Poster: Biology & Disease Mgmt: Chemical Control
Profiling of Resistance to SDHI Fungicides in Botrytis cinerea from Strawberry Fields
M. HU (1), D. Fernández-Ortuño (2), G. SCHNABEL (1) (1) Clemson University, U.S.A.; (2) Universidad de Málaga, Spain
From 2012-13 to 2014-15, a total of 2,570 B. cinerea isolates were collected from strawberry fields in the eastern United States and their sensitivity to the SDHI fungicides including boscalid, fluopyram, fluxapyroxad, and penthiopyrad was assessed. Assays were based on visual assessment of presence or absence of mycelial growth on media amended with discriminatory doses of fungicides in microtiter plates. Overall frequencies of isolates resistant to boscalid, fluopyram, fluxapyroxad and penthiopyrad increased over the three years to 30.0, 1.0, 5.5, and 7.4%, respectively. Four resistance patterns designated A, B, C or D were found. Pattern A isolates were resistant to boscalid with the allele H272R at locus sdhB; Pattern B isolates were resistant to boscalid and penthiopyrad with the allele H272R or H272Y at locus sdhB; Pattern C isolates were resistant to boscalid, fluxapyroxad, and penthiopyrad with the allele H272Y at locus sdhB; and pattern D isolates were resistant to boscalid, fluopyram, fluxapyroxad, and penthiopyrad with alleles P225F or N230I at locus sdhB. Isolates with alleles H272R, H272Y, N230I or P225F were sensitive to a new SDHIs, benzovindiflupyr, with mean EC50 values less than 0.5 μg/ml for each genotype, suggesting that this fungicide may be useful for resistance management.