A comparison of sole carbon source utilization patterns and phospholipid fatty acid profiles to detect changes in the root microflora of hydroponically grown crops

Sole carbon source utilization (SCSU) patterns and phospholipid fatty acid (PLFA) profiles were compared with respect to their potential to characteri ze root-inhabiting microbial communities of hydroponically grown crops. Swe et pepper (Capsicum annum cv. Evident), lettuce (Lactuca sativa cv. Grand R apids), and four different cultivars of tomato (Lycopersicon esculentum cvs . Gitana, Armada, Aromata, and Elin) were grown in 1-L black plastic beaker s placed in a cultivation chamber with artificial light. In addition to the harvest of the plants after 6 weeks, plants of one tomato cultivar, cv. Gi tana, were also harvested after 4 and 8 weeks. The cultivation in this stud y was performed twice. Principal component analysis was used to analyze the data. Both characterization methods had the ability to discriminate betwee n the root microflora of different plant species, cultivars, and one tomato cultivar at different ages. Differences in both SCSU patterns and PLFA pro files were larger between plant species than between cultivars, but for bot h methods the largest differences were between the two cultivations. Still, the differences between treatments were always due to differences in the s ame PLFAs in both cultivations. This was not the case for the SCSU patterns when different plant ages were studied. Furthermore, PLFA profiles showed less variation between replicates than did SCSU patterns. This larger varia tion observed among the SCSU data indicates that PLFA may be more useful to detect changes in the root microflora of hydroponically grown crops than t he SCSU technique.