Study On Comparison Of Different Melon Varieties Tolerance To Salt Stress

Melon（Cucumis melo L.）is one of the widely cultivated vegetable crops in the world.With the expansion of protected cultivation area,the increase of planting years and unscientific fertilization management,the salinization and secondary salinization of protected soil are becoming more and more serious,which became the factor of limiting melon production.In this experiment,the effects of different concentrations of NaCl stress on melon seed germination,plant morphology and physiological indexes at seedling stage were studied,and the evaluation indexes of salt tolerance indexes at germination stage and seedling stage was established by using the methods of correlation analysis,principal component analysis,membership function analysis and systematic clustering,the purpose was to select the melon variety tolerance to salt stress.The main research results are as follows:With the increase of NaCl concentration(0～250 mmol·L^-1),the germination rate,germination potential,germination index,plant height,root length,aboveground fresh and dry weight and underground fresh and dry weight of different melon varieties generally showed a downward trend,while the salt damage index continued to rise.Under the concentration treatment of 0 mmol·L^-1,150 mmol·L^-1and 200 mmol·L^-1,compared with the control,the strong seedling index,chlorophyll and soluble protein content of melon varieties with strong salt tolerance decreased slightly,the activities of SOD,pod,cat and proline increased significantly,the induced malondialdehyde content was less,but the root activity increased;The suitable stress concentrations of melon germplasm resources at Germination and seedling stages were 150～200 mmol·L^-1.The salt concentration of 200 mmol·L^-1was selected as the screening and evaluation of salt tolerance of melon germplasm during germination and seeding stage.The comprehensive membership function value of salt damage coefficient of each index was obtained.Through cluster analysis,during germination,21 strong salt tolerant varieties,50 salt tolerant varieties,69 medium salt tolerant varieties and 67 salt sensitive varieties were selected from 213 melon germplasm;At the seedling stage,10 muskmelon germplasm were divided into three grades:5salt tolerant varieties,2 medium salt tolerant varieties and 3 salt sensitive varieties.Through comprehensive analysis of salt tolerance in germination and seedling stage,4 relatively stable salt tolerant varieties were selected.Using principal component analysis,it can be determined that germination index is the most important index for the identification of salt tolerant varieties in melon germination period,and vitality index,germination potential and embryo length are the important indexes for the identification of salt tolerant varieties in melon germination period;Plant height,aboveground fresh weight,aboveground dry weight and CAT activity are the most important indexes for the identification of salt tolerant varieties in melon seedling stage.Root length,underground fresh weight,underground dry weight and POD activity are the important indexes for the identification of salt tolerant varieties in melon seedling stage.