Abstract

Penicillium expansum causes severe rots on apple fruit during storage and shelf life. Aiming at the development of new antagonistic yeast active in controlling postharvest pathogens of fruit, several isolates were obtained from fig (Ficus carica) and cactus pear (Opuntia ficus-indica) grown in untreated orchards in Northern Sardinia (Italy). Two yeast strains of Candida guillermondii were selected for their remarkable antagonistic properties against P. expansum on apple. A film-forming strain of Saccharomyces cerevisiae isolated from wine was also included in the experiments. In trials carried out on the cv. Golden Delicious and Fuji, the yeasts applied alone or in the presence of various additives reduced apple rot with up to 100% efficacy. Killed yeast cells and culture filtrates had no biocontrol activity. Addition of different sugars in the apple wound had no detrimental effect on the biocontrol potential of the tested yeasts. Conversely, several nitrates significantly inhibited the antagonistic capability of C. guillermondii, thus suggesting that competition for nitrogen should play a major role in the biocontrol activity of the antagonistic yeast.

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