Characterization of Colletotrichum spp. sensitivity to carbendazim for isolates causing strawberry anthracnose in China.

Strawberry anthracnose caused by Colletotrichum species is an important disease that may cause significant economic losses. Based on multilocus sequence analyses and morphological characteristics, 64 isolates from strawberry anthracnose samples collected from nine Chinese provinces and municipalities were identified as three species: Colletotrichum fructicola (29 isolates), Colletotrichum siamense (23 isolates), and Colletotrichum nymphaeae (12 isolates). Isolates of C. siamense showed strong aggressiveness to fruit and leaves. Isolates of C. fructicola showed strong aggressiveness to crowns. Isolates of C. nymphaeae were weakly or not pathogenic to fruit, leaves, or crowns. Sensitivity to carbendazim was determined for a total of 75 isolates, including 11 previously preserved. Two isolates of C. siamense were highly resistant (HR) and 21 were moderately resistant (MR). Nine isolates of C. fructicola were sensitive (S), 24 were HR, and four were MR. All 15 isolates of C. nymphaeae were insensitive, and their mycelial growth was not completely inhibited on potato dextrose agar amended with 500 μg/ml carbendazim. Beta-tubulin (TUB2) of representative isolates was amplified and sequenced, revealing a glutamic acid substituted by alanine at codon 198 in HR isolates of C. siamense and C. fructicola. MR isolates of C. siamense and C. fructicola had a point mutation at codon 200, causing a replacement of phenylalanine acid by tyrosine. No point mutation was detected at codons 50, 167, 198, 200, or 240 in TUB2 of C. nymphaeae insensitive isolates. Overall, this study revealed that C. fructicola was the dominant species causing anthracnose on strawberry and could improve the understanding of the management of fungicide resistance in Colletotrichum species on strawberry in China.