Population behaviour of predominant and virulent pathotypes of Puccinia triticina causing wheat brown rust in India

Population behaviour of two sets of pathotypes (77-5, 77-9, 104-2, 104-2; 77-5, 77-9, 104-2) of Puccinia triticina was studied in relation to wheat cultivars DBW71, DBW90, HD3086, HPW349, K1006, Local Wheat Hango (LWH), MP3336, PBW343, WH1124 and Agra Local at two temperature regimes under controlled greenhouse conditions. These wheat cvs belonged to different areas and were susceptible to all the pathotypes used in the studies. Predominance of a pathotype was the outcome of temperature, wheat variety and competition among the pathotypes. Both pathotype 77-9 and 104-2 were equally dominant in a population of 77-5, 77-9, 104-2 and 104-3. Pathotype 77-5 was less frequent. In a set of three pathotypes 77-5 was more frequent followed by 104-2 whereas 77-9 was nearly eliminated. Among the pathotypes used in the studies, 104-2 was the simplest and it emerged dominant on Agra Local and some other wheat cultivars. In fitness studies, pathotype 77-9 was found to possess less incubation period, latent period, produced more uredinio-pustules and urediniospores/cm 2 as compared to other pathotypes. It is indicative of the fact that the pathotype 77-9 followed by 104-2 is more competitive and fit in population and can overtake other pathotypes in the years to come.