Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC 27695-7613.
Phytopathology. 2021 Feb;111(2):312-320. doi: 10.1094/PHYTO-06-20-0231-R. Epub 2021 Jan 16.
is an obligate oomycete and cause of cucurbit downy mildew (CDM), the most destructive foliar disease affecting cucurbit hosts. Annual epidemics develop throughout the United States as windborne sporangia travel great distances and survive prolonged exposure to solar radiation. Recent genomic evidence suggests that isolates display host adaptation based on their respective clade. Early detection is key for fungicide application timing, and identification of the host-adapted clade provides information on the risk of infection for specific cucurbit crops. In this study, a multiplex quantitative PCR assay was developed based on species- and clade-specific nuclear genomic markers. The assay detected as few as 10 sporangia or DNA at 100 fg/ml for both clades and was validated in the field by deploying rotorod spore samplers in cucurbit sentinel plots located at two research stations in North Carolina. Using this assay, sporangia DNA was detected in spore trap sampling rods before signs of or CDM symptoms were observed in the sentinel plots. Both clade 1 and clade 2 DNA were detected in late-season cucumber and watermelon plots but only clade 2 DNA was detected in the early-season cucumber plots. These results will significantly improve disease management of CDM by monitoring inoculum levels to determine the cucurbit crops at risk of infection throughout each growing season.
是一种专性卵菌，可引起瓜类霜霉病（CDM），这是影响瓜类宿主的最具破坏性的叶部病害。随着风传的孢子远距离传播并在长时间暴露于太阳辐射下存活，美国各地每年都会发生流行病。最近的基因组证据表明，基于各自的进化枝， 分离株表现出宿主适应性。早期检测是施药时机的关键，而宿主适应性进化枝的鉴定为特定瓜类作物的感染风险提供了信息。在这项研究中，基于种和进化枝特异性核基因组标记，开发了一种多重定量 PCR 检测方法。该检测方法可检测到每 100 fg/ml 低至 10 个孢子或 DNA，两个进化枝均适用，并且在北卡罗来纳州的两个研究站的瓜类哨兵田块中，通过部署旋转杆孢子采样器在田间得到了验证。使用该检测方法，在哨兵田块中观察到 或 CDM 症状之前，在孢子陷阱采样棒中就检测到了孢子 DNA。在黄瓜和西瓜的晚季田块中检测到了进化枝 1 和进化枝 2 的 DNA，但仅在早季黄瓜田块中检测到进化枝 2 的 DNA。这些结果将通过监测接种体水平来显著改善 CDM 的疾病管理，以确定整个生长季节中易受感染的瓜类作物。
