Antifungal volatiles from medicinal herbs suppress Fusarium oxysporum f. sp. lycopersici

Medicinal herbs are the potential sources for antimicrobial compounds against soil-borne pathogens. The present investigation focuses on assessing the efficacy of antifungal activity of volatile organic compounds (VOCs) produced by seven different medicinal herbs in the suppression of F. oxysporum f.sp. lycopercisi, the causal agent of wilt disease in tomato plants. Among the seven samples tested in-vitro, the blend of VOCs emitted from mint (Mentha spicata) leaves inhibited the mycelial growth of F. o. f.sp. lycopercisi up to 41.88% followed by lemongrass (39.44%) and nochi leaves (34.66%). The important VOCs emitted by mint and lemongrass samples were identified through Headspace – Gas chromatography coupled with Mass Spectrophotometry (HS-GCMS) which revealed the presence of around 25 different compounds with varied functional groups. Among them -(-) carvone obtained from mint leaves had the highest relative abundance (2.08% peak area at 10.25 RT). In addition, geraniol and citronellol were also present with a peak area percentage of 15.85 at 10.37 RT and 5.27 at 9.97 RT, respectively. Pure compounds of carvone, geraniol and citronellol (Sigma Aldrich) along with plant samples were also tested in vitro for comparison on the inhibition of mycelial growth of F. oxysporum f. sp. lycopercisi. Among the samples, citronellol was found to be the most effective and suppressed the wilt pathogen up to 100% at 500 ppm, followed by carvone (up to 90% inhibition) in the partition plate method. The results indicated that VOCs produced from mint and lemongrass could be explored with an additive effect for the management of F. oxysporum f.sp. lycopercisi along with other Integrated Disease Management (IDM) practices.