Santos, Ricardo F.
Fraaije, Bart A.
de Oliveira, Amanda A.
Total Authors: 5
 Univ Sao Paulo, Dept Plant Pathol & Nematol, Luiz de Queiroz Coll Agr, Piracicaba - Brazil
 Natl Inst Agr Bot, Cambridge - England
 Univ Sao Paulo, Dept Genet, Luiz de Queiroz Coll Agr, Piracicaba - Brazil
Total Affiliations: 3
FRONTIERS IN MICROBIOLOGY;
SEP 17 2020.
Web of Science Citations:
Downy mildew, caused byPlasmopara viticola, is the main disease affecting vineyards in subtropical Brazil. Here, we collected 94P. viticolaisolates from four organic and conventional vineyards in the two main grape-growing states of Brazil to evaluate the sensitivity to the quinone outside inhibitor (QoI) azoxystrobin by pheno- and genotyping assays. The impact of location, production system and sensitivity to QoI fungicides on the population genetics and structure ofP. viticolawas determined using 10 microsatellite markers. Cytochromebsequencing revealed that 28 and 100% of the isolates from vineyards under organic and conventional management carried the G143A mutation, respectively. The G143A mutation was associated with high levels of azoxystrobin resistance. Three out of the 94 isolates analyzed carried the M125I alteration, not previously described inP. viticola, which was associated with a five-fold reduction in azoxystrobin sensitivity compared to wild-type isolates. Haplotype network analysis based on cytochromebgene sequences suggested that the Brazilian populations are more closely related to the European than the North American population. A total of six haplotypes were identified, with two of them carrying the G143A mutation. Microsatellite analysis revealed high allelic and genotypic variation among the four populations. Population differentiation analyses indicated that state of origin directly influences the population biology ofP. viticola, while production system and QoI sensitivity have little effect. Great genetic diversity, sexual reproduction and high levels of admixture were observed in Rio Grande do Sul State. In contrast, populations in Sao Paulo State were dominated by a few clonal genotypes, and no admixed genotype was detected between the two genetic pools identified in the state. This study raises the hypothesis that winter weather conditions influence the overwinter survival strategy with profound effects in the population biology ofP. viticola. (AU)