Studies On Biological Characters Of Venturia Inaequalis And Differentiation Of Venturia Inaequalis Of Apple In Pathogenicity

Apple scab is one of the most serious diseases of apple in china, which seriously threatens the sustainable development of apple production. However, less work has been done on pathogenicity variation of pathogen and biological characters as well as resistance of hosts .In order to understand this disease characters and the epidemic regularity of apple scab, we carried out the research to pathogenicity variation of pathogen, biological characters and resistance of apple cultivar to apple scab and the main results were obtained as follows:1.Three apple cultivars were individually inoculated with 57 representative single spore isolates of Venturia inaequalis collected from different apple grown areas in China, England and India. Results showed that there was obvious difference in pathogenicity among those testing isolates that could produce different types of disease spots in their size, shape and color on the same inoculation host. There was also obvious difference in pathogenicity even if different hosts were inoculated by the same spore isolate of Venturia inaequalis. Based on the host reaction and cluster analysis of disease severity, the isolates of Venturia inaequalis could be divided into three categories: strong (pathotypeⅠ), intermediate (pathotypeⅡ) and weak pathogenicity (pathotypeⅢ) respectively。2.According to the pathogenicity of Venturia inaequalis and the results of cluster analysis, 15 single spore isolates has been selected to study on their biological characters. For mycelial growth and sporulation number test of V. inaequalis to pH, temperature and light, the optiomal range of pH was 5.0~6.5, and temperature was 15~20℃. The lower light has significant effect on mycelial growth and sporulation number.3.Resistance of three apple cultivars tested to pathogens of apple scab was identified by means of inoculation with various pathogenicity of 3 isolates. The resistant level of cultivars to apple scab was Qinguan, Fuji and Gala, according to reactions of host and pathogen interaction.