Soil bacterium Bacillus subtilis (GB03) augments plant growth and volatile emissions in Eruca sativa (Arugula)



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Plant growth-promoting rhizobacteria (PGPR) are naturally occurring soil microorganisms that colonize roots to stimulate plant growth and development by increasing harvest yields, plant weight, seed germination, and resistance to abiotic stress. A commercially available bacterial strain Bacillus subtilis GB03 emits a complex blend of bacterial volatile organic compounds (VOCs) that promote plant growth in Arabidopsis. Here we address the question whether GB03 VOCs induce growth in the agricultural salad crop Eruca sativa (Arugula) and how flavor components are influenced by GB03 exposure. In vitro plant exposure to GB03 increased fresh and dry plant tissue weight compared to water treated controls. To analyze for flavor components, crushed Arugula plant tissue was analyzed for volatile emissions. Headspace odors were collected onto solid phase micro extraction (SPME) fibers and subsequently analyzed by gas chromatography (GC) flame ionization detection (FID) and/or mass spectroscopy (MS). Total plant volatile emissions increased in Arugula by ca. 3 fold with GB03 exposure for 21 days compared with the water treated controls. The 6 peaks with the largest areas as observed by GC–FID were identified as hexanal, nonanal, 4-pentenyl isothiocyanate, cis-3-hexenyl butanoate, cumin aldehyde, and 4-methylthiobutyl isothiocyanate. Since such sulfur components are associated with Arugula flavor, GB03–induction of these volatiles may well maintain flavor at the same time that GB03 induces plant growth.



Bacillus subtilis, Polyglycerol polyricinoleate (PGPR), Volatile organic compound (VOC), Eruca sativa, Arugula, Volatile emissions, Gas chromatography/flame ionization detector (GC-FID), Gas chromatography–mass spectrometry (GC-MS)