Fine Mapping And Identification Of Early Maturity Related Genes In Cotton(Gossypium Hirsutum L.)

Crop early maturity is a complex quantitative trait,and the early flowering is the key trait of cotton early maturity.In this study,two upland cotton cultivars,“Lumianyan 37”?late flowering?and“Lumianyan 19”?early flowering?were used as parental lines to develop F₂ and F_2:3 segregating populations for evaluation thephenotype of flowering and budding.We selected 20 extreme early flowering plants to construct early flowering pool and 20 extreme late flowering plants to construct late flowering pool in the F₂ segregating population.Next generation sequence technology?NGS?was used to sequence the parents and the two pools and identify the informative SNPs and InDels.By using the InDel,SNP and SSR markers,we construct a molecular genetic map for fine mapping the early flowering and early budding QTLs.The main results were listed below:1.The flowering time of LMY19 was stable,which was about 9-10 days earlier than LMY37 under normal spring sowing time.The budding and flowering times of F_2:3 populations showed normal distribution,suggesting that the early budding and flowering in cotton was a quantitative trait.2.The BSA-seq method was used to re-sequence the samples of LMY19,LMY37 and the pools of early and later flowering.The test indexes of each sample were Q20?92.25%,Q30?85.22%,and the GC content was normal.Then the short reads from the separate groups were aligned to the LYM37 reference genome and preformed SNP-calling and InDel-calling,??SNP-index?and??InDel-index?were calculated by QTL-seq method.There was an SNP imbalance in the physical position of 12 Mb-27.17 Mb and 38.94 Mb-42.23 Mb at Chr.17?D3?,and the InDel-indexs were 13.4 Mb to 26.2 Mb and 38.66 Mb to 43.21 Mb at the same chromosome.The??SNP-Index?and??InDel-index?of the above mentioned chromosomal region were greater than the thresholdunder the 95%confidence level.And this region was determined as a candidate interval for early maturity QTLs of upland cotton.3.The budding and flowering time were detected in the populations of F_2:3 lines by the softwares of WinQTLCart2.5 and IciMapping V4.0.Two QTLs of flowering time?qFT-17-1,qFT-17-2?and two budding time?qBP-17-1,qBP-17-2?were detected.The candidate intervals of the QTLs were shortened to 15.96 Mb-25.68 Mb and 40.33 Mb-41.40 Mb in Chr.17?D3?of the upland cotton.4.According to the annotation of ANNOVAR,Fifty-one and twenty-four candidate genes were identified in the candidate regions.Furter,identified three possible candidate genes related to flowering.The structure analysis and expression verification were carried out by using bioinformatics and qRT-PCR.