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Phylogenetic characterization of Colletotrichum gloeosporioides isolates from Florida strawberry and non-cultivated hosts

Michelle Oliveira: University of Florida

<div><em>Colletotrichum gloeosporioides</em> is the causal agent of Colletotrichum crown rot (CCR), a major disease affecting strawberries in the southern United States. Isolates from other non-cultivated hosts around strawberry fields have shown to serve as a source of inoculum for CCR. Recent multi-gene studies defined <em>C. gloeosporioides</em> as a complex species comprised of 22 species and one subspecies. The objective of our study was to phylogenetically characterize <em>C. gloeosporioides</em> isolates from strawberry and other non-cultivated plants around Florida strawberry fields. Five genomic regions: internal transcribed spacer (ITS), actin (ACT), calmodulin (CAL), chitin synthase (CHS-1), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were sequenced from 53 strawberry isolates and seven isolates from non-cultivated hosts (balsam apple, Brazilian pusley, smilax, magnolia, and wax myrtle). Phylogenetic analysis using a maximum likelihood method based on the Kimura 2 model and a discrete gamma distribution revealed that most of the isolates from Florida (77%) were closely related to <em>C. siamense</em>, whereas two of the strawberry isolates were closely related to <em>C. theobromicola (syn. C. fragariae)</em>. The biological importance of these different <em>Colletotrichum</em> species in the <em>C. gloeosporioides</em> species complex as well as fungicide resistance profiles are currently being investigated to determine whether different management strategies are needed in strawberry production fields in Florida.</div>