Fernández-Ortuño Dolores, Chen Fengping, Schnabel Guido
School of Agricultural, Forestry, and Life Sciences, Clemson University, Clemson SC 29634.
Plant Dis. 2012 Aug;96(8):1198-1203. doi: 10.1094/PDIS-12-11-1049-RE.
Botrytis cinerea, the causal agent of gray mold disease, is one of the most important plant-pathogenic fungi affecting strawberry. During the last decade, control of gray mold disease in the southeastern United States has largely been dependent on captan and the use of at-risk fungicides with single-site modes of action, including a combination of the quinone outside inhibitor (QoI) fungicide pyraclostrobin and succinate dehydrogenase inhibitor (SDHI) fungicide boscalid formulated as Pristine 38WG. Reports about loss of efficacy of Pristine in experimental fields in North Carolina prompted us to collect and examine 216 single-spore isolates from 10 conventional fields and 1 organic field in North Carolina and South Carolina in early summer 2011. Sensitivity to pyraclostrobin or boscalid was determined using a conidial germination assay with previously published discriminatory doses. Pyraclostrobin- and pyraclostrobin+boscalid-resistant isolates were found in all conventional fields (with some populations revealing no sensitive isolates) and in the organic field. Among the isolates collected, 66.7% were resistant to pyraclostrobin and 61.5% were resistant to both pyraclostrobin and boscalid. No isolates were identified that were resistant to boscalid but sensitive to pyraclostrobin, indicating that dual resistance may have derived from a QoI-resistant population. The molecular basis of QoI and SDHI fungicide resistance was determined in a subset of isolates. Polymerase chain reaction-restriction fragment length polymorphism analysis of the partial cytochrome b (CYTB) gene showed that pyraclostrobin-resistant isolates possessed the G143A mutation known to confer high levels of QoI fungicide resistance in fungi. Boscalid-resistant isolates revealed point mutations at codon 272 leading to the substitution of histidine to arginine (H272R) or tyrosine (H272Y), affecting the third Fe-S cluster region of the iron-sulfur protein (SdhB) target of SDHIs. The results of the study show that resistance to QoI fungicides and dual resistance to QoI and SDHI fungicides is common in B. cinerea from strawberry fields in the Carolinas. Resistant strains were more frequent in locations heavily sprayed with QoI and SDHI fungicides. However, resistance to both fungicides was also found in the unsprayed, organic field, indicating that some resistant strains may have been introduced from the nursery.
灰葡萄孢是灰霉病的病原菌，是影响草莓的最重要的植物病原真菌之一。在过去十年中，美国东南部灰霉病的防治很大程度上依赖于克菌丹以及使用具有单作用位点的高风险杀菌剂，包括醌外抑制剂（QoI）类杀菌剂吡唑醚菌酯和琥珀酸脱氢酶抑制剂（SDHI）类杀菌剂啶酰菌胺复配而成的“施得益38WG”。北卡罗来纳州试验田关于“施得益”药效丧失的报道促使我们在2011年夏初从北卡罗来纳州和南卡罗来纳州的10个常规种植田和1个有机种植田中收集并检测了216个单孢分离株。使用先前公布的鉴别剂量通过分生孢子萌发试验来测定对吡唑醚菌酯或啶酰菌胺的敏感性。在所有常规种植田（一些群体中未发现敏感分离株）和有机种植田中均发现了对吡唑醚菌酯以及对吡唑醚菌酯和啶酰菌胺双重耐药的分离株。在所收集的分离株中，66.7%对吡唑醚菌酯耐药，61.5%对吡唑醚菌酯和啶酰菌胺均耐药。未鉴定出对啶酰菌胺耐药但对吡唑醚菌酯敏感的分离株，这表明双重耐药可能源自对QoI耐药的群体。在一部分分离株中确定了对QoI和SDHI类杀菌剂耐药的分子基础。对部分细胞色素b（CYTB）基因进行聚合酶链反应-限制性片段长度多态性分析表明，对吡唑醚菌酯耐药的分离株具有已知能使真菌对QoI类杀菌剂产生高水平耐药性的G143A突变。对啶酰菌胺耐药的分离株在第272位密码子处出现点突变，导致组氨酸被精氨酸（H272R）或酪氨酸（H272Y）取代，影响了SDHIs作用靶标铁硫蛋白（SdhB）的第三个铁硫簇区域。研究结果表明，对QoI类杀菌剂的耐药性以及对QoI和SDHI类杀菌剂的双重耐药性在卡罗来纳州草莓田的灰葡萄孢中很常见。在大量喷施QoI和SDHI类杀菌剂的地方，耐药菌株更为常见。然而，在未喷施药剂的有机种植田中也发现了对这两种杀菌剂均耐药的情况，这表明一些耐药菌株可能是从苗圃引入的。
