Cold Resistance Evaluation And Index Screening Of Medicago Falcata L.

Medicago falcata is a high protein forage widely distributed in Xinjiang and Inner Mongolia.It has high resisitance bleeding value because of pro minent stress resisitance.In this experiment,12 Medicago falcata germplasm from different areas of Northern Xinjiang were used as materials.The changes of regeneration and physiological indexes under different temperature gradients(-5 ℃,-6 ℃,-7 ℃,-8 ℃,-9 ℃,-10 ℃)and different time gradients(3 h,6 h,9 h and 12 h)were studied.Through the comprehensive analysis,the sensitive spots and cold tolerant germplasm of Medicago falcata in low temperature stress were screened.It provides a certain theoretical basis and technical support for the identification,utilization and protection of Medicago falcata resources,the methods of cold resistance identification and resource screening and identification.The main results are as follows:(1)At different temperature,12 tested materials were affected to varying degrees.Plant height,aboveground biomass rate,underground biomass,branch number,lateral root number and relative conductivity were related to the survival rate after low temperature stress.According to the grey correlation analysis,the plant height is the most relevant index with cold resistance.The most sensitive temperature to stress is-8 ℃.(2)At different time,there is a rising trend in catalase activity,peroxidase activity,proline content,malondialdehyde content,soluble sugar and relative conductivity content.The grey correlation analysis shows that the index with the greatest correlation with cold resistance is catalase activity,and the most sensitive time to stress is 9 h.(3)By fitting the Logistic equation,the low-temperature half lethal temperature of 12 Medicago falcata was obtained.The highest material was XJ09 and the half lethal temperature was-5.57 ℃;The lowest material is XJ03,and the half lethal temperature is-9.28 ℃.The order of half lethal temperature of each material is XJ03<XJ02<XJ01<XJ04<XJ07<XJ06<XJ08<XJ11<XJ05<XJ12<XJ10<XJ09.(4)Through cluster analysis,the materials are divided into four categories according to cold resistance:group I is extremely strong: including material XJ03;Group II is strong: including materials XJ01,XJ02,XJ04,XJ06,XJ07 and XJ08;Group III is weak: including materials XJ05 and XJ11;Group IV is extremely weak: including materials XJ09,XJ10 and XJ12.