Characterization and fungicide sensitivity of colletotrichum species causing strawberry anthracnose in eastern China

Abstract

Strawberry anthracnose caused by Colletotrichum spp. is one of the most serious diseases in the strawberry fields of China. In total, 196 isolates of Colletotrichum were obtained from leaves, stolons, and crowns of strawberry plants with anthracnose symptoms in eastern China and were characterized based on morphology, internal transcribed spacer (ITS), and b-tubulin (TUB2) gene sequences. All 196 isolates were identified as the Colletotrichum gloeosporioides species complex. In total, 62 strains were further identified at the species level by phylogenetic analyses of multilocus sequences of ITS, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), actin (ACT), Apn2-Mat1-2 intergenic spacer and partial mating type (ApMat), calmodulin (CAL), and TUB2. Three species from the C. gloeosporioides species complex were identified: Colletotrichum siamense, C. fructicola, and C. aenigma. Isolates of C. siamense were tolerant to high temperatures, with a significantly larger colony diameter than the other two species when grown above 36°C. The inoculation of strawberry plants confirmed the pathogenicity of all three species. C. siamense isolates resulted in the highest disease severity. The in vitro sensitivities of C. siamense and C. fructicola isolates to azoxystrobin and three demethylation-inhibitor (DMI) fungicides (difenoconazole, tebuconazole, and prochloraz) were determined. Both species were sensitive to DMI fungicides but not to azoxystrobin. C. siamense isolates were more sensitive to prochloraz, while C. fructicola isolates were more sensitive to difenoconazole and tebuconazole. The present study provides valuable information for the effective management of strawberry anthracnose.