Submitted to: Horticultural International Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2003
Publication Date: 1/15/2004
Citation: Kloepper, J., Reddy, M., Kenney, D., Burelle, N.K., Martinez-Ochoa, N., Vavrina, C. 2004. THEORY AND APPLICATION OF RHIZOBACTERIA FOR TRANSPLANT PRODUCTION AND YIELD ENHANCEMENT. Horticultural International Congress Proceedings. 631:219-229. Interpretive Summary: The goal of this project was to determine if a biological preparation consisting of combinations of bacterial strains could protect vegetable transplants against diseases for several weeks after transplanting into the field through accelerated plant development. Studies were designed to 1) increase the rate of seedling growth and decrease the time required to produce transplants in greenhouses, 2) develop disease-suppressive transplants that are protected from multiple diseases through combined mechanisms of stimulated plant defenses and increased activity of indigenous antagonistic microorganisms on plant roots, and 3) increase yields. Yield response to the combination treatment in tomato, pepper, and cucumber were significantly higher compared to controls in many repeated field trials across the United States. Recently Gustafson, LLC., has commercialized this preparation under the name "BioYield". BioYield is incorporated into the potting mix used to prepare transplants. Treated transplants demonstrate increased growth during greenhouse production. Upon transplanting to the field, treated seedlings exhibit less transplant shock and develop new roots more quickly. Disease protection is sometimes observed; however, the most reproducible effect is growth promotion resulting in yield increases with many transplanted crops.
Technical Abstract: PGPR (plant growth-promoting rhizobacteria) are root-colonizing bacteria that benefit plants by increasing plant growth or reducing disease. Biological disease control by PGPR is reported in many crop and pathogen combinations under experimental conditions. The level of disease control is typically less than that of fungicides or other chemical controls. Current applications of PGPR as biocontrol agents use mixtures of PGPR as components in integrated management systems that include reduced rates of agrochemicals and cultural control practices. A renewed interest in PGPR for practical application in agriculture and horticulture has resulted from the finding that some strains of PGPR can elicit systemic disease protection. This phenomenon is termed "induced systemic resistance" and is similar to systemic acquired resistance, which is elicited by pathogens and some chemical elicitors. According to the theoretical models of systemic resistance developed in laboratory and greenhouse experiments over the past two decades, treatment of plants with appropriate elicitors causes signal transduction in the plant that leads to activation of genes that encode various plant defense compounds. This response is seen phenotypically by reductions in the severity of diseases following inoculation with a wide range of pathogens, including bacteria, fungi, and viruses