The genus Nicotiana includes more than 60 species, of which N. tabacum and N. rustica are the two commonly cultivated for producing commercial tobacco. N. tabacum is widely cultivated in most countries of the world while N. rustica is restricted to India, Russia and few other Asiatic countries. The primary centre of origin of N. tabacum is South America and that of N. rustica peru. In India, tobacco is grown when the mean temperature is 20° to 27°C. When grown as rainfed crop, it requires at least about 500 mm of well distributed rainfall during crop growing season.