| Muskmelon(Cumumis melo.L)is a global fruit,ranking ninth among the top ten fruits in the world in terms of production scale and playing an important role in horticulture.Melon is a warm and heat-resistant crop that requires warm,dry,and sufficient sunlight during its growth and development.Therefore,encountering low temperature and cold damage during early spring cultivation can cause a decrease in melon yield and quality,which can have adverse effects on production.Studying the physiological response mechanism of muskmelon under low temperature stress,identifying and screening high-quality cold resistant muskmelon varieties,has significant agricultural production significance.This study evaluated the cold resistance of 21 different melon materials in order to screen out melon germplasm with strong cold resistance and lay the foundation for the breeding and production of cold resistant varieties.By combining morphological indicators with physiological growth indicators,the cold tolerance of muskmelon was evaluated at various stages of germination,seedling,and field growth.The cold tolerance of each germplasm was preliminarily evaluated through the cold injury index,and then comprehensively evaluated using the membership function.The tested germplasm was classified through cluster analysis.Simultaneously,field comparative experiments were conducted on 21 materials.Field experiments compared the differences between germplasm in plant growth trends,fruit yield,quality,and other aspects,further validating the evaluation results of melon germplasm at the seedling stage.The main conclusions of this study are as follows:1.By comparing and analyzing the cold tolerance related traits of 21 melon germplasms during the germination stage under low temperature stress,it was determined that the relative germination index,relative radicle length,and relative vitality index can be used as cold tolerance identification indicators for melon germination stage.2.After low-temperature treatment,the plant height,root length,fresh weight above and below ground,and dry weight above and below ground of each melon germplasm showed a downward trend;The activities of catalase(CAT),peroxidase(POD)and superoxide dismutase(SOD)varied with melon germplasm;Chlorophyll content decreased,proline(Pro)content and malondialdehyde(MDA)content significantly accumulated,soluble sugar and soluble protein content significantly increased,and relative conductivity significantly increased.The aboveground fresh weight,proline,malondialdehyde,soluble sugar,soluble protein content,and relative conductivity are all significantly correlated with the cold injury index,which can be used as important indicators for screening cold resistant germplasm.3.Combining the chilling injury index with the membership function to evaluate the cold tolerance of melon germplasm.Divide 21 melon germplasm into 3 categories.Among them,cold resistant materials include M311,M317,M312,and M313;Medium cold resistant materials include M315,M316,M131,M314,M102,and M318;Non cold resistant materials include M112,M185,M109,M184,M111,M183,M115,M120,M110,M105,and M118.After low temperature stress,the growth of vine length and stem diameter of melon plants is inhibited,and the overall quality indicators of fruit,such as horizontal and vertical diameter,single fruit weight,soluble solids,soluble protein,soluble sugar,reducing sugar,and vitamin C,show a downward trend;There was no significant change in fruit shape index,seed cavity diameter,and flesh thickness;During the growth stage,M102,M131,M311,M312,M313,M315,and M317 showed significant growth in vine length and stem diameter under low temperature stress,demonstrating good cold resistance,which is basically consistent with the results of the seedling stage. |
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