This application describes and claims a method of improving the health and vigor of a plant, comprising administering to the plant an effective amount of a bacterial composition which comprises a botanically compatible vehicle and an isolated bacterial strain selected from the group consisting of Bacillus megaterium PT6, Bacillus subtilis PT26A, Paenibacillus sp. ATY16, and any combination thereof. Improvement in health and vigor is one or more of the following: a) improved resistance to disease; b) improved ability to defend against disease; c) reduction of disease symptoms; d) faster growth; e) improved crop productivity; f) improved crop quality; g) improved seed germination; h) improved seedling emergence; or any combination thereof. Isolated bacterial strains and mixtures of bacteria are provided, as well as compositions comprising the isolated bacterial strains.