pathway analysis,the candidate genes were preliminary determined,and the overexpression of the candidate genes in Arabidopsis showed the function for the potential improvement of cotton target traits,this laid the imortant foudation for cotton improvement.