Cespedes-Sanchez M C, Naegele R P, Kousik C S, Hausbeck M K
Former Graduate Research Assistant.
Research Associate, Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing 48824.
Plant Dis. 2015 May;99(5):676-682. doi: 10.1094/PDIS-05-14-0500-RE.
Downy mildew, caused by Pseudoperonospora cubensis, is a severe foliar disease of many cucurbit crops worldwide. Forty-one cucurbit cultigens (commercial cultivars and plant introductions) from five genera (Cucumis, Citrullus, Cucurbita, Lagenaria, and Luffa) were assessed for susceptibility to P. cubensis in a research field exposed to natural inoculum in Michigan. Eight cultigens from a differential set for pathotype determination were included within the 41 cultigens to detect changes in dominant P. cubensis pathotypes present. No pathotype differences were found between 2010 and 2011. Cucumis melo cultigen MR-1 was less susceptible to Michigan P. cubensis populations than other C. melo cultigens. No symptoms or signs of infection were detected on cultigens of Cucurbita moschata and C. pepo. Disease onset was later in 2011 than 2010; greater than 90% disease severity in pickling cucumber 'Vlaspik' was observed in both years. This study confirmed that Cucumis is the most susceptible cucurbit genus, while Citrullus and Cucurbita cultigens were the least susceptible genera to populations of P. cubensis in Michigan. Area under the disease progress curve values indicated that disease progress was limited on all Citrullus cultigens compared with Cucumis cultigens, and pathogen sporulation was not detected under field conditions. Future studies should evaluate the ability of a reduced fungicide program to control downy mildew on less susceptible Cucumis melo 'Edisto 47', 'Primo', 'Athena', 'Strike', 'Ananas', 'Banana', and 'Tam-Dew'. Many of the melon cultivars evaluated were selected on the basis of reported resistance to downy mildew, yet they showed significant disease symptoms. It is important to evaluate candidate cultigens for resistance to local P. cubensis populations.
霜霉病由古巴假霜霉菌引起，是全球许多葫芦科作物严重的叶部病害。在密歇根州一块暴露于自然接种体的研究田地里，对来自五个属（黄瓜属、西瓜属、南瓜属、丝瓜属和棱角丝瓜属）的41种葫芦科栽培品种（商业品种和引进植物）进行了对古巴假霜霉菌的敏感性评估。在这41种栽培品种中纳入了8种用于致病型测定的鉴别品种组品种，以检测优势古巴假霜霉菌致病型的变化。2010年和2011年之间未发现致病型差异。黄瓜栽培品种MR-1比其他甜瓜栽培品种对密歇根州的古巴假霜霉菌种群更具抗性。在南瓜和西葫芦的栽培品种上未检测到感染症状或迹象。2011年病害发生时间比2010年晚；在两年中，腌制黄瓜“Vlaspik”的病害严重程度均超过90%。本研究证实，黄瓜属是最易感的葫芦科属，而西瓜属和南瓜属栽培品种对密歇根州的古巴假霜霉菌种群最不易感。病害进展曲线下面积值表明，与黄瓜属栽培品种相比，所有西瓜属栽培品种的病害进展有限，并且在田间条件下未检测到病原菌产孢。未来的研究应评估减少杀菌剂方案对控制较不易感的甜瓜品种“Edisto 47”“Primo”“Athena”“Strike”“Ananas”“Banana”和“Tam-Dew”上霜霉病的能力。所评估的许多甜瓜品种是根据报道的对霜霉病的抗性选择的，但它们仍表现出明显的病害症状。评估候选栽培品种对当地古巴假霜霉菌种群的抗性很重要。
