History of Bt
Japanese biologist, Shigetane Ishiwatari was investigating the cause of the sotto disease (sudden-collapse disease) that was killing large populations of silkworms when he first isolated the bacterium Bacillus thuringiensis (Bt) as the cause of the disease in 1901.
Ernst Berliner isolated a bacteria that had killed a Mediterranean flour moth in 1911, and rediscovered Bt. He named it Bacillus thuringiensis, after the German town Thuringia where the moth was found. Ishiwatari had named the bacterium Bacillus sotto in 1901 but the name was later ruled invalid. In 1915, Berliner reported the existance of a crystal within Bt, but the activity of this crystal was not discovered until much later.
Farmers started to use Bt as a pesticide in 1920. France soon started to make commericialized spore based formulations called Sporine in 1938. Sporine, at the time was used primarly to kill flour moths.
More products containing Bt were marketed, but many of these products had limitations. Bt products such as sprays are rapidly washed away by rain, and degrade under the sun's UV rays. Also, there were many insects that are not susceptible to any of the limited number of Bt strains known at the time. All the Bt strains known at the time were toxic to lepidopteran (moth) larvae only. There were also some insects that live within the plant or underground where the Bt sprays could not reach. Since synthetic insecticides were readily avaliable and often very efficient in killing insects, Bt was not used widly.
In 1956, researchers, Hannay, Fitz-James and Angus found that the main insecticidal activity against lepidoteran (moth) insects was due to the parasporal crystal. With this discovery came increased interest in the crystal structure, biochemistry, and general mode of action of Bt. Research on Bt began in ernest.
In the US, Bt was used commercially starting in 1958. By 1961, Bt was registerd as a pesticide to the EPA.
Up until 1977, only thirteen Bt strains had been described. All thirteen subspecies were toxic only to certain species of lepidopteran larvae. In 1977 the first subspecies toxic to dipteran (flies) species was found, and the first discovery of strains toxic to species of coleopteran (beetles) followed in 1983.
In the 1980's use of Bt increased when insects became increasingly resistant to the synthetic insecticides and scientists and environmentalists became aware that the chemicals were harming the environment. Bt is organic and it affects specific insects and does not persist in the environment. Because of this, governments and private industries started to fund research on Bt.
Today, there are thousands of strains of Bt. Many of them have genes that encode unique toxic crystals in their DNA.
With the advancement in molecular biology, it soon became feasible to move the gene that encodes the toxic crystals into a plant. The first genetically engineered plant, corn, was registered with the EPA in 1995. Today, GM (genetically modified) crops including, potato and cotton are planted throughout the world.