UV protectants for Candida oleophila (strain O), a biocontrol agent of postharvest fruit diseases

Abstract

This study investigated the influence of UV-B radiation (280-320nm) on survival of Candida oleophila strain O, an antagonist yeast that prevents postharvest diseases caused by Botrytis cinerea and Penicillium expansum on apple and pear fruits. Lethal doses (LD50 and LD90) were, respectively, 0·89 and 1·45Kjm-2 for in vitro exposure and 3·06 and 5·5Kjm-2 for in vivo exposure. A screening test of UV-B protectants for strain O was also evaluated under in vitro and in vivo conditions. The in vitro results showed that sodium ascorbate (0·1% and 0·01%), riboflavin (0·1%) and uric acid (0·1% and 0·01%) were the most effective and most suitable protectants. However, only riboflavin (0·1%) and uric acid (0·1%) were effective under in vivo conditions. The efficacy obtained with strain O against P. expansum, when subjected to UV-B radiation, was 75·0% and 49·2% for pathogen concentrations of 105 and 106sporesmL-1, respectively. Adding riboflavin to strain O gave a similar efficacy (64·2%). Applying strain O together with uric acid (0·1%) was less active (47·7%). Nonetheless, its efficacy when applied with the antioxidants sodium ascorbate (71·1%) or ascorbic acid (82·5%) was the greatest. Riboflavin and uric acid were the most cost-effective protectants, and could be included in the final formulation of strain O when applied preharvest. © 2010 The Authors. Plant Pathology © 2010 BSPP.