Population Of The Phytophthora Infestans In Major Potato Growing Areas In 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 population diversity of P. infestans on potato in areas investigated in China, by analyzing the phenotypic (Mating type; physiological race; Metalaxyl sensitivity;) and genotypic (mt DNA hplotype) structure of the P. infestans population of the major potato production areas in china from 2006-2008. 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.Twenty isolates colleted from three provinces i.e. Sichuan, Yunnan and Inner Mongolia were tested with 11 potato clones of the international late blight differential hosts containing single dominant resistant gene R1, R2,R3, R4, R5, R6, R7, R8, R9, and R10 and R11. The result showed that the composition of the physiological races was complex in above three provinces. All tested resistant genes were compatible to the virulent genes of isolates of P. infestans assayed, and 85% of the tested isolates overcome the resistant genes R3. In the 20 isolates tested there were 19 different races. The racial distribution was no correlation with the regions where the isolates came from.2. The metalaxyl-resistant isolates of P. infestans were discovered in potato production areas in Inner Mongolia, Sichuan, Yunnan provinces. The frequencies of isolates with highly-resistant, intermediate resistant, and sensitive were 52%,24%,24%, respectively. Fouthermore, the research discovered the metalaxyl-resistance were completely different to isolates from different provinces. The 71 isolates collected from Inner Mongolia were resistant with the frequencies of 62%, the most isolates collected from Sichuan, were metalaxyl-sensitive and intermediate resistant with the frequencies of 40% respectively, the isolates collected from Yunnan were resistant with the frequencies of 50% and the sensitive isolates were 9%.3. The isolates from Inner Mongolia is all A1 mating type in the 124 isolates. Only 1 from 15 isolates of Yunnan province expresses as A2 mating type. The self-fertility isolates were discovered in Yunnan and Sichuan province, the frequency of self-fertility isolates in Sichuan province was 50%.4.124 representative isolates from the different districts were analyzed for mitochondrial DNA (mtDNA) haplotypes, and they were blongled toâ… a,â…¡a andâ…¡b respectively. The difference of distribution of mtDNA haplotype was remarkable in the regions. The frequencies ofâ… a,â…¡a andâ…¡b were 6%,66% and 28% of the 76 tested isolates from North China.32 isolates from Yunnan province were la with the frequency of 97%,â…¡b was found occurred with a low frequency(3%).â… a was discovered with a high frequency of 84% in 19 isolates from Sichuan province andâ…¡b type was 16%. So the predominate species of solates from northern areas wasâ…¡a and it was la from Yunnan and Sichuan province. Ib was no found in all region and all isolates belonged to the new population. The result showed the new population has displayed the old one in the major potato production areas in china.