Biocontrol potential of plant extracts against <i>Fusarium oxysporum</i> ‐induced fruit rot in tomato

Abstract Tomato ( Solanum lycopersicum L.) is one of the most consumed vegetables globally. However, it is highly susceptible to fruit rot disease, with Fusarium oxysporum being one of the primary causal pathogens. The frequent and unselective use of synthetic fungicides to control this disease has led to the development of resistant fungal strains and the accumulation of harmful residues in fruits. This study aimed to screen antifungal activity of selected plant extracts against F. oxysporum under in vitro conditions and to evaluate their efficacy in controlling fruit rot in tomatoes. Plant extracts were prepared using various solvents, and their antifungal activity was initially assessed through a poisoned food bioassay. Eight out of 48 plant extracts exhibited significant inhibition of F. oxysporum mycelial growth. These eight extracts were subsequently tested for their effects on conidial germination. Among them, ethanolic extracts of Garcinia mangostana pericarp and Averrhoa bilimbi fruit significantly suppressed conidial germination compared to the controls. When applied to inoculated tomato fruits, both extracts, at different concentrations, effectively reduced disease severity. Particularly, G. mangostana pericarp extract at 100 mg/mL demonstrated comparable efficacy to the commercial fungicide carbendazim in suppressing fruit rot symptoms. Moreover, treatment with G. mangostana extract resulted in tomatoes with the lowest colour change (∆ E *), reduced sweetness, and highest firmness, indicating preserved fruit quality. To broaden the scope of application, the most effective treatments were also evaluated in vivo against other fruit rot pathogens, namely F. proliferatum , Colletotrichum gloeosporioides , and Lasiodiplodia theobromae . These trials showed varying levels of disease severity reduction depending on the treatment and pathogen. Overall, the findings highlight the potential of G. mangostana pericarp extract as an eco‐friendly alternative for managing fruit rot, particularly that caused by F. oxysporum .