Phytophthora variability based on metalaxyl resistance in Central Mexico

Tuesday, July 27, 2021
2:00 PM - 2:20 PM


Characterization of Phytophthora from the central highlands of Mexico contributes to the understanding of the amplitude of the geographical area in which variability occurs. The resistance of the pathogen to metalaxyl is considered a genetic character for variability studies. The objective of this work was to determine the phenotypic (in vitro resistance) and genotypic (polymorphisms of the gene that codes for the RPA 190 subunit of RNA polymerase I) variability of metalaxyl resistance of P. infestans and P. mirabilis collected in different localities of the Mexican central highlands. Phytophthora populations from Toluca showed a lower frequency of phenotypic variation and of resistant isolates than those from other localities. Metalaxyl in vitro resistant/sensitive inconsistencies determined by the amplitude of the EC50 values, did not allow any predictable behavior to be observed regarding the fungicide concentrations used, suggesting great genetic plasticity for this character. A single nucleotide polymorphism, SNP602GT, showed 62% association with resistant isolates. The absence of conformed groups regarding localities is supported by the wide genetic variability within each sampling site. However, on the basis of the phylogenetic analysis, the two species did conform different groups. It is concluded that Phytophthora variability detected in the localities near Toluca defines a greater geographical amplitude of the center of origin of this genus than previously accepted.

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