Research Of Root System Characteristics And The Relationship Between Roots And Cold Tolerance In Alfalfa Cultivars

A study was conducted to determine the crown, root system characteristics , the correlation analysis of index in root system, the principal component analysis, the root system morphology cluster analysis, the winter survival rate, the correlation analysis of index in crown diameter,crown depth and winter survival rate, the frosted symptoms of the over-wintering, POD activity for different alfalfa varieties,etc,of thirteen alfalfa with different origins1 The reselt indicated that there was significantly difference of the character of crown in cultivars,The crown diameter, crown depth was greatest in Maverick, there was no significantly difference in crown branch. There was significantly difference of the character of root system in cultivars, Zhaodong has the longest tap root(16.5cm)and lateral root diameter(0.33cm), Maverick has the greatest tap root diameter(0.63cm) and lateral root number(4.6), lateral root position was greatest in Gongnong No.1(3.9cm), the indexes in all over the alfalfa cultivars were significantly higher than all of the others.2 Correlation analysis indicated that,except for the tap root length and lateral root position,other indexes of root including crown diameter, tap root diameter, lateral root number, lateral root diameter was significantly or high significantly positive correlation, the correlation among the tap root length and lateral root position with other indexes was not significant. Principal component analysis indicated that the frist component contribution rate is 46.4190%,it is main aspects,the next is root diameter and tap root length, contribution rate is 20.9041% and 17.9611%. The root system morphology cluster analysis indicated that the frist root system morphology similar,including Maverick and Gongnong No.1,the second including Caoyuan No.3, Zhongmu No.1, Zhaodong, Keqihuanghua, Aletai,the third including Rambler, Caoyuan No.2, Zhilihuanghua, Legend,CUF101,the last one is Zhungeer.3 Cold_tolerance analysis indicated that the varieties with strong cold resistance were Maverick, Caoyuan No.3, Caoyuan No.2.The varieties with medium cold resistance were Keqihuanghua, Gongnong No.1, Zhilihuanghua, Aletai, Rambler, Zhaodong, Legend.The varieties with weak cold resistance included Zhongmu No.1 and Zhungeer. The varieties with weakest cold resistance was CUF101, winter survival rate was 35%.The correlation analysis of index in crown diameter,crown depth and winter survival rate indicated that the crown diameter,crown depth and winter survival rate was significantly or high significantly positive correlation.4 The POD activity was significantly different among alfalfa varieties under cold stress.The POD activity of Keqihuanghua was stronger than that of the others, secondly was Maverick, Caoyuan No.3, Zhilihuanghua, Caoyuan No.2. Zhungeer and CUF101,showing their cold resistance were weakest,the others suggesting the medium cold resistance.