Rhizospheric volatilome in modulating induced systemic resistance against biotic stress: A new paradigm for future food security

Rhizospheric microbiome and their metabolites, interact with plants and contribute to plant health through hormonal modulation, the supply of mineral nutrition, and pathogen suppression. The rhizospheric chemical dialogues between the plants and rhizobiome mediated by microbial volatile organic compounds (MVOCs) act as a mediator of intra-and inter-species communication and plant defense, and they interfere with the signaling processes. The complex blend of volatiles in the rhizosphere comprises plant root volatiles, MVOCs, and their interaction-specific volatile cues. Regardless of the biological activities of MVOCs in the rhizosphere, there is limited knowledge of the molecular machinery involved in plant perception of MVOC. Plants lack olfactory organs; however, they perceive and react systematically to volatile stimuli. Therefore, VOC perception and signaling depend on basal protein families that define a universal language. Rhizospheric volatiles such as dimethyl di-sulfide, S-methyl thioacetate, methyl thiocyanate, undecane, linalool, dimethyl tri-sulfide, terpenes, tridecane, 2,3-butanediol, hydrogen cyanide, etc., are potent pathogen suppressors. MVOC blends of rhizosphere microbiome are suitable substitutes for harmful chemical pesticides and are newer bio-solutions for disease management. The volatile-based electronic noses detect microbe-induced plant volatiles in a precise and noninvasive manner, enabling rapid plant disease diagnosis. This review summarizes the current trends of MVOCmediated plant protection against biotic stress, emphasizing the signaling pathways and hormonal modulation. The functional role of MVOCs in the rhizosphere as an info-chemical and in recruiting beneficial microbiome are also discussed. Understanding the mechanisms of MVOCs as weapons against plant pathogens as well as the translational potential of such volatiles as eco-friendly biocontrol solutions open new avenues for designing smart bio-formulations. The major challenges to harnessing the power of volatiles or their emitters for better insights into the regulation of MVOC emission in the natural environment have been highlighted.

Automated summary

The rhizospheric microbiome and their metabolites interact with plants, contributing to plant health through hormonal regulation, nutrient supply, and pathogen suppression. Chemical dialogues mediated by microbial volatile organic compounds (MVOCs) act as a mediator of communication and defense between plants and the rhizobiome, interfering with signaling processes. Volatile compounds in the rhizosphere, such as dimethyl di-sulfide, linalool, and hydrogen cyanide, have potent pathogen-suppressing abilities and can serve as eco-friendly alternatives to chemical pesticides. Volatile-based electronic noses enable rapid and noninvasive plant disease diagnosis.