Stem rust seedling resistance genes in Ethiopian wheat cultivars and breeding lines.
Stem rust caused by Puccinia graminis f. sp. tritici is one of the major biotic limiting factors for wheat production in Ethiopia. Host plant resistance is the best option to manage stem rust from its economic and environmental points of view. Wheat cultivars are released for production without carrying race specific tests against stem rust. Hence, genes responsible for resistance in commercial wheat cultivars are not known. The objective of this study was to postulate stem rust resistance genes present in Ethiopian commercial wheat cultivars and advanced breeding lines. Thirty durum wheat (19 commercial cultivars and 11 breeding lines) and 30 bread wheat (20 commercial cultivars and 10 breeding lines) were tested for gene postulation. Stem rust infection types produced on wheat cultivars and breeding lines by ten Pgt races was compared with infection types produced on 40 near isogenic lines carrying single stem rust resistance genes. A total of 11 stem rust resistance genes (Sr5, Sr7a, Sr7b, Sr8a, Sr9e, Sr11, Sr21, Sr27, Sr29, Sr30 and Sr37) were postulated to be present either singly or in combination in the durum and wheat cultivars and breeding lines. Except Sr30, the other postulated genes were susceptible to most of the prevalent Puccinia graminis f. sp. tritici races in Ethiopia. Since Sr30 is also ineffective against Ug99, a gene management strategy that incorporates a combination of genes (gene pyramiding) that provide sufficient protection should be devised to achieve a durable control of stem rust. In addition, the significance of Sr27, Sr29 and Sr37 has to be investigated for Ethiopian agriculture.
Key Words: Durum wheat, isogenic lines, Puccinia graminis