Mapping And Identifying Candidates Of Drought-tolerant Genes In The Tomato Introgression Line IL9-1

Drought is one of the top three natural disasters,which happens frequently around the world and affects crop productivity and quality seriously.Tomato(Solanum lycopersicum)is an important fruit-bearing vegetable,with a wide growth area and high total yield.Tomato is also an important model species for scientific research,however,cultivated tomato is sensitive to abiotic stress such as drought.Traditional breeding can improve the drought resistance of tomato,but the selection process is complicated and the cost is high,thus the breeding efficiency is very low.As the gene responsive network and mechanism underlying drought tolerance remains to be elucidated,it largely limits the process of genetic improvement of the drought tolerance of tomato.As a result,it has become a hotspot and an important development strategy to explore drought tolerant genes in tomato as well as other crops.This work aims at mapping and identifying drought-tolerant gene candidates in IL9-1,an important drought-tolerant introgression line characterized previously in our research group.The main results are as follows:1 Primers were designed based on the putative InDel sequences between IL9-1 and the recurrent parent M82,a total of 19 polymorphic InDel markers were developed after PCR confirmation.2 A sub-IL population with 50 lines were constructed by crossing IL9-1 and M82,followed by selfing and InDel marker analysis.3 By combining of the genotype data and drought screening results of the sub lines,it was found there was one or more QTLs within the introgressed region of IL9-1.The drought-tolerant gene was narrowed down to two 708 kb and 131 kb,and genes encoding ascorbate peroxidase,calcium/calmodulin binding protein,aquaporin,pathogenesis related protein,transcription factors such as MYB and bZIP,and ubiquitin ligase were found to located in the mapped regions.4 A RNA-seq analysis was carried out in M82 and IL9-1 with drought treatment.After the stress application,1725 and 746 genes were identified to be differentially expressed in M82 and IL9-1,respectively.Among them,69 genes were specific to IL9-1.Hormones pathways of ABA,salicylic acid and brassinosteroid were enriched in GO annotation and pathway analysis.According to the mapping results and the RNA-seq analysis,13 specific genes including a gene(Solyc09g007020.1.1)encodes pathogenesis-related protein and a gene(Solyc09g007150.2.1)involved in glutathione pathway were obtained.