Associations Among Triadimefon Sensitivity, Temperature Tolerance, Virulence And Genetic Diversity Of Population Of Blumeria Graminis F. Sp. Tritici In 2013

Wheat powdery mildew caused by Blumeria graminis f. sp. tritici(Bgt) is a worldwide wheat disease. In this study conducted in 2013, we detected and analyzed the correlation of the triadimefon resistance, temperature sensitivity, virulence, and genetic diversity of Bgt isolates from Yunnan, Sichuan, Beijing, Henan, Shaanxi and Gansu provinces.Triadimefon sensitivity of Bgt was tested by seed treatment and detached leaf segment methods. In the results, the EC50 for all 122 tested isolates ranged from 5.39 mg/L to 271.26 mg/L with an average of 84.05mg/L and its mean resistance factor(RF) of 40.22. The frequency of resistance reached up to 98.36%. Apart from Henan and Shaanxi province, 100% resistance frequency was collected among the isolates from the rest of province.The results also showed that there was a significant positive correlation between latent period and temperature ranging between 22℃~26℃ as well as a significantly negative correlation between disease severity and temperature. Temperature sensitivity of 90 Bgt isolates showed ET50 of 23.22℃ with the highest 25.15℃ and lowest 19.78℃. Distribution test on temperature sensitivity of Bgt isolates, as shown by SAS software analysis, was not normally distributed.Virulence of 290 Bgt isolates was tested using 31 differential cultivars/lines, and its diversity was calculated by PopGen software. The analysis showed variations in data collected from different provinces. The Nei index of virulence gene diversity in Yunnan province was the highest(Nei = 0.2359). The virulence gene diversity of isolates from Gansu was the lowest with the index 0.1879.Genetic diversity of 122 Bgt isolates assayed by using AFLP showed that the H index of genetic diversity ranged from 0.1915 to 0.2124, and the I index ranged from 0.2942 to 0.3200. The genetic diversity of isolates in Henan province was the lowest followed by the isolates in Beijing, while the highest genetic diversity for the isolates was recorded in Sichuan province. The genetic distance of the six provinces or cities ranged between 0.0140 and 0.0550 where as the genetic identity varied between 0.9465 and 0.9861.Correlation analysis among triadimefon resistance, temperature sensitivity, virulence, and genetic diversity of Bgt isolates indicated that there was no significant correlation between EC50 and virulence diversity or genetic diversity, while the value of EC50 and the number of virulence genes conformed to logarithmic equation. This suggested that there was a significant negative correlation between ET50 and virulence diversity, but no significant correlation between ET50 and genetic diversity. The results from this study show the influence of fungicides and temperature on pathogen virulence and genetic diversity, which then provide theoretical basis for disease control strategy.