Determination of yellow rust (Puccinia striiformis f. sp. tritici) races in wheat grown in the Mediterranean and Aegean region

Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) is one of the most important disease of wheat. In this study, Pst isolates were collected from wheat growing areas of Aegean and Mediterranean regions of Turkey during 2018 and 2019 growing seasons. The aims of the study were to determine virulence patterns of the Pst isolates collected from both regions and understand the genetic variation of them using co-dominant SSR markers. Based on virulence analyses, most isolates were determined as virulent with various frequencies to the resistance genes Yr6 (100%), Yr9 (84%), Yr7 (78%), Yr1 (50%), Yr8 (50%), Yr43 (47%), YrSp (41%), Yr17 (38%), Yr27 (31%), Yr10 (25%), Yr24 (22%), Yr32 (22%), Yr44 (6%) and YrTr1 (6%), and clustered into 6 virulence groups (VGs). However none of these was virulent to Yr5 and Yr15. These were also clustered into 4 molecular groups (MGs) based on genotypic data, and while all MGs were located in the Aegean region, Mediterranean region had three MGs (MG1, MG2 and MG3). Additionally, analysis of molecular variance analysis showed that genetic variation between isolates was mostly within isolates, and among isolates within regions. Genetic variation within the isolates accounted for 52.20% (p= 0.001) and among the isolates within regions 33.13% (p= 0.001). However, genetic variation among regions was not statistically significant with 14.66% explained variation (p= 0.129). The results illustrated that both regions had more complex Pst structure according to virulence and genotypic data, and interregional migration was high. These data should be helpful in wheat breeding programs conducted for resistance to Pst and understanding for population structure and migration of the pathogen.