Exploring the cellular and ultrastructural impact of Cymbopogon martinii essential oil against postharvest fungal pathogens of papaya

Postharvest fungal infections significantly reduce the quality and marketability of papaya fruit, leading to substantial economic losses. Plant-derived essential oils (EOs) have gained attention as eco-friendly alternatives to synthetic fungicides due to their bioactivity and biodegradability. In this study, the antifungal potential of Cymbopogon martinii essential oil (CMEO) was evaluated against two major postharvest pathogens, Colletotrichum gloeosporioides and Fusarium longifundum. Gas chromatography–mass spectrometry (GC–MS) analysis identified 51 compounds representing 98.06% of the total oil, predominantly oxygenated monoterpenes. CMEO exhibited strong concentration-dependent antifungal activity, achieving complete mycelial growth inhibition at 1500 µg/mL for C. gloeosporioides and 1200 µg/mL for F. longifundum. Although its efficacy was lower than that of Bavistin fungicide, CMEO demonstrated significant antifungal potential. Mechanistic investigations revealed disruption of fungal membrane integrity, evidenced by reduced ergosterol content, increased leakage of cellular components (OD260), extracellular acidification, and severe morphological and ultrastructural damage observed through scanning and transmission electron microscopy. Overall, this study highlights the potential of CMEO as a natural antifungal agent and provides mechanistic insights supporting its application for sustainable postharvest disease management of papaya.