The North Georgia Mountains are the southernmost region along the United States East Coast where European wine grapes (Vitis vinifera) are grown commercially. Epidemics of downy mildew, caused by Plasmopara viticola, are frequent and severe, but little is known about the epidemiology and population biology of the pathogen in this region. Disease monitoring in an experimental vineyard from 2015 to 2017 indicated that times of disease onset and progress rates were highly variable across years and cultivars. Oospores were observed microscopically, and simulation with a process‐based model indicated presence of conditions favourable for oospore germination in the spring and early summer each year. A total of 409 P. viticola isolates collected over three years were genotyped with seven microsatellite markers, revealing very high genotypic diversity, which when combined with the observation of oospores is indicative of a sexually reproducing population. Among the 409 isolates, 225 multilocus genotypes (MLGs) were identified, of which 164 were detected only once and 61 were repeated (clonal). Eight MLGs (represented by 28 isolates) were detected across years, suggesting the possibility of asexual overwintering of P. viticola in this region. Across sampling dates, the percentage of isolates belonging to nonrepeated (unique) MLGs ranged from 27.3% to 63.2%. Even towards the end of the annual epidemic, the percentage of isolates in nonrepeated MLGs was still relatively high, around 30%. These MLGs may have originated from oospores germinating late during the growing season, although incomplete sampling at earlier dates and contribution by immigration cannot be fully excluded.

中文翻译：

---

在美国北佐治亚山脉的一个孤立葡萄园中，葡萄霜霉病（Plasmopara viticola）有性繁殖和无性繁殖的时间疾病动态和相对重要性

佐治亚州北部山脉是美国东海岸最南端的地区，欧洲酿酒葡萄（Vitis vinifera）商业化种植。由葡萄小单胞菌引起的霜霉病流行很严重，但对该地区病原体的流行病学和种群生物学知之甚少。从2015年到2017年，在一个实验性葡萄园中进行的疾病监测表明，疾病的发作时间和进展率在多年和不同品种之间存在很大差异。显微镜下观察到了卵子，并且基于过程的模型进行的模拟表明，每年春季和初夏存在有利于卵子萌发的条件。共有409的P。葡萄对三年来收集的分离株进行了7种微卫星标记的基因分型，显示出非常高的基因型多样性，当与卵孢子的观察相结合时，表明有性繁殖种群。在409个分离株中，鉴定出225个多基因座基因型（MLG），其中仅检测到164个基因型，并且重复检测了61个（克隆）。多年来共检测到8个MLG（由28个分离株代表），表明P无性越冬的可能性。葡萄在这个地区。在整个采样日期中，属于非重复（独特）MLG的分离株的百分比范围为27.3％至63.2％。甚至在年度流行病快要结束时，未重复的MLG中分离株的比例仍然相对较高，约为30％。这些MLG可能起源于生长季节后期发芽的卵子，尽管不能完全排除早期采样不完全和移民造成的影响。