Effects Of Carbohydrate Reserves Upon The Winter Hardiness Of Alfalfa

The contents of total soluble sugar ,starch and sucrose of main root were measured in Alfalfa under different varieties ,cold-stress treatment,mowing time and sowing time,combining data on overwinter score in field in order to research the effects of carbohydrate reserves upon winter hardiness.The results are as follows:Cluster analysis separated the 38 studied varieties into four winter hardiness clust-ers on the basis of overwinter score,clusterâ… c ontains 19 alfalfa varieties: Durango,WL-232HQ, WL252,WL323,Innovation,Grandeur,Liangmu NO.2,Liangmu NO.5,Liangmu601, Liangmu702,Liangmu900,Hunterriver,Farmer's Treasure,Sweden,Leader and Siriver and so on. Clusterâ…¡contains 10 poor winter hardiness varieties:AC Caribou,WL323ML, AmeriStand,Golden Empress,Runner,Haygrazer,WL323HQ,Favor, AE621 and AE733.Cl- usterâ…¢contains 3 good winter hardiness varieties :Xinmu NO.1,wide leaf alfalfa of Xinjiang,Zhongmu NO.1.Clusterâ…£contains 6 high winter hardiness alfalfa varieties: Grassland NO.1,Longmu 801,Longmu 802,Zhaodong,Aohan and Gongnong NO.1. The contents of total soluble sugar ,starch have high or no correlation with winter hardiness score .There are no Significant variances among High cold-tolerance alfalfa varieties and poor cold-tolerance alfalfa varieties. And there are significant variances among high ,low and mid-cold tolerance alfalfa varieties ,which can be used to distinct the winter hardiness.The total soluble sugar content shows upward trend under natural cooling condition . The quantity of soluble sugar content and its increase rate of alfalfa will affect winter hardiness of alfalfa;The reducing of starch content will increase the content of soluble sugar. Lower content of starch will be helpful for improving the capability of cool tolerance of alfalfa. The total soluble sugar content and starch content never show significant change law under Indoor stress conditions. When research on cold tolerance of alfalfa , simulation of cooling can't replace the role of natural temperature changes.Delaying the mowing time will reduce cold tolerance of"Gongnong NO.1",which has no positive impact on improving cold tolerance of AE702 that can't survive winter in west regions of Jilin province. Various mowing treat were not significantly correlated with the content of soluble sugar of main root of Gongnong NO.1.Early and late mowing treatment will accumulate high levels of total soluble sugar before AE702 survive winter. Mowing treatment can't affect the change trend of sugar and starch'content.Delaying sowing time had no significant effect on cold hardiness of alfalfa varieties"Zhaodong"before August 4 .After that time the winter survival rate will reduce. Which had no positive impact on improving the cold hardiness of alfalfa ,WL-525HQ in Jilin Province. The total soluble sugar content of main root in Zhaodong alfalfa was highest for those materials sowed in the July 21.on the contrary ,that was the lowest for those materials sowed in the August 4. The period of highest starch content was the minimum period for soluble sugar content . The total soluble sugar and starch content of main root for WL-525HQ alfalfa is highest for those materials sowed in the June 17 ,but for those materials sowed in the August 4 was the minimum.For Jilin Province, the selection for alfalfa security winter variety was the key in western region, mowing and planting time were secondary factors. The contents of total soluble sugar and starch of main root in different mowing and sowing time and under different treatment conditions of alfalfa have no significant correlation with the winter hardiness scores in the following year.