Seedling and Adult Plant Resistance in the Ethiopian Bread Wheat Landraces to Stripe Rust Disease

High yielding farmers’ bread wheat cultivars are threatened by emerging race(s) of stripe (yellow) rust caused by Puccinia striiformis f.sp. tritici (Pst) in the highlands of Ethiopia. In depletion of rust resistance in commercial cultivars, researchers often look for new sources from close relatives and landraces. The objective of this study was to determine stripe rust resistance in selected Ethiopian bread wheat landraces obtained from the Ethiopian Institute of Biodiversity (IBCE). In 2017, a total of 152 accessions were exposed to the prevailing stripe rust races in hot spot areas (Kulumsa and Meraro) in Arsi zone of Oromia region. In the second year (2018), only promising landraces (57) were evaluated both at seedling and adult plant growth stages. The seedling test was conducted in the greenhouse at Kulumsa research center using three (PstS2 (v32), (PstS11) and (PstS11 v25) Pst races. In field evaluations, terminal severity (TRS), coefficient of infection (CI), area under disease progress curve (AUDPC), disease progress rate (DPR) and head infection (HI) were considred. High disease pressure was noted with 100% severity on susceptible entries at both locations and seasons. Highly significant (P<0.001) differences were noted among the landraces for all disease parameters indicated above. Of the 152 landraces, 57(38%) exhibited lower or equal disease reaction compared to the resistant check(Enkoy) across locations. Overall, 18 accessions showed resistance to the prevailing Pst races both at seedling stage and field conditions whereas14 exhibited susceptible /intermediate reaction at seedling stage, but had lower disease reaction under field conditions. This study has identified potential sources of overall and adult plant resistance in the Ethiopian bread wheat landraces to the prevailing Pst races. The authors recommend further studies to determine the diversity and/or novelity of resistance genes in selected accessions. Future wheat improvement should focus on utilization of these genetic resources to minimize the re-current outbreak of rust diseases.