ABSTRACT
328Spot blotch caused by a hemiobiotorphic fungus, Bipolaris sorokiniana is quite important disease of wheat in warmer and humid climate of South Asia and other parts of the world. It is the major cause of leaf blight in India. The disease is capable of causing yield losses up to 50% in susceptible varieties and also in seed viability as well as seed discolouration. The seed infected due to B. sorokiniana carries the infection besides crop residue, weeds, and soil. The disease affects the wheat crop from seed germination till seed development and causes symptoms on seed, seedlings, roots, leaves, leaf sheath, and spike. The infected leaves initially develop minute necrotic spot which may or may not be surrounded by yellow halo and presence of halo and its intensity depends on the level of resistance to spot blotch in wheat genotypes. The pathogen also produces “helminthosporol” toxin which is capable to produce necrotic symptoms. Although disease may be managed using fungicidal seed treatment and foliar sprays, but deployment of resistant cultivars remained the most popular method of disease management. During last two decades, research is carried out on pathogenic variability, creation of disease epiphytotics, rating scale, and unveiling the mechanism of host resistance in case of spot blotch. The chapter summarize the information on host resistance against spot blotch caused by B. sorokiniana.
