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Identification and Prevalence of Botrytis spp. from Blackberry and Strawberry Fields of the Carolinas

Gray mold disease of blackberry and strawberry is caused by Botrytis cinerea and B. caroliniana in the southeastern United States. In this study, methods to distinguish both species were established and their prevalence was determined in commercial blackberry and strawberry fields. Using DNA from B. cinerea and B. caroliniana reference strains, a species-differentiating polymerase chain reaction (PCR) amplification was developed that amplified G3PDH gene fragments of two different sizes depending on the species. The PCR is performed with three primers (two species-differentiating forward primers and one universal reverse primer) and amplified a 238-bp product from B. cinerea and a 536-bp fragment from B. caroliniana reference isolates. A total of 400 Botrytis isolates were collected from 6 commercial blackberry and 11 strawberry fields of the Carolinas and identified to the species level by the new PCR method. Both Botrytis spp. were identified in blackberry and strawberry fields, but B. caroliniana was less common than B. cinerea. Only 33 of 202 isolates from blackberry fields were identified as B. caroliniana, and the majority of these isolates came from two fields in South Carolina. Only 1 of 198 isolates from strawberries was identified as B. caroliniana, and this isolate was found in central North Carolina. B. cinerea but not B. caroliniana isolates sporulated on potato dextrose agar and Kings medium B. Our results show that B. cinerea and B. caroliniana coexist in at least some commercial blackberry and strawberry fields of the Carolinas, with B. cinerea being the more prevalent species.