| Pea(Pisum sativum L.)is a cool-season food legume crop widely grown in temperate regions.It is rich in nutrition and is an important source of protein,starch,sugar,crude fiber,vitamins with low lipid.Heat stress is one of the main abiotic stresses leading to yield loss in plant production.As a cool-season crop,pea is very sensitive to heat stress.The increasing trend of global warming in the future may lead to more frequent and severe heat stress in the growing season of peas.Therefore,it is urgent to screen pea germplasm for heat tolerance and explore its tolerant genes.At present,there are only few reports on the screening of pea germplasm for heat tolerance and the mining of heat tolerance genes in foreign countries,and there is almost nothing in this field in China.In this study,2358 pea accessions from all over the world stored in the Chinese Domestic Crop germplasm Bank were sown in three stages each year for three years,and the heat tolerance screening experiments were carried out for three consecutive years.A reasonable classification standard for pea heat tolerance was established based on the yield related traits.The genetic diversity and population genetic structure of heat-resistant and heat-sensitive accessions were analyzed.Based on the results of three years of heat tolerance screening,extreme heat tolerant and extreme heat sensitivive accessions were obtained,and the field phenotypic,cytologic,physiological and biochemical characteristics of these extremely heat tolerant and heat sensitivive accessions were identified.Xp-GWAS and selective elimination analysis were used to identify heat-resistant candidate genes in combination with high-quality pea reference genome sequenced by de novo sequencing.By constructing heat-resistant and heat-sensitive RIL populations for linkage analysis,and combining with BSA pooled sequencing to explore candidate genes for heat tolerance,this study provided theoretical and practical basis for future research on heat tolerant breeding and heat tolerant mechanism of pea.The main results are as follows:1.2358 pea accessions were screened for heat tolerance for three years.Based on this,a heat tolerance classifications standard for pea was formulated with the average grain weight per plant as the measurement standard,and 13 extremely heat-tolerant and 9 extremely heat-sensitive accessions were screened.These 22 accessions were recommended for future research on heat tolerance mechanism and heat tolerance breeding of pea.2.Based on two sets of SNa Pshot markers,the genetic diversity and population genetic structure of432 pea accessions obtained from the initial screening were analyzed,which revealed that the heat tolerance of pea was related to the type of sowing date,and the heat tolerance related markers were affected by heat stress selection.3.The field phenotypic heat tolerance identification test was conducted for the 22 extremely heat-tolerant and extremely heat-sensitive accessions.The results showed that the yield indexes of extremely heat-tolerant and extremely heat-sensitive accessions,such as biomass per plant,pod number per plant,grain weight per plant and 100-grain weight per plant,all decreased under heat stress compared with the normal condition,but the decline of extremely heat-sensitive accessions was far greater than that of extremely heat-tolerant accessins.The results shown that the effect of heat stress on extremely heat-sensitive accessions was much greater than that of extremely heat-tolerant accessions.The results of cytological,physiological and biochemical heat tolerance identification of 10 outstanding extremely heat-tolerant and extremely heat-sensitive germplasm verified the above conclusions.3.The results of field phenotypic heat tolerance identification of 13 extremely heat-tolerant and 9extremely heat-sensitive accessions showed that heat stress had a great impact on the yield of extremely heat-sensitive accessions;the results of cytological,physiological and biochemical identification of 10 extremely heat-tolerant and extremely heat-sensitive accessions showed that extremely heat-sensitive accessions were more vulnerable to heat stress damage.4.Combined with the methods of XP-GWAS and selective sweep analysis,22 heat-tolerant candidate genes and 2067 heat-sensitive candidate genes were found in 13 extremely heat-tolerant and 9 extremely heat-sensitive accessions.Three new heat tolerance candidate genes,including Psat01G0252000,Psat04G0461400 and Psat06G0020500,were found for the first time,which can be used in pea heat tolerance breeding and its molecular mechanism research.5.Four RIL populations constructed with heat-tolerant and heat-sensitive pea germplasm as parents were used to locate 96,42,161 and 364 heat-tolerant candidate genes,and 28 heat-tolerant candidate genes were obtained after further screening. |
