Bacterial volatiles for plant growth

Abstract

The rhizosphere is defined as the zone of soil surrounding the plant roots. Plant roots secrete a variety of plant exudates rich in nutrients resulting in accumulation of more bacteria in the rhizosphere region, generally 10-100 times higher than in the bulk soil. The bacteria colonizing this rhizosphere region are called as rhizobacteria, and those which help in promoting the growth of plants are called as plant growth-promoting rhizobacteria (PGPR). Currently, many biological approaches have gained importance for improving the crop production. One of the approaches includes using microbes as bioinoculants to promote growth and development of plants. Many rhizobacteria are presently being used as bioinoculants. They possess different mechanisms to enhance the plant growth such as nitrogen fixation, phosphate solubilization, production of siderophores, production of 1-aminocyclopropane-1-carboxylate deaminase (ACC), phytohormone production exhibiting antifungal activity, quorum sensing (QS) signal interference, induction of systemic resistance, interference with pathogen toxin production, and production of volatile organic compounds (VOCs). The production of VOCs by microorganisms can be considered as a novel characteristic property of PGPR in promoting the plant growth. The chemicals produced by microorganisms like bacteria and fungi as a part of their metabolism are called as microbial volatile organic compounds (MVOCs). These can modulate the physiology of plants and microorganisms and thus can provide an alternative method to use of chemicals in protecting plants from pathogens and increasing crop yield. MVOCs can be considered as ecofriendly and cost-effective strategy for sustainable agriculture.