Abstract
Bacterial volatiles play a significant role in promoting plant growth by regulating the synthesis or metabolism of phytohormones. In vitro and growth chamber experiments were conducted to investigate the effect of volatile organic compounds (VOCs) produced by the plant growth promoting rhizobacterium Bacillus subtilis strain SYST2 on hormone regulation and growth promotion in tomato plants. We observed a significant increase in plant biomass under both experimental conditions; we observed an increase in photosynthesis and in the endogenous contents of gibberellin, auxin, and cytokinin, while a decrease in ethylene levels was noted. VOCs emitted by SYST2 were identified through gas chromatography-mass spectrometry analysis. Of 11 VOCs tested in glass jars containing plants in test tubes, only two, albuterol and 1,3-propanediole, were found to promote plant growth. Furthermore, tomato plants showed differential expression of genes involved in auxin (SlIAA1. SlIAA3), gibberellin (GA20ox-1), cytokinin (SlCKX1), expansin (Exp2, Exp9. Exp 18), and ethylene (ACO1) biosynthesis or metabolism in roots and leaves in response to B. subtilis SYST2 VOCs. Our findings suggest that SYST2-derived VOCs promote plant growth by triggering growth hormone activity, and provide new insights into the mechanism of plant growth promotion by bacterial VOCs.
Highlights
Volatile organic compounds (VOCs) produced by plant growth promoting rhizobacterium (PGPR) have been proved to have the potential to control plant pathogens, to stimulate plant growth, and to induce systemic disease resistance (Ryu et al, 2003; Lee et al, 2012; Park et al, 2015; Raza et al, 2016; Tahir et al, 2017)
The plant growth promoting potential of VOCs produced by B. subtilis SYST2 was examined by growing plants in airtight tissue culture tubes exposed to SYST2 VOCs for 14 days
A significant increase was observed in fresh green weight, dry weight, leaf area, and root and shoot length of tomato plants exposed to SYST2 VOCs as compared to the control
Summary
Volatile organic compounds (VOCs) produced by plant growth promoting rhizobacterium (PGPR) have been proved to have the potential to control plant pathogens, to stimulate plant growth, and to induce systemic disease resistance (Ryu et al, 2003; Lee et al, 2012; Park et al, 2015; Raza et al, 2016; Tahir et al, 2017). Bacteria having potential growth-promoting activity include species of Pseudomonas, Bacillus, Stenotrophomonas, Serratia, and Arthrobacter (Ryu et al, 2003; Bailly and Weisskopf, 2012; Kai and Piechulla, 2014; Park et al, 2015; Raza et al, 2016). Park et al (2015) reported that 13-tetradecadien1-ol, 2-butanone, and 2-methyl-n-1-tridecene, produced by Pseudomonas fluorescens SS101, enhanced the growth of Nicotiana tabacum
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