Project Number: 3620-22410-011-06
Project Type: Specific Cooperative Agreement

Start Date: Jul 07, 2009
End Date: May 31, 2012

Objective:
1) Rank newly discovered antagonists of pink rot from bioprospecting program for amenability to both economical production and efficacy in laboratory tests when produced using commercially tenable liquid culture protocols. 2) Assay highly ranked, superior biocontrol candidates identified in Objective 1 alone or in combination with pesticides in small pilot-scale tests under commercial potato storage conditions with University of Idaho collaborators in Kimberly, Idaho.

Approach:
Objective 1: Promising antagonists of pink rot have been isolated from suppressive microbial communities taken from potato soil samples collected by cooperators in Washington, Idaho and Wisconsin. Soil samples were processed at NCAUR via transferring small amounts of live soil samples to aliquots of a gamma irradiation-sterilized potato production soil enriched with sterilized potato periderm and Phytophthora erythroseptica mycelia and allowing microbial community proliferation to take place in the resultant common sterile soil background. In the currently proposed research, pure cultures of putative antagonists will be assayed for suppression of sporangia production, zoospore liberation and pink rot disease development using whole tuber bioassays conducted at NCAUR. The growth kinetics of these strains (such as logarithmic growth rate, maximum biomass accumulation, absorbance maximum) also will be determined in liquid culture by NCAUR, USDA-ARS. Relative performance indices (RPI’s) based on strain efficacy and kinetics performance data will be calculated and used to rank strains as to their commercial development potential with highest ranks being achieved by strains possessing both favorable efficacy and growth kinetics in commercially feasible liquid culture media. Objective 2: Strains identified as possessing both efficacy against pink rot and favorable liquid culture growth kinetics will be tested alone or in combination with reduced levels of pesticides for efficacy in reducing pink rot in small pilot-scale field tests (randomized complete block designs) in Kimberly, ID,University of Idaho. State of the art potato storage facilities at this location will be utilized where commercial storage house parameters of air flow, temperature ramping, relative humidity and CO2 levels will be controlled to simulate commercial storage house conditions. Superior microbial antagonists that are amenable to commercial-scale liquid culture production techniques will be produced in benchtop fermentors charged with commercially feasible liquid media at ARS laboratories in Peoria, IL, and tested for efficacy in reducing pink rot on two or more potato varieties in Kimberly, ID, and Peoria, IL. Experiments will be conducted at least twice in each storage location. A second year of funding at similar levels to those described below would allow the development of optimized fermentation and formulation protocols to enhance the effectiveness of biocontrol strains discovered in the work. Techniques would also be developed and tested under field conditions to determine if effective strains reduce pink rot in the field when used alone or in combination with chemicals to treat cut seed pieces prior to planting. This proposed research on developing antagonists active against pink rot disease on stored potato tubers directly addresses needs for discovering novel biocontrol agents described in Problem Statement 4A (Biological and Cultural Control Technologies) of the Action Plan for ARS NP303.