*Corresponding author: aamiriqbal890@aup.edu.pk

This study involved 30 European (EU) wheat lines and encompassed multiple locations, spanning a total of 25 environments (location x year). The diversity of yellow rust disease resistance was also assessed using molecular markers (11 Yr markers). The study also assessed the existence of diverse and recombinant Yr (P. striiformis) pathogen genetic lineage on European (EU) wheat lines prevalent in the studied.

The results indicated a steady progression of the disease pressure across the scoring at locations during the study period. Considering the impact of different years, the disease incidence was highest in 2018 and lowest in 2022. For much of the EU wheat lines, the disease incidence ranged from 20% to 60% during the 2018-2019 seasons. In contrast, the overall disease incidence was very low, ranging from 0% to 20%, at all locations during the 2020-2021 season.

Among the tested EU wheat lines, none exhibited complete resistance across all tested locations (ACI=0). This suggests the presence of major gene-based resistance or possibly a combination of several minor genes, as opposed to partial resistance. The diversity of EU wheat lines based on molecular markers was evaluated using a set of 11 molecular markers linked to yellow rust (Yr) genes.

The analysis revealed that the Yr5 markers was the most common, detected in 89% of the EU wheat lines, followed by Yr34 (detected in 68%), and Yr6 (detected in 21%) of the tested EU wheat lines while none of the EU wheat lines showed the presence of Yr1, Yr7, Yr9, and Yr36. This highlights the presence and absence of diverse yellow rust disease resistance in EU wheat lines, making them a valuable resource for enhancing the resistance level in Pakistani (PK) germplasm.

The result also showed that the population was relatively divergent compared to PK germplasm. An overall selection was observed in the isolates collected from EU or PK germplasm whereas this impact was absent within the germplasm for wheat lines, which means that the overall germplasm had impact on the pathogen structure, but within each germplasm the wheat lines are equally infected by different pathogen lineages.

Additionally, different pathogen genetic lineages attacked the EU wheat lines and none of these EU wheat lines were attacked by a specific pathogen lineage across the locations.

This information on the response of EU wheat lines not only provides valuable insights for utilizing them as a source of novel resistance but also aids in predicting their performance against potential future invasive strains from the Himalayan region. The deployment of EU wheat lines and their crossing with PK germplasm would contribute strongly to reduce the disease burden on wheat under the Pakistani conditions.