| Potato late blight, caused by the Phytophthora infestans, is one of the most devastating diseases in potato production. It is necessary to study population structure of P. infestans for controlling the late blight. The mtDNA haplotypes of 286 isolates of P. infestans collected from 1996 to 2007 in seven Provinces (cities) in China, were assessed using PCR-RFLP and the distribution of mtDNA haplotypes was analyzed in order to better understand the P. infestans in the molecular level. In addition, the sensitivity to the three fungicides (azoxystrobin, Metalaxyl-M mancozeb and metalaxyl) of P.infestans collected from some areas of two Provinces of Hebei and Jilin in 2008.The main results are as follows:1. Eight foreign isolates, which was known to their mtDNA haplotypes, were used as reference ones and the mitochondrial halpotypes of the Chinese 286 strains of P. infestas were determined using PCR-RFLP method. The three mtDNA haplotypes, i.e. Ia,IIa and IIb, were found among the tested isolates. Of 286 isolates, the mtDNA haplotype of 266 ones (165 in Hebei province, 97 from Heilongjiang province,1 isolate from Inner Mongolia Autonomous Region, 2 isolates form Yunnan province and 1 from Chongqing city; )was IIa, which was the most widely distributed in five provines (city). The haplotype of 14 isolates (12 from Fujian province, 1 from Hebei province and 1 from Sichuan province) was IIb and the one 6 isolates from Yunnan province was Ia.2. The mating type of 97 isolates collected from Weichang county in Hebei province and Changchun city in Jilin province in 2008 were determined and the results indicates all tested isolates were the A1 mating type.3. The sensitivities to azoxystrobin of 97 isolates collected from Weichang county in Hebei province and Changchun city in Jilin province in 2008 were assayed and the results showed that all tested isolates were sensitive. The mean values of median effective concentration (EC50) among the isolates collected from the two regions were 0.0747μg/mL and 0.0508μg/mL, respectively. The mean EC50 value of isolates from the two areas was 0.0668μg/mL, which can be used as the base line-sensitivity of P. infestans to azoxystrobin. 4. The sensitivities to Metalaxyl-M mancozeb of 65 isolates from Weichang country of Hebei province and 35 strains from Changchun city of Jilin province were investigated. The results indicated that the majority was resistant and the percentages of highly-resistant, intermediate-resistant and sensitive were separately 72.3%, 26.2% and 1.5%. Of however, majority was Metalaxyl-M mancozeb-sensitive and the percentages of sensitive, intermediate-resistant, and resistant strains were 81.3%, 15.6 % and 3.1%, respectively. Of the 35 isolates sampled from Weichang county of Hebei province, all isolates were resistant to metalaxyl and the percentage of highly-resistant ones was 91.7%. Of 18 isolates sampled from Changchun city, major isolates were sensitive to metalaxyl and the percentages of sensitive, intermediate–resistant and highly- resistant ones were separately 77.8%, 16.7% and 5.5%. It was also detected that Metalaxyl-M mancozeb and metalaxyl could make mycelia of resistant isolates grow well in the rye medium.
|
PDF Full Text Request