Lnfection Simulation And Bioassay Of Different Squash Cultivars'Physiological Lndicators In Lnteraction With P.capsici

Squash blight disease is a disease which is caused by P. capsici, and also one of the most destructive diseases in Heilongjiang Province. A systematic studies were carried out and determined at three different levels. One aspect was simulative infection of the pathogen, another was epidemiology forecasting of the disease and the dynamic changes of physiological indicators (POD, PPO, PAL) in squash stems infected by P. capsici. The results showed: Under manual control, the studies analysised the influence of temperature, content of soil water and both of them on the incident of squash blight .The incident of squash blight increased with increasing temperature up to about 30 t, and then declined. Optimum temperature for infection was between 26Cand 30 C.Successful infection required at least 40% content of soil water and more than 80% content of soil water, incident was lOO%.A regression model using the incident as the dependent variable accurately described infection level as a function of temperature and content of soil water. The infection percentage model as follow: SQRT(I)l.38l.l33X1O DT.588XlOXSW-s-5.133xlO3xDTx SW.232XlO DTxSW+2.O93Xl0xDT2+8. l94XlOSW R0. 9089 F146. 64 ssO. 0268 In which I is incident DI is temperature SW is water contain in soil. By systematic survey of squash blight caused by P capsici in1997999. The results showed that Logistic model was the best one for simulating the disease progress curve. Busing primary disease incidence and several climate factors predicting the model for apparent infection rate was developed as follows r8.Ol+2. 14XT+0.496XRQ.21OXRD .O73XLn[tl/(ll)].083XT2+0.0036 XTXRD2-O. 0005XTXRH2+0. OOI3XT2XRH. 0168XRQ2. O57XRDXRQ+0. 0069XRH2 R0. 99772 F1948. 33 ssO. 0135 In which r is the apparent infection rate . T is dialy mean temperature . RH is relative humidity and RD is rain day. The activity of POD. PPO and PAL had close relation with the resistant or susceptible squash cultivars. The activity of POD and PPO wasn t distinctly different between the healthy stems of resistant cultivars and the susceptible one, and theactivityofPALwasdistinctlydifferent.IheactivityofPODemerged three higher points in 36h. 48h. 6Oh after inoculation, the activity of PPO emerged two in 30h. 42h after inoculation., the activity of PAL emerged two in 30h . 48h after inoculation. The inoculation stems of susceptible cultivars have similar PPO. POD isozyme bands to the healthy one. The inoculation stems of resistant cult ivars have two more POD isozvme bands and three more PPO isozvme bands than the healthy one of resistant cultivar. The healthy stems of resistant cultivars had similar isozyme hands to the healthy one of susceptible cultivars. The inoculation stems of resistant cultivars had three more POD isozyme bands and three more PPO isozyme bands than the one of susceptible.Name:Zhang junhua Specialty: plant pathology Tutor: Vice Pro. Wen Jingzhi Pro.Jia. Wenxiang...