Colcol Jeneylyne F, Baudoin Anton B
Monsanto Company, Huxley, IA 50124.
Department of Plant Pathology, Physiology and Weed Science, Virginia Tech, Blacksburg 24061.
Plant Dis. 2016 Feb;100(2):337-344. doi: 10.1094/PDIS-01-15-0012-RE. Epub 2015 Dec 4.
The sensitivity of downy mildew (DM, Plasmopara viticola) and powdery mildew (PM, Erysiphe necator) of grape (Vitis sp.) to commonly used nondemethylation inhibitor, single-site fungicides in and near Virginia was determined from 2005 to 2007, with more limited additional sampling in subsequent years. In grape leaf disc bioassays, 92% of the P. viticola isolates were quinone outside inhibitor (QoI, azoxystrobin) resistant but none were resistant to mefenoxam. In all, 82% of the E. necator isolates were QoI resistant. Most of the QoI-resistant P. viticola and E. necator isolates contained >95% of the G143A point mutation, which confers high levels of QoI resistance. In contrast, QoI-sensitive P. viticola isolates contained less than 1% of G143A. In total, 1 of 145 and 14 of 154 QoI-resistant P. viticola and E. necator isolates (able to grow on azoxystrobin concentration ≥1 μg/ml), respectively, contained <1% G143A. In total, 61 E. necator isolates from 23 locations were tested against thiophanate methyl, and the majority grew well on leaf tissue treated with 50 and 250 μg/ml. Through 2012, none of the E. necator isolates were resistant to boscalid and quinoxyfen. However, in 2013, quinoxyfen-resistant E. necator was detected in one vineyard experiencing difficulties with powdery mildew control. No 50% effective concentration value could be calculated but these isolates tolerated labeled rates with only limited inhibition. QoI (E. necator and P. viticola) and benzimidazole (E. necator) resistance were widespread in Virginia, rendering these materials inadvisable for control of these diseases. The practical importance and current distribution of quinoxyfen resistance needs further investigation.
2005年至2007年期间，对弗吉尼亚州及其周边地区葡萄（葡萄属）霜霉病（DM，葡萄生单轴霉）和白粉病（PM，葡萄钩丝壳）对常用的非去甲基化抑制剂、单作用位点杀菌剂的敏感性进行了测定，后续年份的采样范围更有限。在葡萄叶片圆盘生物测定中，92%的葡萄生单轴霉分离株对醌外抑制剂（QoI，嘧菌酯）具有抗性，但无一株对甲霜灵具有抗性。总体而言，82%的葡萄钩丝壳分离株对QoI具有抗性。大多数对QoI具有抗性的葡萄生单轴霉和葡萄钩丝壳分离株含有>95%的G143A点突变，该突变赋予了高水平的QoI抗性。相比之下，对QoI敏感的葡萄生单轴霉分离株中G143A的含量不到1%。在总共145株对QoI具有抗性的葡萄生单轴霉分离株和154株对QoI具有抗性的葡萄钩丝壳分离株（能够在嘧菌酯浓度≥1μg/ml的条件下生长）中，分别有1株和14株的G143A含量<1%。总共对来自23个地点的61株葡萄钩丝壳分离株进行了甲基硫菌灵测试，大多数分离株在经50和250μg/ml处理的叶片组织上生长良好。截至2012年，没有一株葡萄钩丝壳分离株对啶酰菌胺和喹氧灵具有抗性。然而，在2013年，在一个白粉病防治困难的葡萄园检测到了对喹氧灵具有抗性的葡萄钩丝壳。无法计算出50%有效浓度值，但这些分离株仅在有限抑制的情况下耐受标记剂量。QoI（葡萄钩丝壳和葡萄生单轴霉）和苯并咪唑（葡萄钩丝壳）抗性在弗吉尼亚州广泛存在，因此不建议使用这些药剂来防治这些病害。喹氧灵抗性的实际重要性和当前分布情况需要进一步研究。
