Herbivore feeding assay.

For the S. littoralis no-choice assay, 26-day-old A. thaliana plants received one neonate S. littoralis larva (provided by Syngenta AG, Switzerland). Cellophane bags were placed over the plants to prevent larvae from leaving the plants. Larvae were collected 6 days postinfestation, freeze-dried, and weighed to the nearest 0.001 mg on a microbalance (Mettler Toledo MT5, USA). As for the pathogen infection experiment, this experiment consisted of 13 treatments (12 bacterial strains and the noninoculated control) and 20 to 34 plants per treatment. Due to space constraints, the 12 bacterial strains were divided into two sets, each consisting of 6 bacterial strains and a noninoculated control. Plant numbers per treatment varied as a result of plants that were bolting or larvae that escaped, were potentially overlooked, or died during the experiment and were excluded.

A second repetition of this experiment was performed with a subset of the best candidate strains (Pseudomonas sp. P97-38, Pseudomonas orientalis L1-3-08, and Pseudomonas aridus R1-43-08) along with additional controls that were bagged with cellophane bags but not infested with S. littoralis (uninfested). The procedure followed the first experiment, but in addition to the weight of freeze-dried larvae, the fresh shoot weights of S. littoralis-infested and uninfested plants were recorded and the percentage of plant tissue removed was estimated by taking the fresh shoot weight of each damaged plant relative to the mean fresh weight of all uninfested plants of the respective treatment.