Antifungal Potential of Chitosan and Phenyllactic Acid against Colletotrichum gloeosporioides, the Anthracnose Pathogen in Avocados

Avocado (Persea americana Mill.) is a tropical fruit with significant economic value worldwide. However, the avocado industry faces important challenges from anthracnose rot, caused by Colletotrichum gloeosporioides species, which affects negatively fruit quality and market value. Growing concerns about synthetic fungicides and consumer demand for safer alternatives drive interest in natural bioactive agents for postharvest disease control. This research assessed the in vitro antifungal efficacy of chitosan (CHI), phenyllactic acid (PLA), individually and in combination, against C. gloeosporioides isolated from Kenyan avocados. Through the poisoned food assay, both CHI and PLA significantly (P < 0.05) inhibited pathogen growth in a concentration-dependent manner. PLA completely (100%) inhibited mycelial growth and conidia germination at 4 mg/mL, while CHI achieved 78.82% inhibition of mycelial growth and 66.67% inhibition of conidia germination at 15 mg/mL. CHI-PLA mixtures exhibited an additive type of interaction (Abbott method) and caused significant morphological deformation of conidia. These findings highlight CHI-PLA mixtures as a promising and sustainable alternative to synthetic fungicides for managing postharvest anthracnose in avocados