Volatile-mediated inhibition of Fusarium wilt in pigeonpea conferred by Bacillaceae members isolated from the host plant’s rhizosphere

Abstract

Background and aim: Different biotic and abiotic stresses in agriculture restrict crop productivity, leading to dwindling biomass. Conventional bioinoculants have lost farmers' confidence due to reduced persistence under natural conditions. The understanding of mechanisms underlying suppression of phytopathogens remains a key challenge in developing effective biocontrol strategies. The current study assessed bacterial volatilomes for their ability to inhibit the fungal pathogen Fusarium udum in pigeonpea and also to characterize the chemical dialogue underlying the interaction between the pathogen and the biocontrol strains. Methods and results: The effects of bacterial volatiles on Fusarium wilt in pigeonpea investigated through in planta assays, applied before and after infection, revealed both direct, antifungal effects, and indirect, plant immunity-mediated effects. The potential dialogue between the biocontrol strains and F. udum, studied by monitoring the changes in bacterial volatile emission in strains exposed to the volatiles of the phytopathogenic fungus using connected microcosms, led to the identification of bacterial volatiles whose emission was upregulated upon exposure to F. udum. Applying these as synthetic compounds resulted in successful mitigation of Fusarium wilt in pigeonpea. Conclusion: The volatile organic compounds (VOCs) emitted by native members of the pigeonpea (Cajanus cajan L. Millsp.) microbiota effectively protected this crop against vascular wilt caused by F. udum under controlled conditions. Further, the potential of synthetic volatiles was demonstrated as effective biocontrol strategy, providing a promising alternative to chemical pesticides and inconsistent conventional bioinoculants.