Studies On The Inheritance & Physiological And Biochemical Characteristics Of Watermelon Resistant To Fusarium Wilt

Fusarium wilt ( Fusarium oxysporum f. sp. Niveum) is one of the most destruction diseases which is hard to cure when infected.The most effective and economical way was to use the resistance inherent in the plant.Seven varieties with the different degree of resistance to Fusarium wilt, which were used aboard in international and excellence plant in China were taken as the investigate object to deal with the inheritance of resistance and some physilogical-chemical changes on disease resistance in watermelon infected with Fusarium wilt disease.In order to study the disease resistance mechanism and laid a foundation for further study.At the first, seven inbred cultivars with variant resistance were selected to make the crosses according to Griffing′s diallel methodⅡand 28 F1s were obtained to analyze the inheritance of resistance to get some achievement. Analysis of the relative genetic parameters showed that resistance to Fusarium wilt in a complex way and is controlled by recessive polygenes, and there were additive -dominance effects between major genes.The analysis of Wr+Vr showed that the additive effect was major and the susceptibility was partially dominant.The inheritance of resistance in the highly resistant accessions(Calhoun Gray,Sugerlee) to race1 conform to a single dominant gene conditioned the resistance and there was significant correlation between the genes controlling the characters. The moderately resistant ones (Charleston Gray) and light resistance ones (Xinkang-♀,Hong5-2) resistance to Fusarium wilt in a complex way.The second, the dynamic changes in membrane permeability, activities of some enzymes, and content s of some chemical compounds in the roots and leaves cell of different watermelon cultivars were studied after they were infected by Fusarium ox ysporum f .sp. niveum at seedling stage. The results showed that the activities of malonaldehyde (MDA),superoxide dismutase (SOD) content and relative electrical conductivity cotyledons inoculated with Fusarium ox ysporum f .sp. niveum have close negative correlation with the resistance of watermelon cultivars in roots or leaves of watermelon in the cotyledons.And the activities of peroxidease (POD) content have close correlation with the resistance. Resistant cultivars,compared with susceptible cultivars,display low range of malonaldehyde (MDA),activity and membrane lipid peroxidation and relative electrical conductivity between treatment and control. The activities of peroxidease (POD) content, resistant cultivars compared with susceptible cultivars,have a more quickly flood tide which is durative more time and display high range of peroxidease (POD) activity between treatment and control. There were changes in the peroxidease (POD) isozyme bands of inoculation among different cultivars.Isozyme bands of resistant cultivars are stronger than susceptible cultivars,compared with respective control. And a new isozyme bands come forth in some resistant cultivars. Changes of the activities of superoxide dismutase (SOD) and catalase (CAT) in a complex way after inoculation, resistant cultivars compared with susceptible cultivars, display low range of superoxide dismutase (SOD) and CAT activity between treatment and control The results showed that the capacities of self-regulating and returning to normal status of resistant cultivar , were stronger than susceptible one , in content of malonaldehyde (MDA) , relative conductivity , and activities of superoxide dismutase (SOD) and catalase (CAT) , when they were infected by Foxysporum f .sp. niveum. The result showed that the content of the soluble protein rose at first and then dropped later in susceptible varieties, but the content of the soluble protein dropped at first, and then rose in resistant varieties after inoculation.