Genetic Diversity Of The Population Of Phytophthora Infestans On Potato Crop In Yunnan Province, China

Late blight caused by the oomycete Phytophthora infestans (Mont.) de Bary is a disastrous disease on potato worldwide. The occurrence and epidemics of this disease are mainly dominated by the structure and variation of P. infestans population. Since the reports about occurrence and epidemics of potato late blight rapidly increased from 1980s, the concerning researches on late blight has been focusing on the population structure of the pathogen again in recent years. The present paper systematically revealed the genetic diversity of P. infestans on potato in Yunnan province, China, by analyzing the phenotypic and genotypic structure of local P. infestans population of the major potato production areas from 2002～2005 in Yunnan province. The relative 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 total of 742 samples of potato late blight were collected from the main potato-growing areas in Yunnan province for monitoring the oospores. The results showed that none oospore could be found on these samples and reflected there might be no sexual reproduction or self-fertility isolates occurred in these potato-growing areas. 155 isolates purified from these samples were tested for their mating types by using the reference isolates of A1 and A2 mating type, and found that all of isolates was subjected to A1 mating type, no A2 mating type or self-fertility isolate was found.2. The results of virulence gene detection and monitoring trials with the standard late blight differentials each containing single R gene (R1-R11) demonstrated that all known R genes of potato could be overcome by corresponding virulence gene both in the artificial inoculation experiments and field monitoring trial of late blight differentials, the virulence component of race and its structure of P. infestans population in Yunnan was complicated as well. Among 152 isolates tested, 55 races could be distinguished with different virulence spectrum, and race 1.2.3.4.5.6.7.8.9.10 appeared at the highest frequency of 32.89%, followed by superior race of 1.2.3.4.5.6.7.8.9.10.11 with the frequency of 18.18%.3. The results from the metalaxyl-sensitivity test showed that, among 153 isolates tested, the frequency of isolates with resistance, intermediate resistance, and sensitive to metalaxyl...