Preparation and evaluation of Bacillus megaterium-alginate microcapsules for control of rice sheath blight disease

Abstract

Bacillus megaterium encapsulated in calcium alginate microcapsules was prepared and tested for its efficacy against sheath blight disease of rice. In laboratory conditions, the aqueous suspension (1:100, v/v in potato dextrose agar) of the bacterial microcapsules (10(10) spores/ml) inhibited mycelial growth of Rhizoctonia solani (>99 %) after the microcapsules were produced and stored for 12 months at room temperature (28 ± 2 °C). The survival of the bacterium in the microcapsules in response to ultraviolet (u.v.) irradiation and high temperature was investigated. The survivability of the bacterium in the encapsulated form was greater than that of the fresh cells when it was subjected to u.v. (20-W General electric u.v. lamp from a 25 cm distance for 48 h) and a high temperature treatment (80 °C for 48 h). Cells of the bacterium were detected by scanning electron microscope on both the leaf sheath and the leaf blade (in pot tests in a greenhouse) after spraying encapsulated product. The number of bacteria on the surface of both rice tissues (5 Log. number/g of plant) after spraying with encapsulated product was not significantly different from that after spraying with fresh cells onto the rice seedlings. Spraying the encapsulated B. megaterium on rice plants in the greenhouse was as effective as spraying a chemical fungicide for suppressing rice sheath blight disease.

Dry flowable formulations of antagonistic Bacillus subtilis strain T429 by spray drying to control rice blast disease

“…These facts have stimulated researches on environmental-friendly strategies to control rice blast, such as applying biological control agents and discovering new pesticide formulations. Biological control of rice blast is a valuable alternative to the use of chemical pesticides, and many bacterial 3 formulations have been developed to combat rice blast in developing countries (Prabavathy et al, 2006;Krishnamurthy and Gnanamanickam, 1998;Armando et al,2007;Wiwattanapatapee et al,2013) . Bacillus subtilis can produce a broad array of antifungal lipopeptides, making this species a biological control agent (Ongena and Jacques, 2008 Dry flowable formulations contain inert ingredients, which prolong the shelf life and increase the efficacy of the products.…”

Efficacy of a simple liquid culture of <i>Bacillus megaterium</i> in suppressing grain discoloration disease of rice (<i>Oryza sativa</i>)

“…Various formulations of B. megaterium have been produced previously and their efficacy have been tested in a greenhouse and a small rice plot to control rice sheath blight disease (Kanjanamaneesathian et al 1998;Wiwattanapatapee et al 2004;Wiwattanapatapee et al 2007;Chumthong et al 2008;Wiwattanapatapee et al 2013;Chumthong et al 2016). Water-soluble granules of B. megaterium (Chumthong et al 2008) were also effective at controlling GD when sprayed in rice field trials (Kanjanamaneesathian et al 2009).…”

“…Bacillus megaterium was isolated from a watersoluble granule formulation (Chumthong et al 2008) that had been produced in February 2014 at the laboratory of the Faculty of Agricultural Technology, Songkhla Rajabhat University, Songkhla, Thailand. This bacterium was originally isolated from bulk soil in a paddy rice field, Satun province, Thailand (Kanjanamaneesathian et al 1998) and was used as an active ingredient in various formulations for controlling sheath blight disease (Pengnoo et al 2000;Wiwattanapatapee et al 2004;Wiwattanapatapee et al 2007;Chumthong et al 2008;Wiwattanapatapee et al 2013;Chumthong et al 2016). One gram of water-soluble granule was suspended in sterile water (9 mL) in a test tube and the mixture was vigorously agitated with a vortex.…”

Beneficial Bacillus Strains Improve Plant Resistance to Phytopathogens: A Review

“…In some formulations bacterial strains was included in organic fertilizer to fight against Fusarium [33]. In other formulations, Bacillus megatherium was included in alginate microcapsules [34], in pellets [35], or in formulations with effervescent systems, in order to release rapidly the bacteria [36]. The microbial preparation can be sometime used together with organic amendments to improve soil in semiarid areas [37].…”