| The aim of our study is to investigate the resistance of different cucumber varieties to Phytophthora melonis, and the changes of related defense enzyme activity by inoculated with about 5×103/mL suspension of P. melonis. Seven cucumber cultivars were selected for disease resistance screening, Changchunmici, Huaqingdadiaogua, Kangbing NO.2, Zaoqing NO.2, Zhongnong NO.20, Jinyou NO.1 and Yuexiu NO.3. The results showed that four middle resistant varieties were found, respectively Changchunmici, Huaqingdadiaogua, Kangbing NO.2 and Yuexiu NO.3, the other varieties showed susceptible to P. melonis, no immune and high resistant varieties were found. On uninoculated conditions, middle resistant variety Huaqingdadiaogua had higher activities of peroxidase （POD）, polyphenoloxidase（PPO）, phenylalnine ammonialyase（PAL）and β-1, 3-glucanase（GLU）than susceptible variety Zhongnong NO.20. After inoculation, only POD and PAL activities increased greatly in middle resistant variety, and other related defense enzyme activities kept stable. However, activities of POD, PPO, PAL and GLU all increased significantly in susceptible variety, and the increase degree was higher than that in middle resistant variety. In concluded, middle resistant variety mainly induced cell wall synthesis related enzyme, and thus prevented further invasion and spreading of the pathogen, however, related defense enzyme activities in susceptible variety increased greater. |
