Comprehensive evaluation of high temperature and high heat resistance of 22 Medicago sativa L.varieties
The study aimed to screen out new varieties(lines)of heat-resistant alfalfa(Medicago sativa L.)that are suitable for cultivation in the southern regions,this study selected 22 different varieties(lines)of alfalfa with varying levels of dormancy as experimen-tal materials,and used pot cultivation method to explore the effects of heat stress on their growth and physiological characteristics.The heat tolerance of these varieties(lines)was comprehensively evaluated using membership function and clustering analysis.The results indicated that the physiological characteristics of 22 alfalfa varieties were impacted to varying extents by increasing stress temperatures.Through clus-ter analysis and membership function evaluation,all materials were categorized into three groups:strong heat resistance,moderate heat re-sistance,and thermal sensitivity.Among them,the strong heat resistant type includes Nanmu 701,WL525HQ,and Sardi 10,the ther-mal sensitive type includes Nanmu 801,Sardi 7,and Victoria,and the rest of the materials are medium heat resistant.Selecting the strong heat-resistant material Nanmu 701,the medium heat-resistant material Ghillie,and the heat sensitive material Nanmu 801 for physiolog-ical index analysis,it was found that heat stress had the smallest impact on the strong heat-resistant material Nanmu 701,the smallest de-crease in relative water content in leaves,stable changes in electrical conductivity and malondialdehyde,a large accumulation of osmoregu-latory substances such as soluble sugars content and proline.The activities of antioxidant enzymes such as catalase,superoxide dismutase,and glutathione peroxidase were significantly higher(P<0.05)than other materials.The research results provide reference for the promo-tion of new varieties of purple alfalfa suitable for planting in southern regions.