Physiological Races and Virulence Diversity of Puccinia graminis f. sp. tritici on Wheat in Ethiopia

Abstract

The physiologic races of the rust fungus Puccinia graminis f. sp. tritici in the main wheat-growing regions of Ethiopia were determined on seedlings of the standard wheat stem rust differentials following the international system of nomenclature. Forty-four races were identified among the 75 isolates studied over a period of four years. The 16 isolates collected in 2001 all belonged to different race groups. The 33 isolates collected in 2002 belonged to 23 race groups, and, the 17 and nine rust isolates collected in 2003 and 2004 respectively belonged to eight and three race groups. Most of the rust samples collected from individual wheat fields belonged to different groups with only a few belonging to the same race group. The physiologic race breakdown differed greatly from year to year. TTR was the only race identified in all cropping seasons. Races such as TTT, TTR, PTT, PTR and TTQ showed relatively wider virulence spectra. Races such as TTR and TTT showed a relatively wider spatial distribution. Generally, P. graminis populations in Ethiopia appear to be highly variable, and this should be an important consideration when devising a breeding programme for this country.