Bacterial volatiles in promotion of plant under biotic stress

Abstract

Confined to a narrow region but rich in nutrients, rhizosphere is always favorable to interactions between microorganisms and plants. While many soil microorganisms have no obvious effects on plants, some have negative as well as positive effects on plant growth. Plant growth-promoting rhizobacteria (PGPR) are beneficial microbes which have been fruitfully applied in agriculture to enhance seedling emergence, plant weight, crop yield, and disease resistance. Among these, some PGPR strains mediate plant growth promotion in direct and/or indirect manner by releasing volatile organic compounds (VOCs). Bacteria emitted a wide array of volatiles ranging from inorganic such as hydrogen cyanide (HCN) and nitric oxide (NO) to organic such as hydrocarbon, ketone, acids, terpenes, etc. Bacterial VOCs promote plant growth by eliciting different signaling pathway and show correlation with plant growth hormones also. In particular, 2,3-butanediol and acetoin were reported for the heightened level of plant growth promotion and triggering induced resistance against fungal pathogens. This chapter focuses on recent research study and role of bacterial volatiles in plant growth promotion and protection against pathogens.