ARS | Publication request: Podosphaera xanthii but not Golovinomyces cichoracearum infects Cucurbits in a Greenhouse at Salinas, California

Submitted to: Cucurbit Genetics Cooperative Report
Publication Type: Research Notes
Publication Acceptance Date: June 1, 2011
Publication Date: May 1, 2012
Citation: Bojorques Ramos, C., Maruthachalam, K., Mccreight, J.D., Garcia Estrada, R.S. 2012. Podosphaera xanthii but not Golovinomyces cichoracearum infects Cucurbits in a Greenhouse at Salinas, California. Cucurbit Genetics Cooperative Report. 33-34:24-28.

Technical Abstract: Two fungal species are the primary causes of cucurbit powdery mildew (CPM): Podosphaera xanthii and Golovinomyces cichoracearum. CPM on melon (Cucumis melo L.), cucumber (C. sativus L.) and summer squash (Cucurbita pepo L.) in a greenhouse at Salinas, California in winter 2011 was confirmed to be incited by P. xanthii based on several morphological and molecular criteria. Golovinomyces cichoracearum, which is known to incite CPM in other countries but not in the United States, also incites powdery mildew on lettuce (Lactuca sativa L.) worldwide. Previous research at Salinas demonstrated G. cichoracearum from lettuce did not infect melon. In winter 2011, lettuce grown adjacent to the cucurbits was infected by G. cichoracearum, but the fungus was not observed to infect melon, cucumber or summer squash in the same greenhouse during the same period of time. Controlled inoculations of cucumber were negative for infection; conidial germination on cucumber was typical for powdery mildew pathogens on non-host species.