Evaluation Of 26 Melon Varieties Against Salt Tolerance And Study Of Mitigating Effects By Exogenous NO Application

In recent years,unreasonable irrigation and excessive fertilization in the development of facility agriculture have increasingly aggravated the problem of soil secondary salinization,severely inhibited the growth and development of crops,resulting in a decline in yield and quality,and affecting planting efficiency.Melon（Cucumis melo）is an important economic crop for facility horticulture,and it also faces the harm of soil salinization in its production.Cultivating salt-tolerant varieties of melon and alleviating the adverse effects of salt stress through technical measures are the main research contents to solve the problem of melon cultivation in current facilities.In this study,26 different melon materials were evaluated for their salt tolerance,in order to screen out the melon varieties and germplasm with strong salt tolerance,and lay the foundation for the breeding of salt-tolerant varieties and seeds for production.At the same time,the effects of exogenous NO on the growth,antioxidant system,mineral element absorption and fruit yield and quality of thick-skinned melon’Nongdatian 10’under salt stress were studied,providing theoretical basis for the physiological mechanism and technical application of exogenous NO in alleviating salt stress of melon.The main results are as follows:1.Divide the 26 melon materials into four categories:5 extremely salt-tolerant materials,11 salt-tolerant materials,6 medium-salt-tolerant materials,and 4 salt-sensitive materials.2.Exogenous NO significantly alleviated the inhibition of salt stress on melon growth.With the increase of SNP（NO donor）concentration,the mitigation effect showed a trend of first increase and then decrease,and 100μmol/L SNP treatment had the best effect,and the plant height,stem diameter,leaf length,leaf width and seedling index of melon were increased by 39.36%,27.49%,19.37%,13.66%and 45.52%,respectively,compared with the water control.3.Exogenous NO can effectively improve the activities of antioxidant enzymes（SOD,POD,CAT,APX）in melon under salt stress,and significantly reduce the contents of hydrogen peroxide（H₂O₂）,superoxide anion（O₂^-）and malondialdehyde（MDA）and relative conductivity,100μmol/L SNP in the range of 50-250μmol/L has the best effect,and the effect is reduced when the concentration is too low or too high.4.Exogenous NO regulated the balance of mineral elements in melon plants.Under Na Cl stress,the content of Na in roots,stems and leaves of melon increased significantly,and the contents of mineral nutrients such as Ca,Mg,N,P,and K were lower than those of normal plants.NO could increase the content of Ca,Mg,N,P,K in different parts of melon root,stem and leaf under salt stress,and reduce the content of Na element,the effect of 100μmol/L and150μmol/L SNP treatment is obvious.5.NO can significantly improve the yield and quality of melon.Under the optimal concentration of 100μmol/L SNP treatment,the melon fruit longitudinal and transverse meridians and pulp thickness increased,the yield increased by 65.74%,and the quality indicators of soluble solids,soluble protein,soluble total sugar,reducing sugar and vitamin C were improved respectively.27.04%,14.26%,25.37%,53.93%,38.79%.