M. Kanjanamaneesathian

Spray-dried powder of Bacillus megaterium for control of rice sheath blight disease: Formulation protocol and efficacy testing in laboratory and greenhouse

A spray-dried powder containing Bacillus megaterium was developed and tested for control of rice sheath blight disease in the greenhouse. The formulation consisted of 20 ml of an endospore suspension of B. megaterium, 20% w/v of skim milk powder and 1.25% w/v of polyvinyl pyrrolidone k-90, that were mixed and spray dried at 120 °C. The powder displayed good physical characteristics, such as a low-moisture content and a high solubility in water. Bacterial viability in the powder was 3.5±0.1 × 1011 cfu/g after production and remained relatively stable (at 2.2±0.1 × 1010 cfu/g) after 12 months of storage at room temperature. In the laboratory, a 0.1% (w/v) aqueous solution of the formulation was effective in inhibiting the mycelia growth of Rhizoctonia solani (98.5±0.1% inhibition). Under greenhouse conditions, a 0.1% (w/v) aqueous solution applied by either spraying 1 day before inoculating R. solani or spraying 1, 7 and 15 days after inoculation of rice plants with R. solani was more effective in suppressing sheath blight disease than the blank formulation but was less effective than a chemical fungicide control.

Bacillus for Rice Cultivation in Thailand

Rice (Oryza sativa) is the most important cereal in the tropical region. It has been the main source of energy and nutrition for approximately 2.9 billion people. Because of its significance, rice has been subjected to a thorough scientific investigation. Internationally, the International Rice Research Institute (IRRI), based in the Philippines, has played a leading role in producing the improved rice varieties with better yield and resistance to insect pests and plant diseases. In Thailand, Rice Department, Department of Agriculture, and Department of Agricultural Extension have been responsible in conducting research and disseminating research outcomes (such as new rice varieties, knowledge in cultural practice for rice, and technology for controlling pests in rice) to the Thai rice farmers. The concern about both environmental deterioration as a result of overusing the chemical agents in rice production and health well-being of the farmers due to an exposure to toxic chemical agents has prompted the shift in the focus on researching in rice, and subsequent extension work conducted by various government agencies in Thailand. With the trend in sustainable production, natural-based products have been recommended to the farmers for use for both rice growth promotion and rice pest control. The natural-based products include crude botanical plant extract, wood vinegar, simple biomass of effective microorganisms (EM), biomass of antagonistic fungus Trichoderma harzianum growing on sterile cereal grains, and formulation of antagonistic Bacillus spp. Some of these natural-based products, such as biomass of EM, are recommended by the local agricultural officials and are commonly used by the farmers and their continual usage is a matter of trial and error. Formulations of antagonistic fungus and particularly antagonistic Bacillus spp. have been devised and have been subjected to rigorous laboratory, greenhouse, and field tests. Essential role of the stakeholders, such as local agricultural staffs, the farmers, and the researchers has been identified and highlighted as it will provide the model for further research and extension work in other rice growing areas.