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Multilocus sequence analysis reveals Colletotrichum nymphaeae as the dominant species causing strawberry anthracnose in the United States

Nan-Yi Wang: University of Florida

<div>Strawberry anthracnose, caused by <em>Colletotrichum acutatum</em>, is one of the primary limiting factors in fruit production fields in the United States. Recent research focusing on the phenotypic and genetic diversity of this species has shed light on the complexity of <em>C. acutatum</em> species. In this study, we performed multilocus sequence analysis of four housekeeping genes to characterize 218 anthracnose-associated <em>C. acutatum</em> isolates collected over a 23-yr period from the symptomatic roots, crowns, or fruit of strawberry from Florida, North Carolina, Virginia, and California, including those that have been confirmed to be resistant to quinone-outside inhibitor (QoI) fungicides. The results revealed a dominant species, <em>C. nymphaeae</em>, accounting for 97.7% of the isolate collection (212/217), whereas the other identified species, <em>C. fioriniae</em>, comprised 2.3% of the population (5/217). All QoI-resistant isolates were found in the <em>C. nymphaeae </em>clade. A subset of 12 isolates representing <em>C. nymphaeae</em> populations sensitive or resistant to QoI fungicides from root or fruit tissue of strawberry was then selected for comparison of pathogenicity on strawberry. Of these isolates tested, all exhibited a similar degree of aggressiveness and caused indistinguishable symptoms on strawberry crowns and fruit. Overall, our results indicate genetic and pathogenic homogeneity in the <em>C. acutatum</em> populations associated with strawberry production in the United States.</div>