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Poster: Biology & Disease Mgmt: Biological Control


Evaluation of the biocontrol potential of different Pseudomonas species in suppressing Pythium root rot in petunia plugs
D. MARTIN (1), M. Jones (2), C. Taylor (2), F. Peduto Hand (1) (1) The Ohio State University, U.S.A.; (2) The Ohio State University, U.S.A.

Pythium spp., causing root rot and damping off, affects 300+ hosts including several ornamental plants, and has developed resistance to two widely used fungicides, mefanoxam and propamocarb. This poses a real threat to greenhouse growers’ efficiency in cultivating healthy plants. Ohio State researchers have identified several Pseudomonas strains that exhibit biological control potential for disease suppression in many crops, including corn and tomato. One strain of each of the species P. putida, P. brassicacearum, P. fluorescens, P. poae and P. protegens was tested for the ability to suppress the activity of different Pythium species in petunia plugs. Since the production of bacterial metabolites is higher in the transition between logarithmic and stationary phases, our first step included building growth curves of the five strains to identify the appropriate time needed for incubation of the bacterial inoculum prior to application to petunia plugs. Cultures were prepared in LB medium and the OD600 values were recorded using a spectrophotometer every two hours for up to 18 hours. Serial dilution plating at each time point provided correspondent CFUs. ‘Carpet White’ Petunia seeds were sown in 128-plug trays and immediately treated with a 107 CFU/mL concentration of each Pseudomonas strain. After 14 days, plugs were inoculated with the different Pythium species. Responses of disease incidence and severity were evaluated until plugs became shipment-ready.