| Seed vigor declined during storage, and seeds germination might be subjected to various adversities in the field, such as drought, humid and cold, which causing low germination rate and weak seedlings. However, seeds with high vigor showed high resistance to adversities, good growth potential and high productive potential. In the field, sowing seeds with high vigor palys an important role in agricultural production. Therefore, it is of reference value to further understand the biochemical and molecular basis of seed vigor by studying wheat seed vigor and the differences in related enzymes activities and genes expression under stress conditions.The vigor indexes of 16 wheat cultivars were measured by standard germination test, field emergence test, artificial aging, cold soaking and drought stress test in the present study. The comprehensive evaluation of wheat adversity resistance index of vigor index of artificial aging, cold soaking, drought stress and field emergence percentage of sixteen wheat cultivars were conducted with principal components analysis and cluster analysis. High vigor and low vigor wheat cultivars were filtrated, then soluble sugar content, soluble protein content, α-amylase activity, cysteine protease activity and gene expression of two kinds of different vigor levels were measured in the experiment. This study aimed to analyze the main related enzymes activities and gene expression differences in different genotypes of wheat cultivars, and cleared the relationship between the main related enzyme activities and seed vigor or gene expression under stress germination. The main findings were as follows.1. Resistance evaluation of wheat cultivars seed germination under adversity stressThe vigor indexes of 16 wheat cultivars were measured by standard germination test and adversity test in the present study. The adversity resistance index of vigor index and field emergence percentage of 16 wheat cultivars was measured as physiological indexes for evaluating the adversity resistance. Based on principal component analysis and cluster analysis, 16 wheat cultivars were divided into 3 groups. Seven cultivars, Yunong 949, Yumai 49-198, Luyuan 502, Zhengyumai 9987, Shimai 21, Shannong 23, and Shixin 828, belong to high vigor group; seven cultivars, Xunong 5, Yunong 982, Tangmai 8, Jimai 20, Jimai 22, Jinan 17, and Shannong 20, belong to medium vigor group; the other two cultivars, Chang 4738 and Lunxuan 061 belong to low vigor group. The seed vigor can be evaluated comprehensively with the comprehensive evaluation value(D value) of the resistance of 16 wheat cultivars.2. Changes of the a-amylase and cysteine protease activities, expression levels, storage substance content during the germination of wheat seedsWith the prolongation of germination time, a-amylase activity showed a trend of rising as a whole, cysteine protease activity showed a trend of decrease at first and then increase as a whole; soluble sugar content showed a trend of small amplitude increase at first and then small amplitude decrease and then increase rapidly, soluble protein content showed a trend of gradual decline, α-AMY expression levels showed increased at first and then decreased trend as a whole, CP expression levels showed a rising trend as a whole, but expression levels of different treatment of different cultivars have the respective characteristics under standard germination, drought stress artificial aging and cold soaking stress.3. Correlation between the a-amylase and cysteine protease activities and seed vigor in wheat during seed germinationThe α-amylase activity significantly positively correlated with the vigor index under the standard germination condition. However, the α-amylase activity had no significant correlation with the vigor index under stress germination. After cold soaking stress, cysteine protease activity significantly positively correlated with vigor index in seed germination, but the correlation was not significant in standard germination, drought stress and artificial aging.4. Correlation between the a-amylase and cysteine protease activities and expression levels or soluble sugar and soluble protein contentThere was no direct relationship between the activity of α-amylase and cysteine protease and their gene expression under different germination conditions. The α-amylase activity and soluble sugar content were extremely significant positive correlation, and the correlation between cysteine protease activity and soluble protein content was not significant. |
