2-Phenylethylisothiocyanate concentration and bacterial community composition in the rhizosphere of field-grown...

Field experiments with two spring and two winter canola cultivars were conducted in two successive years to study the release of 2-phenylethylisothiocyanate (PEITC) by living canola roots during plant development. The PEITC concentration in the rhizosphere of living roots ranged between 0 and 12 119 pmol g^-1. Higher PEITC concentrations were detected in the first year in both spring and winter canola compared to the second year suggesting a strong impact of growth conditions on PEITC release. The PEITC concentration in the rhizosphere changed with plant development. In spring canola the PEITC concentration was highest at flowering. In winter canola the highest PEITC concentrations were found in autumn and in spring at booting. There were no differences in PEITC concentration in the rhizosphere between cultivars with high and low seed (winter canola) or root (spring canola) glucosinolate concentration. The rhizosphere bacterial community composition determined by denaturing gradient gel electrophoresis (DGGE) changed significantly with time. Some of the changes in bacterial rhizosphere community composition were correlated with the PEITC concentration in the rhizosphere. Other environmental factors such as plant dry matter and soil moisture also were significantly correlated with the bacterial community composition in the rhizosphere. It is concluded that PEITC can be released in sufficient amounts into the rhizosphere of living canola roots to be a selective factor for the bacterial community.