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Exploring mechanisms of resistance to dimethachlone in Sclerotinia sclerotiorum
Author(s) -
Firoz Md. Jahangir,
Xiao Xiang,
Zhu FuXing,
Fu YanPing,
Jiang DaoHong,
Schnabel Guido,
Luo ChaoXi
Publication year - 2016
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.4051
Subject(s) - sclerotinia sclerotiorum , sclerotinia , biology , mycelium , procymidone , mutant , iprodione , fungicide , microbiology and biotechnology , horticulture , osmotic pressure , botany , gene , genetics
BACKGROUND The dicarboximide fungicide dimethachlone has been widely used in China for more than 12 years to control the Sclerotinia stem rot caused by Sclerotinia sclerotiorum disease. First signs of resistance in the field are reported at low frequency. In this study, four resistant isolate/mutants were used to explore still unknown mechanisms leading to dimethachlone resistance. RESULTS The resistant isolate/mutants had significantly higher EC 50 values compared with the sensitive control isolates. Cross‐resistance was confirmed between dimethachlone and procymidone, iprodione and fludioxonil. The resistant isolate/mutants revealed a decreased mycelial growth rate, were less pathogenic on leaves of oilseed rape, were more sensitive to osmotic pressure and oxidative stress and released more electrolytes compared with the sensitive isolates. Only in one lab mutant did we find a point mutation ( V238A ) in the SsOs1 gene of the high‐osmolarity glycerol ( HOG ) signalling pathway. The expression of this gene was lost in the field resistant isolate HN456 ‐1‐ JBJ and decreased in mycelium that was subjected to either high osmotic pressure or dimethachlone; however, another key gene in the HOG pathway, SsHog1 , could be induced in the resistant isolate and mutants with NaCl treatment. CONCLUSION This study demonstrates that resistance to dicarboximide fungicide dimethachlone in S. sclerotiorum is emerging in China. Several fitness parameters, including mycelial growth rate, sclerotia formed in vitro , aggressiveness on leaves and osmotic and H 2 O 2 sensitivity, indicate that the resistant strains may not effectively compete with sensitive isolates in the field in the absence of selection pressure. Lost expression or the V238A point mutation in the SsOs1 gene may confer resistance to dicarboximide fungicide dimethachlone in S. sclerotiorum , but this study illustrates that other, yet unknown mechanisms also exist. © 2015 Society of Chemical Industry