Biocontrol potential of killer yeasts to manage postharvest decay of orange fruits

Abstract

Abstract Yeasts are some of the most important postharvest biocontrol agents (BCAs). Postharvest orange fruits frequently deteriorate due to green and blue rot, leading to significant economic losses. The aim of this study was to isolate phytopathogenic moulds from infected orange fruits, to evaluate the ability of killer yeasts isolated from healthy orange fruits and leaves of orange orchards to control phytopathogenic moulds and their effectiveness under different stress conditions, to evaluate the additive effect of BCAs in combination with 2% sodium bicarbonate (SBC), 2% sodium benzoate (SB), 2% calcium chloride (CaCl2), 0.2% salicylic acid (SA) or 0.5% chitosan, to detect the action mechanisms of the most potent yeasts and formulation of the most potent antagonist as a postharvest application. Among eleven mould isolates, two isolates were identified as P. digitatum and P. italicum and selected for in vitro assays. Twenty -eight yeast isolates were obtained exhibited high killer activity. Twelve isolates reduced 22.4 –68.8% of P. digitatum growth while seven isolates reduced 21.1- 68.5% of P. italicum growth. The most potent yeast isolates were identified as Candida pseudotropicalis, C. salmanticensis, C. membranifaciens and Pichia guilliermondii. Pichia guilliermondii and C. salmanticensis demonstrated a great potential as biocontrol agents against P. digitatum and P. italicum, under a wide range of the studied environmental stress conditions. Combination of C. pseudotropicalis, and P. guilliermondii with SBC, CaCl2 or chitosan increased their effectiveness against P. digitatum, while combination of C. pseudotropicalis, C. salmanticensis and P. guilliermondii with these additives decreased their effectiveness except C. salmanticensis enhanced with SBC against P. italicum.