CLONING OF 1,3-BETA-GLUCANASE OF THE YEAST BIOCONTROL AGENT CANDIDA OLEOPHILA

Antagonistic microorganisms have been most extensively studied as an alternative control method for postharvest diseases of fruits and vegetables. The main obstacle facing the widespread use of these biocontrol agents is that the level of control provided under commercial conditions often falls short of chemical control. Enhancing the activity of biocontrol agents could be the most important factor in their success for controlling fruit diseases and their ultimate acceptance in commercial disease management. Despite 20 years’ research in the field of biological control of postharvest pathogens, a superior antagonist has yet not been found through conventional screening of the naturally occurring microflora. In our efforts to identify genetic traits of the yeast C. oleophila and determine their potential to enhance its biocontrol activity, we have found constitutive production of chitinase and glucanase by the yeast cells in culture and in planta. A primary hypothesis was that these cell-wall-degrading enzymes produced by the yeast antagonist, may be involved in the mechanism by which the yeast inhibits postharvest pathogens. A corollary to this hypothesis is that overexpressing the indigenous genes encoding these lytic enzymes in the yeast C. oleophila, would result in producing an antagonistic strain with enhanced biocontrol efficacy.