Bacterial communities within the rhizosphere and roots of vetiver (Chrysopogon zizanioides (L.) Roberty) sampled at different growth stages

Vetiver is a plant of Poaceae family known for its ability to produce essential oil in the roots which is especially used in the perfume industry. The composition and the amount of essential oil produced may vary depending on the microbial community associated with vetiver roots. This study aimed to evaluate the structure of total and diazotrophic bacterial communities inside the roots and in the rhizosphere of vetiver RAROS genotype at five plant growth stages by molecular methods (PCR-DGGE and sequencing). The predominant bacterial community varied depending on plant age (mainly in the roots) and origin (bulk soil, rhizosphere soil and roots). Sequencing of DGGE bands (16S rRNA) demonstrated that the most dominant group associated with vetiver RAROS genotype was affiliated with Gammaproteobacteria (65.4% of the sequences). The diazotrophic population varied with early root growth, being more stable after the third month of plant growth, and seemed to be more influenced by root exudates than the total bacterial community. Alphaproteobacteria class was dominant among the nifH-harboring population (58.3% of the sequences analyzed). This study provides important information for the isolation and selection of strains that may promote the vetiver RAROS genotype growth and, consequently, improve the essential oil production. (C) 2011 Elsevier Masson SAS. All rights reserved.