Study On Virulence Differentiation Of Plasmopara Viticola In Xinjiang

Grapevine downy mildew, which caused by Plasmopara viticola,is one of the most damaging fungal disease of grapevine. However,so far the report about the population genetic structure of grape downy mildew isolates in Xin Jiang has not been found.We collected downy mildew samples from different grape species in different palnting areas in Xin Jiang and comprehensive method was used to detect the population genetic diversity, which consisted of identification of pathogenicity, morphological observation and measurement of sporangia and phylogenetic analysis.The aim of this research is to make a better understanding of genetic variation among population and explore the pathogenicity diversity and genetic structure.This will provide theoretical basis for grape breeding, disease forecasting and developing new disease control strategies. Main results are as follows: 1、 Use different method to preserve sporangia of P.viticola in different low temperaturesDifferent concentrations of method were used to preserve sporangia of P.viticola in different low temperatures.The results showed that the sporangia preserved in liquid nitrogen were more virulent than those in dimethylaulfoxide and glycerol at-72℃.Stored sporangia were used to inoculate susceptible Vitis resulting in infection on 21.2% of Leaf tissue after 360 days of storage as compared to 70.2% when inoculated with fresh sporangia. 2、Resistance Identification of Wine Grape Germplasm to Downy MildewThe 58 wine grape cultivars can be infected by downy mildew.The results showed that 58 varieties were divided into four categories including 16 varieties(27.59%) with higher resistance, 22 varieties(37.93%) with medium resistance, 14 varieties(24.14%) with susceptible resistance, 6 varieties(10.34%) with highest susceptible resistance via identification of resistance and cluster analyses. There was significant correlation between incubation period and disease index, the stronger the host resistance, the shorter incubation period. 3、Inoculation experimentsWe assessed the ability of the P. viticola isolates from different Vitis varieties to colonize eight isolate host leaf tissue. The results showed that the pathogenicity had obvious differences. This difference may caused by the host. In conclusion,there was genetic differentiation among isolates from different varieties.There is no significant between isolates from sporangial size and pathogenicity. 4、Genetic analysisDNA of P.viticola from 6 cities of Xin Jiang province were successfully extracted by CTAB method,SSR analysis showed that the relationship of strain were not close,and genetically complex.There was relationship between SSR analysis and their origin. Most of the strain from the same city were close and genetic similarity.