Over-summmering And Monitor Of Epidemic Dynamic Of Wheat Powdery Mildew (Blumeria Graminis F.sp.tritici) In Sichuan Province

Wheat powdery mildew which is an important product atmospheric disease is caused by Blumeria graminis f. sp. tritici. B. graminis f. sp. tritici is a powerful, specific obligate parasite. Therefore, the over-summering of the pathogen and the summer host are the key factors which affect powdery mildew incidence and prevalence. In order to clarify the primary infection source and its over-summering areas of wheat seedlings in Sichuan Province, the over-summering of cleistothecium and conidia from volunteer wheat seedlings, also the survival condition of its summer host (wheat) in Sichuan Province were studied. And the living conditions of the pathogen and its host in the summer in Sichuan Province were clarified. In order to further clarify the epidemic regularity of wheat powdery mildew in Sichuan Province, we had a systematic survey of the wheat powdery mildew occurrence of Chuanyu20 and Chuannong26 in 2008 and 2009. According to powdery mildew disease index, average severity, prevalence rate of the variation over time, the occurrence and epidemic dynamics of wheat powdery mildew in Yaan were analyzed.The result showed that the pathogen of wheat powdery mildew over-summered at an altitude of 600 meters sea level (include 600 meters) in Sichuan Province and then to infect the wheat in autumn. In the investigation on the volunteer wheat seedlings in Sichuan Province, there were a lot of summery wheats in many areas and some of the wheat occurred powdery mildew. Systematic observation of the wheat in the farm of Sichuan Agriculture University in Yaan was made and what was observed was that the summery wheat existing in great quantity and the morbidity rate was really high, what can even be found was that high-shady crops were more easily affected by powdery mildew than shorter ones, some of them could become carriers to survive until fall seeding stage which providing popular of wheat powdery mildew. The survival and spore of the cleistothecium researching by microscopy showed that the cleistothecium store indoors, under the eaves, and the dryer can survive through the summer. At the same time, the storage cleistothecium could through the summer and successful infect wheat to powdery mildew were confirmed through isolation experiments. The temporal dynamics of wheat powdery mildew in 2008 and 2009 showed that the general rate, disease index, the severity of the approximate time curve of wheat powdery mildew were tested "S" curve. Using SPSS software conducted logistic curve and S-curve fitting of the general rate, the average severity and the disease index of wheat powdery mildew which Chuannong26 occurred in 2009, the results showed that the logistic curve fit to the average severity was the best fitting, R2=0.924, and the logistic curve fit to the disease index was the best fitting for Chuanyu20, R2=0.968. The disease of wheat powdery mildew in 2008 and 2009 showed that the beginning to see the diseased plant in 2009 is earlier than 2008. The severity of disease in Chuannong26 was significantly higher than Chuanyu20 were studied from the overall trend in these two years. The results of two years were comparatived, it showed that there were significant differences in the dynamic of wheat powdery mildew epidemic each year. Although the wheat powdery mildew disease had the highest general rate of 100% each year, but the disease index and the average severity were significantly different. As can be seen from the apparent infection rate, although the dynamic changes of apparent infection rate were different at the same time each year, but the experiment in these two years had the same result can be drawn is that the apparent infection rate and the disease index showed a positive correlation between growth.