In vivo and in vitro potential of moringa oleifera leaf extract to retard post-harvest decay of tomato

Abstract

Tomato (Solanum lycopersicum) is among the world’s eight most valuable agricultural commodities, according to the Food and Agriculture Organization of the United Nations (FAO). However, postharvest losses of tomatoes caused by fungi are a major problem. Chemical fungicides have been widely used to control phytopathogenic fungi in tomatoes, despite their potential risks to human health and the environment. This issue can be addressed sustainably through the development of safer, eco-friendly alternatives such as plant-based biocontrol agents. This study aimed to investigate the antifungal activity of the ethanolic leaf extract of Moringa oleifera against three fungal species, Aspergillus flavus, A. niger and A. fumigatus isolated from contaminated tomatoes. The fungal isolates were cultured on potato dextrose agar (PDA) and identified through the microscope at the Biology Laboratory, South Eastern University of Sri Lanka. M. oleifera extracts were prepared using the maceration method. The antifungal activity was evaluated in vitro using the disk diffusion method to determine the minimum inhibitory concentration (MIC) antimicrobial susceptibility. Results revealed that ethanolic leaf extract of Moringa oleifera exhibited the maximum zone of inhibition, measuring 9.73±0.08mm against A. niger and the second-highest inhibition zone value against A. flavus which is 8.44±0.01mm and lowest inhibition zone against A. fumigatus is 6.87±0.05 mm. The minimum inhibitory concentrations of the extract were determined as 8.09 mg/ml for Aspergillus niger and Aspergillus flavus, and 16.18 mg/ml for Aspergillus fumigatus. Treated and untreated (control) tomatoes were observed in vivo over seven days to determine the disease severity on the fruit surface. Untreated tomatoes were severely damaged by A. niger, showing deep fissures likely resulting from rapid enzymatic degradation and tissue acidification. A. flavus induced localized epidermal breakdown, whereas A. fumigatus displayed lower natural virulence in healthy fruit tissues. M. oleifera extract was more effective against A. flavus and A. niger compared to A. fumigatus indicating difference in fungal virulence and infection behaviour.