Evaluating the potential effects of plant growth promoting rhizobacteria on the induction of volatile organic compounds (VOCs) in cotton

Plant growth promoting rhizobacteria (PGPR) represent a wide range of root-colonizing bacteria whose application is often associated with increased rates of plant growth, suppression of soil pathogens, and the induction of systemic resistance against insect pests. The effects of application of PGPR on induction of volatile organic compounds in treated plants have gone virtually unexamined, despite evidence that induction of plant volatiles is dependent on the interactions of biotic factors, such as herbivore-derived elicitors, and abiotic factors, such as wounding, and temperature. This study was conducted to evaluate the potential effects of PGPR on the induction of cotton volatiles. Three PGPR strains (INR-7, Blend 8, and Blend 9) were tested. PGPR strains were applied as spore preparations to cotton seeds. Cotton plants were then grown under green house conditions and headspace volatiles were collected from PGPR treated and untreated cotton plants 4-6 weeks post planting. Volatiles were analyzed and identified using gas chromatography-mass spectrometry. Noticeable quantitative differences in headspace volatiles were recorded between extracts from PGPR treated and untreated cotton plants. These results demonstrate that application of PGPR in cotton plants elicits changes in cotton plant volatile organic compounds and that these volatile changes may further influence chemical mediated tritrophic interactions.