Phenotypic Characterization Of Phytophthora Infestans Population In Southwestern China

Potato late blight, caused by the aggressivepathogen Phytophthora infestans (Mont.) de Bary, is one of the most destructive potato diseases worldwide. A total of 688 isolates of P. infestans collected from five provinces in southwestern China during 2012 to 2018, were assessed with regard to mating type, response to metalaxyl, virulence race and mitochondrial (mt)DNA haplotype. In terms of mating type, 76% of 679 isolates were of the self-fertile mating type, 16.6% of the isolates were of the A1 mating type and only 7.8% were of the A2 mating type. Among the 299 isolates tested as representative samples, the frequency of resistant to metalaxyl reached 80% in these regions. The race structure of thestrains presented variety and complexity and 9.04 virulence factors per isolate and 92 virulence races were found among the 365 tested isolates. The most common pathotypes were 1.2.3.4.5.6.7.8.9.10.11 and 1.2.3.4.5.6.7.8.10.11, representing 46% of the tested strains. Three types of mtDNA haplotypes were found: 78.7% of 362 isolates were Ia, 16.6% were IIb and 4.7% were IIa. The results indicated that the population of P. infestans in southwestern China is diverse; andthe appearance of the self-fertile isolates with resistance to metalaxyl may contribute to the potential for sexual recombination and disease epidemics. (C) 2020 Friends Science Publishers