Fine Mapping And Functional Verification Of The Node Of First Fruiting Branch Gene On Chromosome D08 In Upland Cotton

Cultivation of early maturing varieties of upland cotton is beneficial to improve the multiple cropping index of land,so as to alleviate the conflict between cotton and grain for land.The position of the first branch of cotton is the most direct index character to determine whether cotton is precocity,which is closely related to the opening period of cotton and affects the yield of cotton.In this study,F₂ and F_2:3 populations constructed from light-sensitive semi-wild upland cotton Y104 and modern cultivated cotton NLD402were used as mapping materials,and candidate genes were mapped on chromosome DT08of upland cotton by genetic mapping.Through resequencing,differential expression analysis and virus-mediated gene silencing tests,the molecular mechanism of bud emergence regulated by candidate genes was preliminarily revealed.The specific results are as follows:1.A total of 514（Y104×NLD402）F₂ isolates were scanned with 17 pairs of polymorphism primers and their genetic maps were constructed.Combined with the results of BSA mapping,a major QTL for the node position of the first fruit was located between the terminal markers D08-2975 and D08-3016 on the D08 chromosome.The LOD value was16,and the phenotypic contribution rate was 14.02%.The genetic distance between the two markers was 2.52 cM.2.To take advantage of selected 7 polymorphism markers,to（Y104 x NLD402）F_2:3 group a total of 789 individual tag scanning and genetic map construction.A QTL with a LOD of26.7 and a phenotypic contribution rate of 15.2%was repeatedly mapped from HAU-23 to HAU-32 at a physical location of 68217758 bp to 68301541 bp（about 0.2 Mb）in the above QTL segments.3.There were 24 genes in the location interval,and 3 candidate genes were screened based on the reseqencing results.The candidate gene GH＿TIFY 10A was found to have many base mutations in the coding region between Y104 and NLD402 after cloning comparison.The sequence of Y104 was consistent with the sequence of TM-1,while NLD402 had 54bp fragments inserted at the N end of the coding region.4.In the upland cotton public database（Cotton FGD,NAU）,Gh＿TIFY 10A has a higher expression level when the stamens,receptacles,calyx and other organs of the reproductive organs start to develop.RT-qPCR showed that the expression of Gh＿TIFY 10A was significantly up-regulated before and after NLD402 budding.The subcellular localization results of Arabidopsis and tobacco showed that Gh＿TIFY 10A gene was expressed in the nucleus and participated in genetic regulation.5.The VIGS test in NLD402 showed that after the intervention of GH＿TIFY 10A,the average node position of fruit branch in the experimental group was higher than one node in the negative control group,and the average flowering time was about 14 days later,indicating that the expression of GH＿TIFY 10A gene affected the appearance of node position of the first fruit branch,and also had an effect on the flowering time.