Research On The Phenotypic And Genetic Structure Of Phytophthora Infestans Population In Sichuan Province, China

Late blight caused by the oomycete Phytophthora infestans (Mont.) de Bary is a disastrous disease in the potato growing areas all over the world. Sichuan is one of the major potato production areas in China. The planting areas is 1,500km~2 in 2003s, It rises to 6,326ks~2 in 2006s . Along with the potato production's fast development, the potato transport becoming more frequently. The structure and variation of P.infestans population are change. It laid down a hidden danger for the occurrence and epidemics of this disease. It is necessary to production of potato to strengthen the research on population structure. This study focuses on the phenotypic(mating type,physiological race,biological traits,chemical resistance) and SSR genotypic diversity of. P.infestans population in the major potato producing areas in Sichuan province.Main results were summarized as follows:1. 158 isolates purified from the samples of potato late blight which collected from six major potato-growing areas in Sichuan province were tested for their mating types by using the reference isolates of A1 and A2 mating type. None oospore could be found .All of isolates was subjected to A1 mating type, no A2 mating type was found.2. Among 131 isolates tested with 4 potato clones of the international late blight differential hosts containing single dominant resistant gene R1,R2,R3,R4, 8 races could be distinguished with different virulence spectrum, and race 3,4 appeared at the highest frequency of 58%,followed by superior race of 3 with the frequency of 17.6% .3. The results from the chemical resistance test showed that among 60 isolates purified from the samples of potato late blight which collected from six major potato-growing areas in Sichuan province tested, none of them was found resistance to ridomil—M258WP,only found 8 isolates with intermediate resistance. So the ridomil—MZ58WP could continue use to control late blight in the areas.4. The results from the different illumination time test showed that the P.infestans couldn' t grow, the illumination had inhibitory effect to P.infestans growth. In different ph and nutrient conditions test the sporangium' s release rate. The results show the sμgar types and content had no affected to sporangium' s release rate. NaCL had inhibitory effect to it;PH4 was the optimum ph;PH 10 had suppression.5. Used 2 SSR-primer: Pi4B and Pi4G to detect 91 isolates from 7 different production areas in Sichuan. Found 8 SSR genotypes .which are D-05,D-03,F-01,F-03,F-06,G-02 and H-01. SSR genotype F-01 appeared at the highest frequency of 39.56%.