Rhizosphere bacterial communities associated with healthy and Heterodera glycines-infected soybean roots

• Rhizosphere bacterial communities of healthy and SCN-infected soybean plants were different.
• Occurrence of SCN disease was related to soybean rhizosphere bacterial community structure.
• Rhizosphere bacterial community structure of SCN-infected plants was affected by the biocontrol agent Purpureocillium lilacinus.

Bacterial communities in rhizosphere soil of soybean plants that were healthy, infected with soybean cyst nematode (SCN, Heterodera glycines), and infected with SCN but treated with Purpureocillium lilacinus YES-2 were investigated with community-level physiological profile (Biolog) and 16S rDNA clone library analyses. Biolog data indicated significant differences in substrate utilization patterns of the rhizosphere bacterial communities associated with healthy, SCN-infected, and SCN-infected plus P. lilacinus-treated plants; among the three treatments, substrate richness and catabolic diversity were lowest in the rhizosphere of healthy soybeans. Analysis of 16S rDNA profiles placed the soybean rhizosphere bacteria into seven groups: Proteobacteria, Actinobacteria, Acidobacteria, Firmicutes, Bacteroidetes, Chloroflexi, and an unclassified bacterial clade. The percentages of Rhizobiales and Actinobacteria clones were greater in the rhizosphere of healthy plants than SCN-infected plants, while the opposite was true for the proportions of Bacteroidetes and Firmicutes clones. Addition of P. lilacinus did significantly affect the rhizosphere bacterial community of SCN-infected plants. These results suggest that rhizosphere bacterial community may play an important role in the changes of soybean rhizosphere biological conditions during the infection process. Further studies will identify more specific changes in the rhizosphere bacterial community during the establishment and progression of SCN disease, and relate these changes to potential effects on disease management, soybean health, and soybean productivity.