Fernández-Ortuño Dolores, Chen Fengping, Schnabel Guido
School of Agricultural, Forestry & Life Sciences, Clemson University, Clemson, SC 29634.
Plant Dis. 2013 Jan;97(1):81-85. doi: 10.1094/PDIS-06-12-0539-RE.
Chemical control of gray mold of strawberry caused by Botrytis cinerea is essential to prevent pre- and postharvest fruit decay. For more than 10 years, the anilinopyrimidine (AP) cyprodinil and the phenylpyrrole fludioxonil (Switch 62.5WG) have been available to commercial strawberry producers in the United States for gray mold control. Both active ingredients are site-specific inhibitors and, thus, prone to resistance development. In this study, 217 single-spore isolates of B. cinerea from 11 commercial strawberry fields in North and South Carolina were examined for sensitivity to both fungicides. Isolates that were sensitive (53%), moderately resistant (30%), or resistant (17%) to cyprodinil were identified based on germ tube inhibition at discriminatory doses of cyprodinil at 1 and 25 mg/liter at 10 of the 11 locations. None of the isolates was fludioxonil resistant. Phenotypes that were moderately resistant or resistant to cyprodinil were not associated with fitness penalties for mycelial growth rate, spore production, or osmotic sensitivity. Detached fruit assays demonstrated cross resistance between the two AP fungicides cyprodinil and pyrimethanil, and that isolates that were characterized in vitro as moderately resistant or resistant were equivalent in pathogenicity on fruit sprayed with pyrimethanil (currently the only AP registered in strawberry as a solo formulation). This suggests that the in vitro distinction of moderately resistant and resistant isolates is of little if any field relevance. The absence of cross-resistance with fludioxonil, iprodione, cycloheximide, and tolnaftate indicated that multidrug resistance in the form of multidrug resistance phenotypes was unlikely to be involved in conferring resistance to APs in our isolates. Implications for resistance management and disease control are discussed.
化学防治由灰葡萄孢引起的草莓灰霉病对于预防采前和采后果实腐烂至关重要。十多年来，美国商业草莓种植者一直可使用苯胺嘧啶类药剂嘧菌环胺和苯基吡咯类药剂咯菌腈（62.5%咯菌腈·嘧菌环胺水分散粒剂）来防治灰霉病。这两种活性成分均为作用于特定位点的抑制剂，因此容易产生抗性。在本研究中，对来自北卡罗来纳州和南卡罗来纳州11个商业草莓田的217株灰葡萄孢单孢分离株进行了这两种杀菌剂的敏感性检测。基于在11个地点中的10个地点，在1毫克/升和25毫克/升的鉴别剂量嘧菌环胺下的芽管抑制情况，鉴定出对嘧菌环胺敏感（53%）、中度抗性（30%）或抗性（17%）的分离株。所有分离株均对咯菌腈不耐药。对嘧菌环胺中度抗性或抗性的表型与菌丝生长速率、孢子产生或渗透敏感性方面的适应性代价无关。离体果实试验表明，两种苯胺嘧啶类杀菌剂嘧菌环胺和嘧霉胺之间存在交叉抗性，并且在体外被鉴定为中度抗性或抗性的分离株在用嘧霉胺（目前在草莓中唯一登记的单剂苯胺嘧啶类药剂）处理的果实上致病性相当。这表明体外区分中度抗性和抗性分离株在田间几乎没有相关性。与咯菌腈、异菌脲、放线菌酮和噻菌灵不存在交叉抗性表明，我们的分离株中不太可能存在多药耐药表型形式的多药耐药性来赋予对苯胺嘧啶类药剂的抗性。文中讨论了抗性管理和病害防治的意义。
