Phytohormones mediated antifungal resistance against Fusarium oxysporum

This study aims to evaluate the in vitro as well as in vivo antifungal activities of different phytohormones (PHs) against the hemibiotroph fungus, Fusarium oxysporum using black gram [Vigna mungo (L.) Hepper] as a model system. The potential antifungal activities were tested using PHs viz. salicylic acid (SA), methyl jasmonate (MeJA), melatonin (MT), brassinolide (BL), indole-3-acetic acid (IAA), gibberellic acid₃ (GA₃), ethephon (ET), and abscisic acid (ABA), by determining the minimum inhibitory concentration (MIC) and minimum effective concentration (MEC) end point in a microtiter plate-based assay. The results suggested significant antifungal activity for all the tested PHs, wherein SA and MeJA showed potency even at the lowest concentration tested, with corresponding MIC₉₀ values of 0.312 mM and 0.625 mM, respectively. Likewise, a similar MEC profile was also observed for both SA and MeJA, with a corresponding value of 0.078 mM and 0.312 mM, respectively. The microtiter results were corroborated using spore germination and mycelial susceptibility assays. The in vivo antifungal efficacy of PHs was assessed by recording the germination characteristics in SA and MeJA-primed V. mungo seeds that were already exposed to F. oxysporum spores. The PHs-primed seeds displayed a characteristic longer seedling length and higher seed vigor index (SVI), in concomitant with relative enhanced ROS-scavenging activity. The priming of V. mungo seeds with SA and MeJA seems to induce a defense mechanism against F. oxysporum infection, which also improved its germination characteristics.