Author(s):

Paritosh Kumar and RC Rai

Abstract: Wheat (Triticum aestivum L.) is the world’s most important food crop, serve as the prime item in the diet of millions of people. Spot blotch caused by Bipolaris sorokiniana is a destructive disease of wheat (Triticum spp.) in warm and humid wheat growing regions of the world. The fungus has a worldwide distribution but as a pathogen it is the most aggressive under the conditions of high relative humidity and temperature associated with the low fertility of soils. The yield loss due to the disease is very significant especially in North Eastern Plains Zone (NEPZ) of India, Nepal Terai and North Western Bangladesh. Estimates of yield losses due to spot blotch were reported to vary from 15.5 to 19.6% and up to 100% under severe infection conditions. Early symptoms are characterized by small, dark brown lesions ranging 1 to 2 millimeter long without chlorotic margin. In susceptible varieties, these lesions can extend very quickly in oval to elongated blotches, light brown to dark brown in colour. They may reach several centimeters before coalescing and inducing the death of the leaf. The pathogen has morphological and molecular variations among the isolates. Ideal conditions for spot blotch development on the leaves are relative humidity of near 95 per cent with an average temperature in the coolest month above 17°C and long periods (more than 12 to 18 hours) of leafs wetness caused by rainfall, irrigation, fog or dew. Recently a number of genotypes have been identified as donors for improving host resistance. The best way to control spot blotch is through an integrated approach including varietal replacement, agronomic management and need based application of fungicides.

Pages: 326-331  |  1381 Views  505 Downloads

Download (438KB)