| Soil salinity is one of the most serious environmental and social economical problems around the world, therefore to reveal the mechanism of plant salt resistance has great directive significance for the exploitation and utilization of saline soil resource and the development of saline water irrigation agriculture. Research has shown that different varieties of one crop have different salt resistance capacity. Moreover, melon, which is a middle salt tolerance crop, has the potential to be a crop resource of salt tolerance and high yield. The objective of this study is to establish a system which can evaluate melon?s salt tolerance index by analyzing salt tolerance capability and physiological index of different stages of melon varieties and screening out the higher salt tolerance melon variety.The research were departed into three experiments as follows. First experiment used36 melon varieties as materials, with 0,75,150,225,300mmol/L NaCl concentrations as treatments to investigate the salt resistance mechanism of melon in germination stage, in order to investigate the effect of different salt concentrations on melon seeds germination, screen out higher salt tolerance melon variety and confirm the appraisal indexes of melon in germination. Second experiment was carried out based on results of the first experiment. 8 varieties including 4 salt tolerant and 4 salt sensitive were selected and treated with five salt concentrations, the same as the first experiment. And the effects of different salt concentrations on melon seedling growth and physiology were inspected. At last, 2 salt sensitive and 2 high salt tolerant melon varieties chosen in the second experiment were used for the maturation stage experiment with same treatment as before, meanwhile the yield, fruit quality and Na~+/K~+ content of melons were analyzed. The results showed as below: Melon variety named ?Bingxuecui? was screened out of 36 varieties as and relative salt tolerant variety and ?Yulu? as the relative sensitive one after germination stage, seedling stage and maturation stage experiments via Self-Organizing Map analysis. And three experiments showed that melon in different growth stages had different salt tolerance capabilities, though the differences were not so significant. Moreover, the 150mmol/L-225mmol/L salt concentrations could show the salt tolerance capability differences better among melon varieties. With 75mmol/L salt treatment, some fruit quality parameters, such as soluble solid content, soluble sugar content and Vc values were improved. However, the fruit quality was declined obviously at high salt concentration, accompany with nitrate accumulation. The correlation analysis and principal component analysis indicated that the germination energy, germination rate and germination index made larger contributions to the salt tolerance in germination stage of melon. While the shoot fresh weight, root fresh weight, total fresh weight and soluble protein content had larger contributions to the salt tolerance in seedling stage of melon. And, yield, Na~+ content of leaves, and Na~+/K~+ of leaves possessed larger contributions to the salt tolerance in maturation stage of melon. Hence, these indexes could be regarded as important appraisal indexes to assess salt tolerance of melon of corresponding stage.In the last experiment, salt tolerant and sensitive varieties shared same principle that Na~+ content and the value of Na~+/K~+ of root, stem, leaf and fruit of increased significantly while the K~+ content decreased significantly as salt concentration raised,. Nevertheless, some significant differences were found between them. The Na~+ content in leaf of salt tolerant varieties had outstanding lower lever than salt sensitive ones, and K~+ decreasing amplitude and Na~+/K~+ of salt tolerance was less than sensitive varieties. Na~+ content of different organs ranked as follows, stem > leaf > root = fruit, K~+ content of fruit was more than stem, and fruit had the lowest Na~+/K~+ ration.. Keywords: Melon(Cucumis melo L.); NaCl concentration; Salt tolerance capability; Clustering analysis; principal component analysis; fruit quality; Na~+/K~+... |
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