Screening antagonistic yeasts against citrus green mold and the possible biocontrol mechanisms of Pichia galeiformis (BAF03).

BACKGROUND: Penicillium digitatum is one of the most important pathogens causing citrus green mold, leading to significant economic losses. Traditionally, synthetic fungicides are used to control diseases. However, the side effects of fungicides should not be ignored. Thus, antagonistic yeasts were proposed to be safe and effective alternatives to manage diseases. Orchards are excellent sources of naturally occurring antagonists against pathogens. Therefore, antagonistic yeasts obtained from orchards were screened, and the possible biocontrol mechanisms of the most promising yeast were investigated. RESULTS: Seventy-eight isolates of yeasts (15 species of 10 genera) were obtained from citrus orchards. In in vitro assays, 16 strains showed antifungal activity against P. digitatum and 15 strains showed biocontrol potential against green mold on Olinda oranges. Pichia galeiformis (BAF03) exhibited the best antagonistic activity against P. digitatum during 6 days storage at 25 degrees C and a good antagonistic activity during 29 days at 4 degrees C. P. galeiformis (BAF03) could colonize and amplify quickly in wounded citrus. Scanning electron microscopy (SEM) results showed that the citrus wound was colonised by the yeast. A total of 8 VOCs were identified by Gas Chromatography-Mass Spectrometry (GC-MS). The volatile organic compounds (VOCs) produced by P. galeiformis (BAF03) efficiently inhibited P. digitatum. CONCLUSION: P. galeiformis (BAF03) isolated from a citrus orchard showed potential to control postharvest green mold of citrus. The possible mechanisms of action likely include competition for space and nutrients as well as production of VOCs. This article is protected by copyright. All rights reserved.