|ADIYAMAN, TUGBA - Ege University|
|Schisler, David - Dave|
|Slininger, Patricia - Pat|
|Rooney, Alejandro - Alex|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2010
Publication Date: 1/1/2011
Citation: Adiyaman, T., Schisler, D.A., Slininger, P.J., Sloan, J.M., Jackson, M.A., Rooney, A.P. 2011. Selection of biocontrol agents of pink rot based on efficacy and growth kinetics index rankings. Plant Disease. 95(1):24-30.
Interpretive Summary: The pathogen that causes pink rot disease on potatoes in the field and in storage is difficult to control. The organism that causes the disease has become increasingly resistant to chemical control methods and potato resistance to the disease is not very high. In this study, we used novel selection techniques to find naturally occurring microorganisms with potential to reduce or biologically control new infections of potatoes in storage. These potential biocontrol agents were evaluated not only for how well they reduced the disease, but also for their ability to generate a high quantity and quality of cells when produced in liquid culture. By selecting strains that grew well in liquid culture and produced effective biocontrol cells, we insured that the biocontrol strains we discovered had a strong potential for commercial development. Six strains of biocontrol agents were selected that significantly reduced pink rot disease in potato storage assays by as much as 33% when only a modest number of cells were applied to tubers. These results demonstrate that these newly discovered biocontrol agents can significantly reduce new pink rot infections in stored potatoes and that their further development should ultimately benefit potato growers, storage operators, and consumers.
Technical Abstract: The ineffectiveness of many fungicides against pink rot induced by Phytophthora erythroseptica, as well as a public desire for environmentally friendly chemical alternatives, calls for the development of biological control strategies. In this study, the microbiota of 84 different agricultural soils was individually transferred to separate samples of gamma irradiation-sterilized field soils enriched with potato periderm. After microbial community proliferation in similarly enriched field soil environments, samples of each were assayed for biological suppressiveness to P. erythroseptica-induced pink rot and zoospore production using tuber and soil extract assays. The 13 most suppressive soil samples, which reduced zoospore production by 14 to 93% and disease severity on tubers by 6 to 21%, were used to isolate over 270 bacteria and yeast. Fourteen strains that were superior in reducing new pink rot infections in preliminary tests were selected for further study. Six bacterial strains that significantly reduce the severity of pink rot (P greater than or equal to 0.05, FPLSD) were identified as Bacillus simplex (3 strains), Pantoea agglomerans, Pseudomonas koreensis, and Pseudomonas lini. Relative performance indices (RPIs) for the efficacy and for each of four kinetic parameters including total colony forming units (cfu/ml, CFUmax), biomass production values (DWmax), cell production after 8 hours (OD8), and time of nutrient depletion (DT) were calculated for each strain. In addition, overall RPI values for each strain were calculated by using the RPI values for both efficacy (RPIEff) and kinetics (RPIKin) obtained for each strain. Strains with the highest RPIEffKin possess both superior efficacy and liquid culture growth characteristics that suggest strong commercial development potential. Factors that can influence RPIEffKin and their associated rankings are discussed.