Development of a Biological Seed Treatment for Bacterial Diseases

Bacteria can cause important plant and seedling diseases, which are challenging to control due to a lack of effective bactericides. One potential biological bactericide are bacteriophages, which have been shown to control plant pathogenic bacteria in foliar applications and when directly coated on seeds. In order for bacteriophages to be used as a seed treatment they must have compatibility with current seed coating polymers. Seed coating polymers are not only used for adhesion to the seed, but they can also help stabilize the biologic seed treatment. For this study the objectives were to test the compatibility of Clavibacter michiganense subsp. nebraskense bacteriophages with common seed treatment polymers in liquid suspension and when treated on maize (Zea mays subsp. Mays) seeds, assess shelf-life of seed treatment mixtures containing bacteriophages for multiple weeks, and determine if the treatments had an effect on germination. Bacteriophages were mixed with polymers and stored in a liquid form. From the results of the liquid storage study, compatible polymers were selected for on seed storage in which common stabilizers, skim milk and sucrose, were added to the polymer-bacteriophage mixture before drying on the seed. The mixtures dried in two hours after coated on seeds and the number of active bacteriophage was unchanged. The bacteriophages remained active on coated dry seeds and had a shelf-life for at least two weeks at the lower storage temperature. The addition of stabilizers increased the stability of active bacteriophages and solubility of the polymer coating, making the bacteriophages more available. These bacteriophage seed coatings have the potential to neutralize Clavibacter michiganense subsp. nebraskense, before they cause Goss’s wilt.