Dynamics of Stem Rust Population in India During 1966–1980 and Strategy for its Management

Fifteen years survey data of Puccinia graminis f. sp. tritici virulence reveals that the agroclimatic conditions in the Himalayas do not favour evolution of new races or biotypes while the Nilgiri and Palney hills of South India, the main foci, does. The identification of variants 11A, 24A, 40A, 40A-1 and 117A-I during last 15 years show that evolution of races in the southern hills and adjoining area occur every3-4 years and the races with many virulence factors dominate. In India, where sexual cycle is not functional, new biotypes were produced due to mutation and para sexuality among existing races. We substantiate the view that cultivation of a limited number of improved genotypes has led to the reduction in the race spectrum and dominance of a few races. Based on the present study it is suggested that simple varieties with a few vartical resistance genes in cyclic shifts or horizontally resistant varieties should be grown in the Nilgiri and Palney hills. Multilines and gene combinations should be deployed in various agroclimatic zones along the Puceinia path especially in Central and Peninsular India.