Studying Of The Effect Of Salinity On Photosynthesis And The Mining Of Salt Tolerance Gene In Maize (Zea Mays L.)

Salinity in soils is a major global problem and is one that is of growing importance. Maize （Zea mays L.） is one of the most important cereal crops in the world, which production is limited under abitotic stresses like drought and salt. Maize is grown widely in the world with moderate sensitivity to salinity. The most effective approach to improve maize salt tolerance is breeding salt tolerance varieties. Cloning genes related to stress tolerence in maize not only shows theoretical meanings, but also benefits to practical application, providing potential candidate genes for improving stresses torlerance by genetic transformation in maize. A recombinant inbred lines （RILs） population of 364 lines derived from all over the world was used to conduct the effect of salinity on photosynthesis and relative gene cloning for salt tolerance in maize. The main results are following:1. The salt tolerance of 364 inbred lines were identified in maize, and four resistant material and sensitive material were screened. We have shown substantial differences in the responses of the photosynthetic apparatus of two maize inbred lines to salt stress. The salt tolerance of maize seems to be associated with a less accumulation of Na+. PSII was more sensitive to salt stress than PSI.2. In this study, the survival days and the ratio of dead leaves under salt stress in maize were the selection index.364 inbred lines of maize and 558000 SNPs were used to conduct genome-wide assoiciation study. Four SNPs loci （P<1.8x10-6） are significantly related to the survival days and the ratio of dead leaves. The P value reaches 9.36x10-6 of chromosome 5, which reliability is larger, so this article focuses on chr5.S₂594592 marker of chromosome 5.We obtain six candidate genes through scanning chromosome 5 which linkage disequilibrium was 100 kb.3. In order to understand the expression level of six candidate genes obtained through genome-wide association study （GWAS） under salt stress, Real-time PCR analyses were performed to determine the expression of salt tolerance material and sensitive material. The results showed that the expression of GRMZM2G110881 was 35 folds of the control under salt treatment. GRMZM2G406974 cannot express under salt treatment, and the expression of the other four genes had no significantly differance between control and salt treatment. We guess that GRMZM2G110881 may be related to salt tolerance. The full length cDNA of GRMZM2G110881 gene was obtained through in cloning method. The results of bioinformatics analysis show that it encodes 331 amino acids and belongs to short-chain dehydrogenases/reductases family, and showed high identity with other SDR in plant.