Screening And Identification Of Heat-resistant Tomato Strains And Mapping Of Heat-resistant Genes

Tomato（Solanum lycopersicum L.）is an important vegetable for greenhouse cultivation and has relatively strict temperature requirements during growth and development.The selection of heat-tolerant tomato strains is therefore of great importance for the development of new heat-tolerant varieties,as tomato is prone to high temperatures in greenhouse over-summer cultivation,resulting in plant growth,reduced fruit set,fruit yield and quality.In order to clarify the mechanisms of heat tolerance regulation and key genes for heat tolerance in tomato,this study was conducted to identify and screen tomato heat tolerant lines and obtain heat tolerance candidate genes by BSA-seq sequencing through high temperature stress:1.Eight tomato lines obtained by self-crossing for many years were used as test materials to study the fruit set rate,physiology and fruit quality traits of each tomato line under high temperature conditions,and it was found that tomato lines CH and ZHY were better and lines DH and 46 were less heat resistant.MDA significant positive correlation was found with chlorophyll content.2.Four tomato lines CH,ZHY,DH,46 were subjected to high temperature stress at seedling stage,and the main characters of the four tomato lines were studied.The results showed that the heat resistance of tomato strain CH was strong,and that of tomato strain DH was poor;Through the correlation analysis of the main characters of each tomato strain at seedling stage after high temperature stress,it was found that plant height was significantly positively correlated with stem diameter and plant width,and electrical conductivity was significantly positively correlated with MDA content.3.The heat-resistant strain CH,the non-heat-resistant strain DH and their constructed F₂populations were subjected to BSA-seq sequencing analysis,and a candidate region of 6.32 Mb in size,including 752 candidate genes,was obtained on chromosome 3.Five（DG3K,HYDR,PARS2,RPE and ALDH）were screened among the metabolic pathways in the candidate region that are associated with heat tolerance in tomato.The relative expression of the candidate genes was analyzed,and it was tentatively hypothesized that DG3K,PARS2 and RPE play a key role in regulating the heat tolerance of tomato.4.Bioinformatics analysis of the DG3K gene revealed that the protein encoded by the DG3K gene consists of 415 amino acids;the protein is mainly localized in the mitochondria;it is mainly composed of four structures:α-helix,extended chain,β-turned angle and irregularly coiled;according to the comparison of homologous proteins between different species,the tomato DG3K protein is in the same family as potato and is the closest relative.