ORIGINAL PAPER Preparation and evaluation of Bacillus megaterium-alginate microcapsules for control of rice sheath blight disease R. Wiwattanapatapee • A. Chumthong • A. Pengnoo • M. Kanjanamaneesathian Received: 5 December 2012 / Accepted: 8 March 2013 / Published online: 19 March 2013 Ó Springer Science+Business Media Dordrecht 2013 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 sur- vival 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 temper- ature 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 bac- teria 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. Keywords Bacillus megaterium  Calcium alginate microcapsule  Biocontrol  Sheath blight disease of rice  Rhizoctonia solani  u.v. protection Introduction Rice sheath blight disease, caused by Rhizoctonia solani Ku ¨hn, is one of the most destructive rice diseases world- wide (Ou 1985). In high-input and high-production envi- ronments, sheath blight disease accounts for between 6 and 10 % loss annually in both temperate and tropical regions of Asia (Savary et al. 2000). Control of rice sheath blight disease has included the use of chemical fungicides (Chin and Bhandhufalck 1990; Damicone et al. 1993), planting resistant rice varieties (Rush and Lee 1992), and the application of biological control agents (Mew and Rosales 1986; Vasantha Devi et al. 1989; Gnanamanickam and Mew 1990; Gnanamanickam et al. 1992). Research has been conducted to control sheath blight disease of rice by identifying preferred strains of microbial antagonists, optimizing the conditions for producing effective control agents on a commercial scale, formulating microbial antagonists for effective application, and by testing the products in pot and field settings. (Lewis 1991; Lumsden et al. 1995; Rabindran and Vidhyasekaran 1996; R. Wiwattanapatapee Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand A. Chumthong Department of Agricultural Technology, Faculty of Agricultural Technology, Songkhla Rajabhat University, Muang, Songkhla 90000, Thailand A. Pengnoo Department of Earth Sciences, Faculty of Natural Resources, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand M. Kanjanamaneesathian (&) Faculty of Animal Science and Agricultural Technology, Silpakorn University, Phetchaburi IT Campus, Cha-Am, Phetchaburi 76120, Thailand e-mail: kmana@su.ac.th 123 World J Microbiol Biotechnol (2013) 29:1487–1497 DOI 10.1007/s11274-013-1314-4