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Molecular characterization of Colletotrichum spp. isolates associated with southern highbush blueberry in north and central Florida

Maria Velez-Climent: Department of Plant Pathology, University of Florida

<div>Blueberry anthracnose is commonly known to be caused by <em>Colletotrichum gloeosporioides</em> and <em>C. acutatum</em>. Each of these has been shown to be a species complex. Defining the cryptic species within a complex is of particular importance because species may differ significantly in virulence, disease severity, host range and geographic distribution. Accordingly, the development of alternative disease management practices may be needed for each species. In this study, isolates of <em>Colletotrichum</em> spp. from symptomatic southern highbush blueberry fruit, stems and leaves were collected from 2013-2016 in north and central Florida. Colony and conidial characteristics grouped all isolates within the <em>C. gloeosporioides</em> species complex. Phylogenetic analyses of the internal transcriber spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), chitin synthase (CHS-1), manganese-superoxide dismutase (SOD2), and cytochrome b (CYTB) gene sequences confirmed the morphology-based taxonomic placement and further identified isolates as <em>C. siamense</em>. Isolates were also evaluated for sensitivity to QoI fungicides (10µg mL<sup>-1</sup> of azoxystrobin) and a fragment of the CYTB gene was sequenced. Fungicide resistant isolates were found in all plant parts tested and had a G143A mutation in CYTB. The presence of the QoI fungicide resistance mutation in the population indicates that azoxystrobin may no longer be a viable management option for blueberry anthracnose in north and central Florida.</div>