PATTERNS OF POTENTIAL C SOURCE UTILIZATION BY RHIZOSPHERE COMMUNITIES

Patterns of potential C source utilization by microbial communities we re tested as a means for differentiating among and within rhizosphere samples of different crops. Utilization of 95 separate sole C sources was determined by inoculating microbial suspensions into BIOLOG plates and quantifying color production from a redox-sensitive dye. Suspensi ons were produced by shaking excised root samples from wheat, white po tato, soybean and sweetpotato grown in hydroponic culture within contr olled environmental growth chambers. Distinctive patterns of C source utilization were apparent for each crop type, and the differences amon g crops were consistent for experiments repeated over 2 years. A tempo ral shift in C source utilization related to plant development state w as observed in soybean. Results indicate that this rapid method is eff ective for detecting plant dependent differences in rhizosphere commun ities, and changes in response to plant developmental state.