QTL Mapping Of Salt Tolerance In Maize Seedling And Functional Verification Of Candidate Gene

Maize(Zea mays L.)is one of the major food crops in China,which plays an important role in food safety.With the aggravation of soil salinization,the total area of salinized land in China has reached more than 200,000 square kilometers,which has become one of the main constraints on Chinese agricultural development.Maize is known as a salt sensitive species,it is more feasible to solve the salinization problem by breeding high-salt resistant varieties than by soil amendment.It is of great significance to excavate genes involved in salt tolerance,which not only helps us to understand the underlying molecular mechanism of salt resistance in maize,but also provides gene resources for salt tolerant maize varieties breeding.In this study,160 recombinant inbred lines derived from two parents with significant difference in salt tolerance and 316 inbred lines provided by Huazhong Agricultural University were investigated by the survival days of maize seedling under high salt treatment.In addition,one candidate gene,verified in our previous study and this study,was cloned and transformed into rice for further confirmation.The main results are as follows:1.160 maize inbred lines were treated with 200 mM NaCl in the three-leaf-and-one-leaflet stage.The survival days of the seedling under salt treatment were taken as the salt tolerance index.The QTL linkage analysis was carried out by combining the bin map genetic map constructed by 20K genotype marker.Two significant QTLs were detected in two years' environments.There is a main effect QTL on chromosome 1,qSD-1,and its LOD value was 15.7,which can explain 35.73%of the phenotypic variation.qSD-9 on chromosome 9 was detected in one environment,the LOD value of this QTL reached 3.09,and the explained phenotypic variation was 4.57%.2.Genome-wide association study(GWAS)for survival days under salt treatment using 316 inbred lines genotyped by 550000 SNP markers was conducted.The results showed that two SNPs,chr5.S 2594448 and chr5.S 2594592,on chromosome 5 were detected using the threshold of-log(P)? 5.745.The phenotypic variations explained by these two markers were 10.63%and 8.34%,respectively.A candidate gene,named GRMZM2G110881,was determined through the LD block analysis.3.The results showed that the expression of GRMZM2G110881 gene may be induced by light,hormone,anaerobic and osmotic stress.To verify the function of GRMZM2G110881,16 T2 generation transgenic lines were obtained,of which 10 positive lines were verified by PCR.Compared to the control plants,three transgenic lines with highest gene expression showed elevated resistance to salt,manifested by higher plant height,more relative water content and lower malondialdehyde content than controls under salt treatment.These results indicated that the overexpression of GRMZM2G110881 could enhance the salt tolerance of rice.