| Popis: |
Multi-functional plant growth promoting rhizobacteria Bacillus subtilis AH18 and Bacillus licheniformis K11 have been shown to display synergic effects in promoting the growth of red peppers and in suppressing phytophtora blight and have a competitive relationship in a limited nutritional environment. In the present study, a powder formulation method using a commercially cheap and easily obtainable carrier was developed to formulate these excellent antagonistic Bacillus species into a product. When the endospores of both strains were simultaneously formulated using a synthetic zeolite of NaY and natural zeolite, the growth rate of the vegetative form of B. sublitis AH18 was 5×109 CFU/mL. In contrast, the growth of B. licheniformis K11 was suppressed when this formulation was used. However, when the synthetic zeolite of NaA was used in the simultaneous formulation, the survival rates of both bacteria at 45°C for 60 days was sustained and the bacterial concentration was the same as the initial injection concentration of 5×109 CFU/mL. Furthermore, when the growth rates of the liquid state endospore preparations at different pH values were examined for 60 days, the concentration of both the Bacillus species were shown to slowly decrease at pH 5.0 and pH 9.0, but under strong basic conditions (pH 11.0), both the bacteria maintained stable endospore counts. When the effects of the prototype formulated using the NaA carrier at pH 11.0 was investigated in in vivo pot tests, the formulation was shown to completely suppress the phytophtora blight and have an excellent growth promoting effect. Both the Bacillus species colonized the rhizosphere of red peppers for 15 days with more than 108 CFU/g. Therefore, the carrier formulation method developed in the present study using Bacillus endospores will allow for long storage of the product and can eliminate the competitive relationship between the two Bacillus species. In addition, if the formulation is commercially applied, several antagonistic microorganisms can be formulated into a single product, which is expected to be convenient for the manufacturing processes as well as increase the stability of the biological control agents for use in farmhouses. |
