Pilot testing of Kloeckera apiculata for the biological control of postharvest diseases of citrus

The efficacy of the yeast Kloeckera apiculata, strain 34-9, in controlling postharvest decay of citrus fruit was evaluated in small-scale and pilot tests in commercial packinghouse. Kloeckera apiculata grew efficiently on different media and maintained its antagonistic activity against spore germination of Penicillium italicum. In small-scale experiments with citrus fruits dipped in the yeast cell suspension, the development of decay in citrus was effectively inhibited. The yeast was compatible with a mixture of low concentration of a commonly chemical fungicide. In packinghouse tests, combining the yeast with 40 mg/kg Carbendazim (MBC) resulted a reduction in the incidence of decay to a level equal to that of the commercial treatment of 200 mg/kg MBC. The efficacy of the strain 34-9 could also be maintained under packinghouse conditions at a cell concentration of the yeast antagonist as low as 10(6) cells/ml. No significant difference in the efficacy of K, apiculata was found in either the drench or the spray application systems tested in citrus packinghouse. Scanning electron microscopy revealed attachment of the yeast cells to the pathogen hyphae. The high antagonistic activity of strain 34-9 against citrus blue mould may be related to its capability to compete with Penicillium italicum, for space and nutrients and/or involvement of directly antagonist of the yeast on the fungus.