Genetic Diversity Of Population Of Phytophthora Infestans From Qinghai

Late blight caused by the oomycete Phytophthora infestans (Mont.) de Bary occurred and had a rapidly epidemics in many potato countries all over the world. The occurrence and epidemics of this disease are dominated by the stucture and variation of P.infestans population, so the concerning researches on late blight has been focusing on the population stucture of the pathogen again in recent years. The present paper systematically revealed the genetic diversity of P.infestans on potato in Qinghai province, China, by analyzing the phenotypic stucture of local P.infestans population of the major potato production areas from 2006-2007 Qinghai province. The ralative results derived from the work are of significance to the breeding for resistance to late blight, and the management of the disease.Main results were summarized as follows:1. The 70 isolates of Phytophthora infestans were collected Qinghai Province from 2006 to 2007, four of them whose host were tomatoes, the others were potatoes.2. The isolates were inspected for mating type and monitoyed the oospores which were producted by self-fertility isolates. The results showed that 70 isolates tested were all subjected to A1 mating,no A2 mating type or relf-fertility isolate was found.3. 57 isolates out of all collected isolates were tested with 11 monogene R1～R11 potato clones of potato late blight differential host . Except Vir-9 or Vir-11, 9 of 11Virulence genes (Vir1, Vir2, Vir3, Vir4, Vir5, Vir6, Vir7, Vir8, Vir10) had been identified from these collections. The physiological race of P. infestans in Qinghai Province had become much complex. The results showed that there were 16 races in Qinghai Province and the dominant races were race 3.4.10 with frequency of 33.3%.4. All 70 isolates were tested to sensitivity to Metalaxyl, 64 isolates (91.43% )were sensitive, 2 isolates (2.85% )were intermediate resistance, and 4 isolates(5.71%)were highly resistance. The intermediate resistance isolates were distributed in Huangyuan county, All the highly resistance isolates collected from tomatoes were distribution of Xunhua county and the northland of Xining.The evidences from above results reflected that the phenotypic structure of P. infestans population in Qinghai shared complex diversity, but also showed some typiccharacteristics including that A1 mating type and complex races were the dominated components of phenotypic structure, most of them were sensitive to Metalaxyl.