Abstract：
Sterol demethylation inhibitor (DMI) fungicides continue to be essential components for the control of brown rot of peach caused by Monilinia fructicola in the United States and worldwide. In the southeastern United States, resistance to DMIs had been associated with overexpression of the cytochrome P450 14α-demethylase gene MfCYP51 as well as the genetic element Mona, a 65 bp in length nucleotide sequence located upstream of MfCYP51 in resistant isolates. About 20 years after the first survey, we reevaluated sensitivity of M. fructicola from South Carolina and Georgia to propiconazole and also evaluated isolates from Alabama for the first time. A total of 238 M. fructicola isolates were collected from various commercial and two experimental orchards, and sensitivity to propiconazole was determined based on a discriminatory dose of 0.3 μg/ml. Results indicated 16.2, 89.2, and 72.4% of isolates from Alabama, Georgia, and South Carolina, respectively, were resistant to propiconazole. The detection of resistance in Alabama is the first report for the state. All resistant isolates contained Mona, but it was absent from most sensitive isolates. It was unclear if the resistance frequency had increased in South Carolina and Georgia. However, the resistance levels (as assessed by the isolate frequency in discriminatory dose-based relative growth categories) did not change notably, and no evidence of other resistance genotypes was found. Analysis of the upstream MfCYP51 gene region in the resistant isolate CF010 revealed an insertion sequence described for the first time in this report. Our study suggests that current fungicide spray programs have been effective against increasing resistance levels in populations of M. fructicola and suppressing development of new resistant genotypes of the pathogen.
摘要：
在美国和世界范围内，甾醇去甲基化抑制剂（DMI）杀真菌剂仍然是控制由果莫尼氏菌引起的桃棕腐烂的必要成分。在美国东南部,对DMIs的抗性与细胞色素P45014α-脱甲基酶基因MfCYP51以及遗传元件Mona的过表达有关，在抗性分离株中位于MfCYP51上游的长度为65bp的核苷酸序列。第一次调查大约20年后，我们重新评估了来自南卡罗来纳州和乔治亚州的果粒分枝杆菌对丙环唑的敏感性，并首次评估了来自阿拉巴马州的分离株。从各种商业果园和两个实验果园共收集了238株果粒分离株，并根据0.3µg/ml的区分剂量确定了对丙环唑的敏感性。结果显示16.2%，89.2%和72.4%的分离株来自阿拉巴马州，格鲁吉亚,和南卡罗来纳州，分别,对丙环唑耐药。阿拉巴马州的耐药性检测是该州的第一份报告。所有耐药分离株都含有莫娜，但大多数敏感分离株都没有。目前尚不清楚南卡罗来纳州和乔治亚州的抵抗频率是否增加。然而,抗性水平（通过基于剂量的相对生长类别中的分离频率评估）没有显着变化，没有发现其他抗性基因型的证据。对抗性分离株CF010中上游MfCYP51基因区域的分析揭示了本报告中首次描述的插入序列。我们的研究表明，当前的杀真菌剂喷雾计划已有效地防止了果蝇种群中抗性水平的增加，并抑制了病原体的新抗性基因型的发展。
