Enhancement of the biocontrol agent Candida oleophila (strain O) survival and control efficiency under extreme conditions of water activity and relative humidity

Plant Pathology Unit, Gembloux Agricultural University, Passage des Déportés 2, 5030 Gembloux, Belgium; Plant Biology Research Institute, Department of Biological Sciences, Montreal University, 4101 Sherbrooke Est, Montréal, Que., H1X 2B2 Canada; Received 20 May 2008. Accepted 23 July 2009. Available online 29 July 2009.
Biological Control (Impact Factor: 1.87). 12/2009; 51:403-408. DOI: 10.1016/j.biocontrol.2009.07.014

ABSTRACT The objective of this work is to evaluate the ability of some additive substances in protecting the biocontrol agent Candida oleophila (strain O) against the adverse effects of environmental factors, such as water activity (aw, 0.93 and 0.98) and relative humidity (75% and 98%). The protection obtained with various protectant substances, skimmed milk (SM), peptone, maltose, sucrose, sorbitol, lactose and polyethylene glycol was assayed under in vitro and in vivo conditions. The yeast cells with the highest level of protecting agents (1%) had higher viability than those with low protectant levels (0.1% and 0.5%). SM, sucrose and sorbitol improved significantly the C. oleophila survival on apple fruit surface by 80.8%, 42.26% and 37.27% and gave a significant protection (from 96% to 100%) against Penicillium expansum under dried conditions. The highest strain O density and efficacy was obtained with SM. Under experimental conditions reflecting practical conditions, SM applied in combination with the strain O resulted in improved biocontrol efficacy by 74.65%. Therefore, SM could be used as material substrate with the best sugar protectants during the formulation process of this antagonistic yeast for eventual pre-harvest application.

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