Studies On Low Temperature Stress Resistance And Some Physiological And Biochemical Indexes And Genomic DNA Methylation Of Alfalfa

Alfalfa has good grass quality and high yield.In recent years,it has been widely cultivated and popularized in northern China,but the overwintering rate of alfalfa has become the main problem because of the cold winter in the north.With the increasing demand of alfalfa and other forages,scientific research on low temperature stress of alfalfa and breeding of cold resistant and high-yielding varieties are of great significance.In this study,In order to explain their relationship with Overwintering Rat e and yield from molecular level and morphological characteristics,8 alfalfa v arieties with different cold resistance were tested at different low temperatures to determine the level of DNA methylation,chlorophyll fluorescence parameter s,soluble protein content,soluble sugar content,amino acid content and the m orphological characteristics of plant ground.The results showed that the Overwintering Rate of Alfalfa Varieties with relatively high stem-leaf ratio and yield was relatively high;Under the high temperature,the Fo value increased and decreased with different temperatures,and the Fm and Fv/Fm value decreased significantly.The maximum mean value of soluble protein content and soluble sugar content appeared at the lowest temperature in December,and the lowest values appeared in May and 4 respectively.The higher the soluble protein content in March,the higher the Overwintering Rate of alfalfa and the higher the yield.In September,the higher the soluble sugar content was before winter,the higher the Overwintering Rate of alfalfa.2006-YL-2 was significantly different from the other 7 varieties,and the average content of soluble protein and soluble sugar in cultivar 2006-YL-2 was the highest during the whole low temperature exercise;The highest values of all contents appeared in May after turning green,and the lowest appeared in the lowest temperature in December;There was a significant or very significant correlation between the four amino acids of SER,MET,ALA and ARG and wintering rate,These results suggest that the changes of these 4 amino acids may play a regulatory role in Alfalfa during low temperature exercise;With the decrease of temperature,the DNA methylation level of Alfalfa increased,and the methylation level decreased first and then increased with the increase of temperature.