Genetic Diversity and Fungicide Sensitivity of <i>Botrytis cinerea</i> Isolates From Eucalypt Nurseries in Brazil

ABSTRACT This study aimed to assess the diversity, genetic structure and fungicide (thiophanate‐methyl and iprodione) sensitivity of Botrytis cinerea populations from Brazilian eucalypt nurseries. Among 106 isolates obtained from eight commercial nurseries in five Brazilian states, 77 haplotypes were identified. The frequency and distribution of transposons Boty and Flipper , the mating‐type alleles MAT1‐1 and MAT1‐2 , and inter‐simple sequence repeat (ISSR) marker analyses revealed different levels of genetic diversity and genetic structure among nurseries. Significant linkage disequilibrium in almost all subpopulations indicates a predominantly asexual reproductive mode in the eucalypt nurseries. However, the distribution of the mating‐type alleles MAT1‐1 and MAT1‐2 differed significantly from the expected 1:1 ratio for the total population, as well as for two of the nurseries evaluated, demonstrating a potential for recombination. Isolates resistant to at least one of the evaluated fungicides were detected in almost all nurseries. Of a total of 96 isolates screened for fungicide resistance, 1% were resistant only to thiophanate‐methyl, 7.3% were resistant only to iprodione and 41.6% were resistant to both fungicides. Analysis of molecular variance showed that genetic variation of B. cinerea populations was more related to nurseries than to states of origin. Both hierarchical cluster analysis and discriminant analysis of principal components identified four main genetic groups associated with fungicide‐resistant phenotypes. These findings provide evidence that B. cinerea populations from eight Brazilian eucalypt nurseries are highly diverse, structured and exhibit genetic and phenotypic singularities that should be considered when designing disease management strategies.