Virulence Specificity of the Puccinia graminis f. sp. tritici Population Originating from Durum Wheat in the Altai Region of Western Siberia, Russia

For the first time, a race survey of Puccinia graminis f. sp. tritici (Pgt) population was conducted on Triticum durum in the Altai region of Western Siberia, Russia. A total of 34 single-pustule isolates with different virulence phenotypes were identified on durum wheat (Triticum durum) in 2025 and compared with Pgt from bread wheat (Triticum aestivum). The UPGMA-based clustering separated Pgt isolates into two distinct groups, suggesting the host-driven differentiation that was further proven using population genetics tools. The pathogen isolates from durum showed a wider range of virulence complexity, higher variability, and greater average singularity. Virulence frequencies of Pgt on T. durum and T. aestivum differed markedly for Sr6, Sr7b, Sr9e, Sr17+13, and several other genes, while Sr24 and Sr31 remained effective independently of the pathogen origin. Two races, PKCSF and NFMSF, were detected on both the hosts, indicating a shared pathogen gene pool between bread and durum wheat. Even assuming host-specific divergence of Pgt in the Altai region, there is a need for the deployment of the same resistance genes into both T. aestivum and T. durum cultivars to prevent an outbreak of stem rust in the event of favorable conditions for inoculum exchange between crops.