The Detection Of SSR Genotypes And Sensitivity To Azoxystrobin And Ridomil Gold Of Phytophthora Infestans

Potato late blight,caused by the oomycete pathogen Phytophthora infestans,is the most devastating disease in potato production in the world.With the two microsatellites Pi4B and Pi4G,the SSR genotypes of Phytophthora infestans collected from Weichang Hebei,Congli,Hebei,and Keshan,Heilongjiang in 2006 and 2007 were identified.The mating type and the sensitivities to azoxystrobin and ridomil gold of Phytophthora infestans were also determined.The results were as follows.1.With the two microsatellites Pi4B and Pi4G,a total of Five SSR genotypes of Phytophthora infestans,which were F-01,F-02,F-05,F-06 and G-03,were identified among the 171 isolates collected in China from 2006 to 2007.SSR genotype G-03 was a new genotype.2.Three SSR genotypes were found in 107 strains from Weichang and Chongli of Hebei,which were F-01,F-05 and F-06.101 out of 107 strains prosessed genotype F-01, accounting for 94.4%.Genotype F-01 dominated the population of P.infestans population tested.Five SSR genotypes were identified in 64 strains from Keshan of Heilongjiang, which were F-01,F-02,F-05,F-06 and G-03.35 and 23 out of 64 strains,accounting for 54.7%and 35.9%,posessed genotype F-01 and F-06,respectively.Genotype F-01 and F-06 dominated the P.infestans population from Keshan,Heilongjiang.3.The mating type of a total 207 strains of Phytophthora infestans,which sampled from Weichang and Chongli of Hebei,and Keshan of Heilongjiang in 2006 and 2007,were assayed.The results showed that all the strains tested were A1 mating type,and no A2 mating type were found.4.The sensitivities to azoxystrobin of 207 strains of Phytophthora infestans,which sampled from Weichang and Chongli of Hebei,and Keshan of Heilongjiang in 2006 and 2007,were assayed.The results showed that all strains tested were sensitive to azoxystrobin.The mean effective concentration(EC₅₀)values of strains from Weichang and Keshan were 0.0745±0.0033μg/mL and 0.0766±0.0041μg/mLμg/mL,respectively. The mean EC₅₀values of strains from Weichang and Chongli were 0.0612±0.0049μg/mL and 0.0628±0.0039μg/mL.The mean EC₅₀values was 0.0715±0.0023μg/mL,which can be used as the base line-sensitivity of P.infestans to azoxystrobin.5.The sensitivities to ridomil gold of P.infestans,30 strains from Weichang,30 strains from Keshan,22 strains from Weichang and 8 strains from Chongli,were determined,respectively.Among the tatal 90 strains,the frequency of sensitive, intermediate and resistant strain were 58.9%,32.2%and 8.9%,respectively.EC₅₀values of the most sensitive strain was 0.0063μg/mL,and EC₅₀values of the most insensitive strain was 169.7991μg/mL,the most insensitive was 26952 folds of the most sensitive.