Identification of strobilurin and benzimidazole resistance in Colletotrichum cereale isolates causing anthracnose on creeping bentgrass putting greens in Mississippi and Alabama
Young, Joseph Ronald
Anthracnose, incited by Colletotrichum cereale, is a destructive disease of physiologically stressed creeping bentgrass putting greens in Mississippi and Alabama. Anthracnose severity and frequency of occurrence have increased over the past 15 years, and fungicide resistance may have had a role in the increase. In vitro bioassays were performed to evaluate thiophanate methyl and azoxystrobin against C. cereale isolates exposed to the fungicides and baseline isolates that had not been exposed to either fungicide. All isolates collected from creeping bentgrass were uninhibited by both fungicides at discriminatory doses. Partial nucleotide sequences of the â-tubulin 2 (thiophanate methyl) or cytochrome b (azoxystrobin) gene was compared to confirm fungicide resistance. Thiophanate methyl resistance was conferred by either a point mutation from glutamic acid to alanine at position 198, or phenylalanine to tyrosine at position 200. Azoxystrobin resistance was conferred by an amino acid point mutation from glycine to alanine at position 143.