Efficacy of Stb resistance genes and pathotype diversity in Zymoseptoria tritici from Ethiopia

Zymoseptoria tritici, the causal agent of Septoria tritici blotch (STB) in bread wheat (Triticum aestivum), leads to significant global yield losses. Resistance breeding is vital for managing STB, but there is limited information on Z. tritici infection behaviour in Ethiopia. This study examined the virulence variability of Z. tritici isolates from Ethiopia's Central Highlands and evaluated the effectiveness of known wheat STB-resistance genes. Eight wheat lines were tested against six Z. tritici isolates, showing significant differences (p < 0.0001) in necrotic leaf area (%NLA) and pycnidia coverage (%PC) among the tested Z. tritici isolates, wheat lines and their interactions. Wheat genotype TE9111 exhibited specific resistance to 50% of the isolates, while Taichung 29 showed no resistance. Isolate ZSE158 was the most aggressive, causing 61.4% PC and 54% NLA. The Ethiopian isolates displayed broad virulence against resistance genes, including Stb2 - Stb7. TE9111, carrying Stb11, showed resistance to 50% of isolates, making it a valuable source for resistance breeding against STB. This study identified highly virulent pathogen isolates useful for wheat germplasm screening for STB resistance and also key resistance source materials for use in wheat resistance breeding in Ethiopia.