Journal
PESTICIDE BIOCHEMISTRY AND PHYSIOLOGY
Volume 156, Issue -, Pages 123-128Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.pestbp.2019.02.011
Keywords
Fludioxonil; Dollar spot; Shos1 gene; Resistance risk; Fitness
Categories
Funding
- National Natural Science Foundation of China [31701810]
- Natural Science Foundation of Jiangsu Province [BK20160725]
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Sclerotinia homoeocarpa causes dollar spot disease on turfgrass and is a serious problem on many species worldwide. Fludioxonil, a phenylpyrrole fungicide, is not currently registered for dollar spot control in China. In this study, the baseline sensitivity to fludioxonil was established using an in vitro assay for 105 isolates of S. homoeocarpa collected from 10 locations in different regions of China. Results indicate that the frequency distribution of effective concentration for 50% inhibition of mycelial growth (EC50) values of the S. homoeocarpa isolates was unimodal (W = 0.9847, P = .2730). The mean EC50 value was 0.0020 +/- 0.0006 mu g/ml with a range from 0.0003 to 0.0035 mu g/ml. A total of 7 fludioxonil-resistant mutants were obtained in laboratory, the mutants were stable in fludioxonil sensitivity after the 10th transfer, with resistance factor (RF) ranging from 4.320 to > 13,901.4. The mutants showed a positive cross-resistance between fludioxonil and the dicarboximide fungicide iprodione, but not propiconazole, fluazinam, and thiophanate-methyl. When mycelial growth rate, pathogenicity and osmotic sensitivity were assessed, the mutants decreased in the fitness compared with their parental isolates. Sequence alignment of the histidine kinase gene Shos1 revealed a 13-bp fragment deletion only in one mutant, no mutations were observed on Shos1 in the rest resistant mutants.
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