Abstract:Blumeria graminis f. sp. tritici (Bgt), which caused wheat powdery mildew disease, survive in very short period away from the host wheat. In order to determine the survival time of conidia of Bgtin vitro, conidia germination and disease severity of wheat leaves infected by Bgt conidia were studied after treatments with serial temperatures and time. The results showed that conidia germination rates and disease severities were decreased as temperatures increased. There was no conidia germination and wheat infection when the conidia were kept at 30℃ for 1 d. After keeping at 25℃-28℃ for 1 d, the conidia germination rate was 11.1%-21.8%, and disease severity was 10.6%-15.5%. At 14℃-22℃ for 1 d, the conidia germination rate was 27.4%-29.1%, and severity was 35.5%-69.1%, while no conidia germination and wheat infection for 4 d. As well as, the conidia were kept at 4℃-8℃ for 1 d with 36.6%-43.2% germination rate and 82.5%-91.0% severity, while the germination rate was 5.0%-6.7%, and severity was 7.8%-16.0% after kept for 8 days. All these data indicated that there was a significantly negative correlation between survival time of conidia of Bgtin vitro and temperature, the lifetime of conidia decreased along with temperature increased, such as 8 d at 4℃-8℃, 3 d at 18℃-22℃, 1 d at 25℃-28℃, and less than 1 d at 30℃. Based on these results, a model of relationship between survival time of conidia of Bgtin vitro and temperature was constructed. These could provide the basis for modeling dispersal distance of wheat powdery mildew.