Diversity of Species Recovered from Float-Bed Tobacco Transplant Production Greenhouses.

Pythium diseases are common in hydroponic crop production and often threaten the greenhouse production of cucumber, tomato, lettuce, and other crops. In tobacco transplant production, where float-bed hydroponic greenhouses are commonly used, Pythium diseases can cause up to 70% seedling loss. However, there have been few comprehensive studies on the composition and diversity of communities in tobacco greenhouses. In a 2017 survey, 360 isolates were collected from 41 tobacco greenhouses across four states (VA, MD, GA, and PA). Samples were collected from one to seven sites within each greenhouse. Twelve described species were identified (, , , , , , , , , , , and ) among the isolates obtained. Approximately 80% of the surveyed greenhouses harbored in at least one of four sites (bay water, tobacco seedlings, weeds, and center walkways) within the greenhouse. The structure of communities was diverse among the surveyed greenhouses: multiple species coexisted in the same sample, and multiple species were present within the same greenhouse at different sites. This diversity appeared to be influenced by the sampling sites within the surveyed tobacco greenhouses, sample type, and sampling time. Intraspecific variation may also exist among the populations found in this study. These results uncovered the complexity and diversity of the communities within float tobacco transplant greenhouses, which could play a role in the variation in Pythium diseases observed in these production systems.