Improving plant stress resistance by growth-promoting bacteria and evaluating the improvements by volatile emissions

Background and scope Bacteria with plant growth-promoting characteristics (PGPB) are established components of biofertilizers. Certain PGPB can also contribute to improved plant tolerance of environmental and biotic stresses, but there is limited information on mechanisms of PGPB-induced increases in plant stress tolerance and associated changes in plant physiological traits. Available evidence Among stress-induced physiological modifications, stressed plants release a series of volatile organic compounds (VOC) that serve as infochemicals for non-stressed parts of the same plant, neighboring plants and other organisms. Furthermore, the magnitude of VOC emissions and emission blend composition provide information of stress status and elicitation of various secondary metabolic pathways. Strong positive relationships among stress severity and rate of stress VOC release have been observed in different plant species, but how plant stress volatile emissions are altered by PGPB is not well understood. In this article, we argue that monitoring stress volatile release provides a rapid non-invasive way to assess the improvement of plant stress resistance upon PGPB-inoculation. We highlight mechanisms by which PGPB can ameliorate stress in plant growth environment and induce acclimation responses, and discuss how PGPB harboring 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzyme can avoid excessive stress responses. We show that plants inoculated with ACC deaminase-containing PGPB have lower ethylene emissions and increased resistance to multiple stresses and that this is manifested in increased photosynthesis and reduced stress VOC emissions under diverse environmental challenges. Conclusion We conclude that gauging stress volatile release is a promising way for non-invasive screening of the degree of improvement of plant stress resistance conferred by PGPB.

Automated summary

In this article, the authors discuss the potential of monitoring stress volatile release as a non-invasive way to assess the improvement of plant stress resistance conferred by plant growth-promoting bacteria (PGPB). They highlight the mechanisms by which PGPB can enhance plant stress tolerance and induce acclimation responses, and show that PGPB harboring 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzyme can reduce stress responses and increase resistance to multiple stresses.