Location: Crop Bioprotection Research
Project Number: 5010-22410-015-03-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jun 1, 2013
End Date: Mar 31, 2017
1. Evaluate and optimize superior inert and osmoprotectant compounds that promote survival and efficacy of three Pseudomonas strains highly effective in reducing dry rot in storage. 2. Assess efficacy and application methodology of biocontrol strains in small-scale commercial setting.
For the first objective, a microplate-based assay developed by ARS scientists at NCAUR will be used to test the suitability of inert and osmoprotectant compounds for individually formulating each of 3 P. fluorescens biocontrol strains. Strains will be grown in liquid culture, cells formulated and delivered as microdroplets to microplate wells, the droplets air-dried and the dried cells reconstituted after controlled environment storage. Using a plate-reading spectrophotometer, the highest rate of cell growth to a specified yield will then be determined and used to select formulating compounds superior in enhancing cell survival during drying. Osmoprotectant compounds will be tested at two or more concentrations. Engineering useful combinations of osmoprotectants in the rehydration stage (and potentially during drying) to promote rapid initial biocontrol agent growth at wound sites will also be initiated. A wounded potato assay of the bioefficacy of the rehydrated cells of each biocontrol agent will also be conducted in parallel with each microplate-based experiment at NCAUR to determine formulation impact (positive, negative, or neutral) on cell biocontrol efficacy. Final formulation ranking will be based on effectiveness in maintaining cell efficacy and economic feasibility of utilizing the optimal concentration discovered for each formulant. For the second objective, potatoes (single variety) will be wounded, inoculated with Fusarium sambucinum (50/50 mixture TBZ resistant and not), and stored at the cooperator's research facility. Inoculated tubers will be treated with various formulations of the biocontrol strains. Potatoes will be stored and assessed for dry rot decay and severity. The initial year will be proof of concept assessing the post-harvest application and efficacy of the biocontrol strains.