Evaluation Of Low Temperature Tolerance Of 22 Medicago Falcata L.Materials Germplasm

In this study,22 domestic and foreign germplasm Medicago falcata L.were used as materials.Six temperature gradients(25℃,20℃,15℃,10℃,5℃ and 0℃)were set to simulate low temperature stress,and the physiological changes among Medicago falcata L.material under low temperature stress were analyzed,in order to screen out Medicago falcata L.material with better low temperature tolerance and provide scientific basis and theoretical guidance for cold resistance breeding and evaluation of Medicago falcata L.varieties.Main results:(1)Under low temperature stress,22 domestic and foreign Medicago falcata L.were affected to varying degrees.Seven of the eight physiological indexes have changed in different degrees(increase or decrease in price).Among them,the initial fluorescence value(Fo)showed a "down-up" trend.The maximum fluorescence value(Fm)showed a "down-up" trend.The maximum optical efficiency(Fv/Fm)and PSII potential activity(Fv/Fo)showed a downward trend.The soluble sugar content(SS)showed a "rising" trend with the decrease of temperature.The content of malondialdehyde(MDA)and Proline(pro)showed an overall trend of "rising-falling-rising".(2)Through the analysis of phenotypic correlation,it is found that the phenotypes of 22 domestic and foreign materials are influenced by many aspects.Through the correlation analysis of physiological indexes,it is found that soluble sugar,malondialdehyde,proline,Fo,Fm,Fv/Fm and Fv/Fo can be used as physiological indexes of cold resistance.(3)According to the comprehensive evaluation of cold resistance of 22 Medicago falcata L.materials at home and abroad by membership function,the order of cold resistance is H20 > H7 > H21 = H6 > H10 >H3 > H5 = H13 = H15 > H16 > H11 = H18 > H12 = H22 > H1 = H9 > H4 = H19 > H8 > H2 > H17 > H14.