APPLICATION OF CANDIDA-GUILLIERMONDII IN COMMERCIAL CITRUS COATINGS FOR BIOCONTROL OF PENICILLIUM-DIGITATUM ON GRAPEFRUITS

Candida guilliermondii was evaluated for compatibility with commercial citrus coatings for application to heat-treated grapefruits (Citrus paradisi Macf.) and biological control of Penicillium digitatum. Although constituents of many coatings were fungicidal, FMC 705 and FMC 214 (FMC Corp., Lakeland, FL) and Nature Seal (USDA product) were satisfactory carriers for the yeast. Candida guilliermondii survived for 2 months at 13-degrees-C within films of dried coatings on filter paper disks. When applied to grapefruits in FMC 705 or Nature Seal at concentrations calculated to produce initial surface populations of 10(4) or 10(6) cfu/cm2, the populations stabilized over 9 weeks at 13-degrees-C between 10(5) and 10(6) Cfu/CM2. Populations of unidentified, native Candida species on fruits were originally 3 x 10(2) cfu/cm2 before a 3-h quarantine treatment in air at 48-degrees-C reduced them to 2 x 10(1). Although these low native populations on heated fruits subsequently rebounded over 9 weeks to levels approximately 10(4) Cfu/CM2, fruits to which C. guilliermondii was applied remained free of decay 12 to 20% longer in cold storage than fruits not treated with this species. (C) 1994 Academic Press, Inc.