Keinath Anthony P
Clemson University, Coastal Research and Education Center, Charleston, SC 29414-5329, USA.
Pest Manag Sci. 2009 Oct;65(10):1090-6. doi: 10.1002/ps.1797.
Isolates of Didymella bryoniae (Auersw.) Rehm, causal agent of gummy stem blight on cucurbits, developed insensitivity to azoxystrobin in the eastern United States 2 years after first commercial use in 1998. Baseline sensitivity of this fungus to azoxystrobin has never been reported. The objectives were to compare baseline sensitivities of D. bryoniae from South Carolina and other locations to sensitivities of isolates exposed to azoxystrobin for one or more seasons, and to compare sensitivity in vitro and in vivo.
Sixty-one isolates of D. bryoniae collected before 1998 were sensitive. Median EC50 was 0.055 mg L(-1) azoxystrobin (range 0.005 to 0.81). Forty isolates collected after exposure during 1998 also were sensitive. Fifty-three of 64 isolates collected in South and North Carolina between 2000 and 2006 were insensitive to 10 mg L(-1) azoxystrobin. Sensitive and insensitive isolates were distinguished by disease severity on Cucumis melo L. seedlings treated with azoxystrobin (20 or 200 mg L(-1)).
An azoxystrobin baseline sensitivity distribution was established in vitro for isolates of D. bryoniae never exposed to strobilurins. Baseline values were comparable with those of other ascomycetes. Insensitive isolates were found in fields with a history of strobilurin applications. An in vivo method distinguished sensitive and insensitive isolates.
葫芦科作物蔓枯病的病原菌——黄瓜壳二孢（Didymella bryoniae (Auersw.) Rehm），自1998年首次商业使用后两年，在美国东部对嘧菌酯产生了抗药性。此前从未报道过该真菌对嘧菌酯的基线敏感性。本研究的目的是比较来自南卡罗来纳州和其他地区的黄瓜壳二孢菌株的基线敏感性与接触过嘧菌酯一个或多个季节的菌株的敏感性，并比较体外和体内的敏感性。
1998年之前收集的61株黄瓜壳二孢菌株敏感。嘧菌酯的半数有效浓度（EC50）中位数为0.055 mg L(-1)（范围为0.005至0.81）。1998年接触过嘧菌酯后收集的40株菌株也敏感。2000年至2006年在南卡罗来纳州和北卡罗来纳州收集的64株菌株中，有53株对10 mg L(-1)嘧菌酯不敏感。通过用嘧菌酯（20或200 mg L(-1)）处理的甜瓜（Cucumis melo L.）幼苗上的病害严重程度来区分敏感和不敏感菌株。
建立了从未接触过甲氧基丙烯酸酯类杀菌剂的黄瓜壳二孢菌株的嘧菌酯体外基线敏感性分布。基线值与其他子囊菌的基线值相当。在有甲氧基丙烯酸酯类杀菌剂使用历史的田间发现了不敏感菌株。一种体内方法可以区分敏感和不敏感菌株。
