Evaluation of Biocontrol Activity of Rhizobacteria from Beta vulgaris against Heterodera schachtii.

One hundred fifty rhizobacteria isolated from roots of Swiss chard grown in a soil suppressive to the sugar beet cyst nematode, Heterodera schachtii, were tested for their influence on the nematode's ability to hatch and infect roots. Two screening systems were used that focused on the ability of bacteria to inhibit either nematode hatching or root infection. Most of the bacterial strains reduced hatching in vitro compared to the control, while with 5% of the strains there were 0% hatch. Seven percent of all strains significantly reduced second-stage juvenile (J2) infection of mustard roots raised in soil-less growth pouches. Eighteen strains from four genera (Bacillus, Pseudomonas, Variovorax, and Arthrobacter) were selected for greenhouse trials. In the greenhouse trials four bacterial strains, including two strains of Bacillus megaterium, reduced nematode infection of sugar beet when eggs were used as inoculum. Seven bacterial strains reduced nematode infection of sugar beet in one of two trials when plants were inoculated with J2. Most of the effective strains were Bacillus spp., primarily B. megaterium. Colonization of sugar beets roots by two B. megaterium strains was found to be stable over 30 days in the greenhouse.