Karnal bunt: A minor disease that is now a threat to wheat

Abstract

Karnal bunt of wheat, caused byNeovossia indica (Mitra) Mundkur, was first reported in 1931 from Northwestern India in experimental plantings. For many years it was a minor disease found only in Northwestern India. During the 1969–70 crop season it was unusually widespread in Northwest India and since 1974–75 Karnal bunt has been distributed throughout Northern India from West Bengal to the western border. Seed lots with more than 50% of the kernels infected have been collected from farm threshing sites. The disease is now established in Afghanistan, Iraq, Pakistan and Mexico and has been intercepted in India in wheat seed that was shipped from Lebanon and Syria. The increased geographic distribution of Karnal bunt may be due to the development and wide distribution of wheat cultivars that were more susceptible than the older wheats that were grown in India prior to 1969–70. Resistance to Karnal bunt has been reported in several Indian wheats but most cultivars are susceptible. Hexachlorobenzene and cyano (methylmercuric) guanidine each prevented germination of teliospores ofN. indica in tests in Mexico.