Establishment Of Salt Tolerance Evaluation System Of Medicago Sativa L.and Analysis On Salt Tolerance Mechanism

In order to study the salt tolerance of alfalfa,this thesis constructed a stable alfalfa salt-tolerant experimental evaluation system,evaluated the salt tolerance of multiple alfalfa varieties,and screened out salt-tolerant varieties and salt-sensitive varieties,and their preliminary research has been done on the salt-tolerant mechanism.The results of the study are as follows:（1）The relevant indicators of the germination period of 30 alfalfa seeds of different varieties were measured and analyzed.According to the comprehensive evaluation results of the membership function,they were divided into three categories:salt tolerance,moderate salt tolerance and salt sensitivity.Among them,Zhongmu No.1 has the strongest salt tolerance and Longdong alfalfa has the weakest salt tolerance.Select 4 salt-tolerant varieties（Zhongmu No.1,Queen alfalfa,Longmu 806,Grassland No.2）,3 moderately salt-tolerant varieties（4010,Longmu 803,Suntory）and 3 salt-sensitive varieties from the material library（Xinjiang Daye,WL323,Longdong Alfalfa）were evaluated for salt tolerance at the seedling stage,and the results showed that Zhongmu No.1 had the strongest salt tolerance and WL323 had the weakest salt tolerance.A joint analysis of the evaluation results of salt tolerance at the germination and seedling stages showed that the salt tolerance rankings of different materials were inconsistent at the germination and seedling stages.（2）Salt stress,alkali stress,and mixed salt-alkali stress were performed on Zhongmu1 and WL323,and their photosynthetic index changes under different treatments and the expression changes of related genes under the salt stress signal pathway were analyzed.The results showed that under saline-alkali stress,the leaf photosynthetic rate of Zhongmu1 and WL323 increased with the number of stress days,the F₀change showed an upward trend,and Fm and Fv/Fm showed a downward trend.Semi-quantitative RT-PCR analysis was performed on the roots of alfalfa.Six genes CIPK10,GS,APX2,SOD-Fe,WRKY4 and NAC37 were all expressed after stress.（3）Bioinformatics analysis of the CIPK gene family of Zhongmu No.1 showed that there were 28 members in the CIPK gene family of Zhongmu No.1;the cluster analysis results showed that the CIPK of Zhongmu No.1 was divided into 5 sub-families.The structure of most genes in the same group is similar;the results of phylogenetic tree analysis showed that the genetic relationship between Zhongmu No.1 and Medicago truncatula was the closest.The cis-elements of the promoter are mainly related to light response,auxin and stress response.