Research On The Genetic Differentiation Of Phytophthora Infestans From Tomato And Potato

Potato and tomato late blight is causing by Phytophthora infestans, and late blight is the most serious disease for the production of potato and tomato. This study focused on aggressive fitness, sensitivity to Metalaxyl and Azoxystrobin, mating type and SSR genotypic of 45 isolates of Phytophthora infestans (33 isolates from tomato and 12 isolates from potato). The results are as follow.1. Infection frequency, lesion size, sporulation capacity, and aggressive fitness of 12 isolates of Phytophthora infestans from potato and 9 isolates of Phytophthora infestans from tomato were tested using three potato and three tomato varieties. The result showed that isolates from potato and tomato had highier aggressive fitness in the original host. The aggressive fitness of isolates from potato in potato and tomato is 47832 and 1831, respectively. The aggressive fitness of isolates from tomato in tomato and potato is 53994 and 6300, respectively. The results indicated that potato late blight pathogen and tomato late blight pathogen posessed host specificity.(2)The sensitivity to Metalaxyl of 33 isolates of Phytophthora infestans was evaluated. Results suggested that 4 isolates were resistant to Metalaxyl, 29 isolates were hightly sensitive to Metalaxyl. The EC₅₀ value of sensitive isolaes were 0.0001μg/mL - 38.8997μg/mL. The results indicating most isolates of Phytophthora infestans from tomato were hightly sensitive to Metalaxyl.(3)The sensitivity to Azoxystrobin of 33 isolates of Phytophthora infestans was evaluated. The results suggested that all of the isolates were sensitive toAzoxystrobin. The highest and lowest EC50 value were 0.4538μg/mL and 0.0060μg/mL.(4)The mating type of 22 isolates of Phytophthora infestans from tomato, which collected from baoding, tangshan and Beijing, was evaluated. The result indicated that all the iaolates tested were A1 mating type.(5)33 isolates were detected and two SSR genotypes were recognized, which are B-03 and B-05, accounting for 93.9% and 6.1%, respectively.