Functional Verification Of Maize Salt-tolerant Candidate Genes And Establishment Of Salt-tolerant RILs

As one of the major abiotic stress in maize production process,salt stress cause serious damage to the growth,development and production of maize.The tolerance of different maize lines to salt stress is significantly different,but the genetic basis for this phenomenon is largely unknown.Understanding the genetic basis of maize salt tolerance is beneficial to the development of maize breeding for salt tolerance.In this project,we analyzed the genetic basis of salt tolerance of maize genetic population by genome-wide association analysis and transgenic verification.The effects of natural variation on salt tolerance of maize seedling were verified by constructing recombinant inbred lines.In the previous study,7 genes were selected as candidate genes via combined genome-wide association analysis and linkage analysis and named Zm SAGs.Among them,Zm SAG4 encodes SEC23 protein,which is mainly involved in the protein transport in the endoplasmic reticulum and plays a very important role in alleviating ER stress.Another gene is Zm SAG6,which encodes MRE11 protein and plays a very important role in the repair of plant DNA damage caused by salt stress.We overexpressed these two genes in Arabidopsis,and the transgenic material showed more tolerance to salt stress in seed germination and growth development than the wild type,and also accumulated more proline in cells.Hence,they can be considered as a positive regulator of salt stress response.Via candidate gene associated analysis,we detected 7 SNPs located in Zm SAG4 associated with salt stress,including C allele of SNP3341 and G allele of SNP3583.The population has two favorable allelic variations,and haploid type 4 showed significant tolerance to salt stress(p < 0.01).The SNP-781 and SNP-4051 in Zm SAG6 located in the upstream of the initiation codon were the most significant sites affecting salt response in the population.Hap1 and Hap 4 obtained from these two sites showed more tolerant to salt stress.In addition,we constructed recombinant inbred lines derived from the cross between HZLY-1(extreme salt tolerance)and HZS(extreme sensitivity),which called HH population.Resequencing in HZLY-1 and HZS revealed an In Del in Zm SAG4 3'UTR that significantly associated with survival rates of maize after salt stress.Then,we collected the plant height,biomass,and the survival rate after salt stress.It is hoped that thislinkage population can be used to validate the above In Del,and can be used to map other potential genetic loci of salt tolerance.This study verified the salt-tolerance of two candidate genes and their favorable alleles,constructed a RIL population based on salt-tolerant and-sensitive parents.Our results provided genetic materials and potential gene and marker resources for maize salttolerance study and breeding.