Evaluation of bread wheat germplasm for adult plant resistance to stem rust using artificial inoculation

Wheat stem rust, caused by Puccinia graminis f.sp. tritici, is a major biotic threat to wheat (Triticum aestivum L.) in many wheat-producing countries worldwide, including Ethiopia. The pathogen is capable of continuously evolving new fungal races with high reproductive potential. It can be easily dispersed by wind over large geographic areas, allowing it to attack resistant varieties. Under optimal environmental conditions, it can cause epidemics leading to severe yield losses (up to 100%). A total of 91 germplasms, comprising 81 advanced bread wheat lines and 10 varieties, including the susceptible check Morocco, were planted using an augmented design. The experiment was conducted with artificial inoculation on spreaders to evaluate their slow rusting response against four virulent stem rust races viz. TTKTF, TKKTF, TTKTT, and TTTTF under field conditions at the Kulumsa Agricultural Research Center during the 2022-2023 offseason. Slow rusting resistance at the adult-plant stage was assessed by measuring the final rust severity (FRS) and the average coefficient of infection (ACI). Accordingly, 50 (61.7%) of the advanced lines and 6 (60%) of the released varieties namely Boru, Abay, Shaki, Kakaba, Deka, and Dursa exhibited low levels of FRS and ACI. In contrast, 31 (48.3%) of the advanced lines and 4 (40%) of the varieties showed high FRS and ACI values. The germplasms with low FRS and ACI values were considered to exhibit good slow rusting resistance and could be recommended for release into production and/or used in breeding programs aimed at achieving durable stem rust resistance in Ethiopia.