Resistance to TTKSK and TTTSK Races of Puccinia graminis f.sp. tritici in Ethiopian Tetraploid Wheat Accessions

Abstract

Ethiopia is the leading wheat producing country in East Africa. East Africa is a known hotspot for the evolution of new rust races of wheat. A case in point could be the evolution of a new race of stem rust called Ug99 that overcame the resistance deployed in wheat breeding for stem rust for many decades. Tetraploid wheat is an excellent source of stem rust resistance. In Ethiopia recent race analysis works showed that races TTKSK and TTTSK are the two dominant races distributed in major wheat producing areas of the country such as Arsi and Bale. Taking this into account, searching for sources of stem rust resistance to races TTKSK and TTTSK is an important breeding strategy. Therefore, this study was conducted to identify sources of resistance to the two major stem rust races from tetraploid wheat accessions. A total of 40 tetraploid wheat accessions comprising Triticcum durum, T. diccoccum and T. turgidum were evaluated both at the seedling stage at Kulumssa and adult plant growth stages at Arsi Robe under natural epidemics. In the seedling stage, most of the accessions were resistant to both races. The infection type range from ; to 2⁺. 2⁺ is the maximum infection type that was displayed by few of the accessions. All the tetraploid accessions displayed low infection types to both races. Stem rust occurred at epidemic level at Arsi Robe compared to other testing locations. Almost half of the accessions were completely susceptible to stem rust infection in the field condition. Five accessions exhibited a completely immune reaction to the prevailing races. The rest displayed a trace level of moderately susceptible reaction. Those accession that combined seedling and adult plant resistance to stem rust infection could be utilized in the durum wheat breeding program of Ethiopia.  

Keywords: Accessions, infection type, tetraploid, race, TTKSK, TTTSK.