Bacilli are commonly used as plant growth-promoting agents but can be limited in effectiveness to certain crop and soil environments. The objectives of this study were to (1) identify
Bacillusstrains that can be consistent in promoting the growth of corn, wheat, and soybean and (2) determine whether physiological traits expressed in vitrocan be predictive of growth promotion efficacy/consistency and be used for selecting effective strains. Twelve Bacillusstrains isolated from wheat rhizospheres were evaluated in greenhouse pot tests with nonsterile soil for their effects on the growth of corn, soybean, and wheat. The strains also were assessed in vitrofor multiple physiological traits. All 12 strains increased corn growth significantly compared to the controls. The four most efficacious strains on corn Bacillus megateriumR181, B. safensisR173, B. simplexR180, and Paenibacillus graminisR200also increased the growth of soybean and wheat. No set of traits was a predictor of growth promotion efficacy. The number of traits expressed by a strain also was not an indicator of efficacy as strain R200 that was positive for only one trait showed high growth promotion efficacy. Effective strains can be identified through pot tests on multiple crop plants, but in vitrophysiological assays are unreliable for strain selection.