Wheat stem rust caused by Puccinia graminis f. sp. tritici is amongst the biotic factors which can cause up to 100% yield loss during epidemic years. The highland of Ethiopia is considered as a hot spot for the development of stem rust diversity. This study was carried out to analyze the virulence diversity of P. graminis f. sp. tritici and evaluate the seedling reaction of commonly grown wheat cultivars to selected virulent stem rust races. Race analysis was carried out by inoculating isolates on to the 20 differential hosts. A total of 20 races were identified from 32 isolates, which included the most prevalent races TTSNK, RRJJC, and HRJJC. Most of the the genes possessed by the differentials were ineffective against one or more of the tested isolates except Sr24. Three races (RRTTF, TTKSK and TTSNK) were used to determine the resistance ofeleven wheat cultivars at seedling stage in greenhouse. Three varieties (Tura, Shina and Kubsa) were susceptible to them, while all the three durum wheat cultivars were resistant. Thus, the use of Sr24 and SrTmp singlely or incombination with other genes through gene pyramiding has paramount importance as the additive effects of several genes offer the cultivar a wider base stem rust resistance.
Key words: Physiologic race, Puccinia graminis f. sp. tritici, Sr genes.
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