Tomato Helminthosporium Carposaprum Infection Mechanism Of Preliminary Study

In this study,electron microscopy of tomato Helminthosporium Carposaprum infection process,Wax and Cutin layer of tomato in Relation to Infection by Helminthosporium carposaprum,Infection factors and pathogenicity of tomato Helminthosporium Carposaprum pathogens,The kinds and activity of cell wall degrading enzymes produced from tomato Helminthosporium Carposaprum pathogens, Changes of protective substances and protective enzymes in the interaction of tomato and Helminthosporium carposaprum,Transmission and infection cycle of tomato Helminthosporium carposaprum pathogens,the main results were as fo11ows:1. By electron microscopy results show that the pathogen was able to penetrate host through three paths such as epidermis,stomata and intercellular space 12~24h after inoculation.intercellular space was considered as a major way.After invading into the tomato leaf tissue,the pathogen spread ntercellularly and then formed intracellular hyphae in the necrotic host cells.As the extension of the hyphae,a series of cytopathological change occurred in the host tisse, including plasmolysis,degeneration of organell such as chloroplast and vacuoles, the generation of crystalline lens,photorespiration. hese results indicate that cell wall-degrading enzymes are closely related to the penetration and extension of pathogen.2. When the Wax in tomato leaves was removed with chloroform or the cutin layer was removed with KOH or cutinase,fungal infection rate in tomato leaves, was significantly increased. There was no significant difference in Helminthosporium carposaprum infection rate between leaves whose wax and Cutin within were removed at the same time and leaves damaged by pin puncturing,indicating that the major anti-disease components in leaves were wax and cutin.Wax extract in leaves antibacterial effect was not significant in vitro.Wax resistance role is mainly to prevent physical penetration Helminthosporium carposaprum.3. Infection factors and pathogenicity of Helminthosporium carposaprum have shown that temperature and wetness period greatly affected the infection of Helminthosporium carposaprum. When temperature was 10℃,the incubation period was 120 h.When temperature was from 25℃to30℃,the incubation period was only 74h.The least wetness period was about 6h.The favorite combination of temperature and wetness period for infection was that temperature was from 25℃to 30℃and wetness period from 42h to 48h.The susceptibility tests of different varieties of tomato to Helminthosporium carposaprum indicated that 704,7929,7913 were susceptible varieties of tomato.08HN31,7945,08HN30 were resistant varieties of tomato .The pathogenicity tests of different period isolates showed that 10 d was the strongest.4. A series of cell wall degrading enzymes (CWDEs) including pectin methylesterase( PE ) ,polygalacturonase(PG),polymethylgalacturonase( PMG) ,polygalacturonic acid transeliminase(PGTE),pectin methyl transeliminase(PMTE),and Cx were found in tomato Helminthosporium carposaprum pathogens. Results from enzyme dynamics analysis showed that different kinds of CWDEs had special optimum temperature,pH and reaction time of their maximum activities.For example , PG,PMG, and Cx as a hydrolytic enzymes showed maximum activities at pH 5.0,and 50℃; PGTE和PMTE as a lytic enzymes at 9.0 and 30℃. The activity of PG, PMG, PGTE,PMGE,Cx increased greatly with the day in vitro,but in vivo CWDEs showed higher activities as compared with those in vitro.5. The results showed the rate of O2-production were higher in the resistant cultivars than that in the susceptible cultivars, and the peaks of O2- appeared at18h.However,in the susceptible cultivars,the rate of O2- production were lower or similar to control. The SOD,POD activities in the susceptible cultivars were usually higher than that in the resistant cultivars, At 24h,the CAT activities in both interactions were all higher than that in control,and CAT activities in the susceptible cultivars were higher than that in the resistant cultivars at 36~48 h,but after 48h CAT activities in the susceptible cultivars were lower than that in the resistant cultivars again.6. Inoculated after the leaves of resistant cultivars,MDA levels began to rise,and slightly higher than the control;in the leaves of susceptible cultivars,MDA levels were lower than the control or the control near. From the average point of view,two varieties of processing increased soluble sugar content than that of control,While the Vc content and soluble protein content decreased compared with control;After treatment, resistant cultivars of soluble sugar content and soluble protein content were higher than the susceptible.7. Sudies on the trannsmission of tomato Helminthosporium carposaprum had been carried out that it is mainly transmitted by the soil and debris which naturally infected with pathogen.The seeds can be infected however ,low incidence .