Abstract
Alternaria alternata and Alternaria citri are two major pathogens affecting sweet cherries and citrus respectively which can lead to significant postharvest losses. Alternaria sp. can be controlled with synthetic fungicides, but due to the development of resistance and the need to find sustainable disease control solutions, alternative control measures need to be developed. We have previously shown that extracts derived from lemon waste (pomace) contain bioactive compounds with high levels of antioxidant, antifungal, and antibacterial activities. The aim of this study was to investigate the in vitro antifungal activity of lemon waste aqueous extracts at different concentrations (14, 7, 3.5 and 1 mg mL(-1)) against both A. alternata and A. citri. The results showed that lemon aqueous extracts suppressed the mycelial growth and spore germination of both species in a concentration-dependent manner. The mycelial growth inhibition (MGI) for A. alternata varied between 31 to 68%, while for the A. citri the MGI varied between 14 to 49%. Scanning electron microscopy showed that lemon waste extracts affected the morphology of both species.These results indicate that the aqueous extracts of lemon by-products contain bioactive compounds which could be potentially useful as an alternative to synthetic fungicides for controlling Alternaria.
