The Resistance And Mechanisms Of Pumpkin Varietis Against Pumpkin Powdery Mildew

Powdery mildew of pumpkin is a widespread disease worldwide, the long-standing problem of pumpkin production, to produce a certain result in economic losses as a pumpkin production of a limiting factor. The disease causing Pumpkin powdery mildew was observed and identified in WuWei districts of Gansu .The chief pathogens, according to microscopy, spore germination experiment and identification of the host response to infection, were identified as Sphaerotheca fuligine. And the determination of host range for the melon, cucumber, balsam pear, snake gourd, winter melon, pumpkin 10 categories for vaccination. The results showed that the region arising from Wuwei, Gansu Province pumpkin powdery mildew pathogen of melon, cucumber, bitter gourd, wax gourd, pumpkin and other 9 kinds of Cucurbitaceae force are infected, but non-infected sponge gourd force.Resistance of ten Pumpkin cultivars to powdery mildew was studied by means of natural infection in the field and artificial inoculation in the laboratory. The results showed that the resistance to powdery mildew among the Pumpkin cultivars was significant different. Xanxing, Hongli and Tianli were resistant; Guangban,Tianran and Hongfu were susceptible. Moreover, the level of resistance to the disease between field natural elaluation and laboratory artificial inoculation was significant positive correlation.The result indicated that the primary pathogen was ascus subphylum ,Sphaerotheca fuligine,the inoculation concentration was 2.5×105 to 5.0×l05 spores/mL,laying within 0.5h and the treatment of two euphylla, , the temperature for 25 to 30℃, the humidity in 80 to 90﹪is easiest to be taken bad of pumpkin.The result showed that the resistance was negative correlated to stomatal number and the germination rate of conidia. Statistical analysis indicated that the stomatal density were not correlated with the resistance to powdery mildew in six pumpkin cultivars. The variation of some biochemical index of pumpkin cultivars such as the content of chlorophyll, the activity of peroxidase (POD) and activity of phenylalnine ammonia-lysae were analyzed by testing pumpkin seedling whose leaves have been inoculated and uninoculated. The result showed that the resistance was positively correlated to the content of chlorophyll. And responses of peroxidase (POD) and phenylalnine ammonia-lysae (PAL) of pumpkin seedling leaves were analyzed after inoculation with Sphaerotheca fuligine. The results showed that the activities of POD and PAL of non-inoculated (CK) were similar among cultivars; The activities of POD and PAL in the susceptible cultivars increased more than that of resistant after inoculation with Sphaerotheca fuligine , and the changes were negatively correlated with the pumpkin resistance against powdery mildew , while the increasing rate of the activities of PAL in the susceptible was less than that of resistance after inoculation , and the changes were positively correlated with the resistance. And the activity of POD emerged two higher points after inoculation of resistant,but only one of susceptible.It was concluded that the changes of POD and PAL activities in the inoculated leaves were closely correlated with the pumpkin resistance against powdery mildew.