Distribution of Bacillus thuringiensis Serotypes in Ehime Prefecture : Japan

Silkworm litters from 98 sericultural farms in Ehime Prefecture, Japan, were examined and 146 crystalliferous sporeformers were isolated from 18 farms. These isolates proved to belong to Bacillus thuringiensis serotypes 3a, 4a : 4b, 4a : 4c, 5a : 5c, 7, 8, and 10. Serotypes 4a : 4b, 4a : 4c, 7, and 10 were distributed predominantly. Most of the isolates produced typical rhomboidal parasporal inclusions and showed toxicity to the silkworm larvae, Bombyx mori. On the contrary, an isolate belonging to serotype 5a : 5c and 3 isolates belonging to serotype 10 produced unusual parasporal inclusions. They did not show any toxicity to the silkworm larvae.