FACTORS ASSOCIATED WITH DEVELOPMENT AND SPREAD OF KARNAL BUNT OF WHEAT (TRITICUM-AESTIVUM) IN NORTH-WESTERN INDIA

Post-harvest survey during 1986-94 revealed fluctuation in the inciden ce of karnal bunt [Neovassia indica (Mitra) Mundkur] of wheat (Triticu m aestivum L. emend Fiori & Paol.). The incidence was relatively high in wheat harvests of 1986, 1987, 1990 and 1991, viz 33.4, 24.7, 21.2 a nd 15.8% in the infected grain samples respectively. Congenial tempera ture (maximum 20.1 24.6 degrees C, minimum 5.9 12.1 degrees C) and rel ative humidity of 81.2-96.3% with frequent rains at anthesis stage of the crop favoured high incidence of the disease. The susceptible varie ties 'WL 711' and 'HD 2009' produced larger soli compared with toleran t 'WL 1562', `HD 2329' and 'WH 147', contributing more inoculum to the soil. Resultantly, the severity of infection remained high in disease -prone areas. Replacement of susceptible varieties with tolerant 'WL 1 562', 'HD 2285', 'HD 2329' and 'WH 147', having small sori, decreased the inoculum.