A significant proportion of global wheat germplasm and 25% of the world‘s wheat area are potentially at risk from the wheat stem rust pathogen (one ill-famed race is Ug99). Researchers around the world are actively developing new wheat varieties/lines with adequate and durable resistance to rust pathogens. Until recently, durum wheat varieties in Ethiopia were released for production without information on resistance genes against stem rust.
The first part of this research focuses on identification of quantitative trait loci (QTLs, an early step in identifying and sequencing the actual genes underlying trait variation) that confer resistance to stem rust races of Puccinia graminis f. sp. tritici (Pgt) found in Ethiopia (including Ug99) using 95 recombinant inbred lines (RILs) developed from two durum wheat varieties ‘Kristal’ × ‘Sebatel’. RILs were evaluated for field resistance over a three year period and genotyped by microsatellite markers. Using composite interval mapping, nine QTL regions conferring resistance to stem rust (Sr) were identified on eight chromosomes. Several of the detected chromosomal regions did not possess previously characterised Sr genes. After further characterisation and successful validation, the markers linked to these newly identified QTL will be useful for breeding Pgt resistant wheat varieties.
The findings offer important perspectives for the transfer of stem rust resistance to new varieties by Marker Assisted Selection (MAS), as three or more loci from ‘Sebatel’ variety confers nearly complete and durable resistance to stem rust. ‘Sebatel’ has good yield performance and high grain quality; it could be used as a donor variety to transfer stem rust resistance to new genotypes. The second stage of the research aims to identify and measure stem rust resistance genes, based on linked molecular markers, in 22 durum wheat varieties released in Ethiopia during the period 1966 – 2009. The results provided preliminary indications of a low diversity in resistance genes of the released varieties.
The results of these studies provide useful information particularly for Ethiopian wheat breeders. They have been presented at various workshops and conferences and published in scientific journals and newsletters.