Assessment of Ethiopian Wheat Lines for Slow Rusting Resistance to Stem Rust of Wheat Caused by Puccinia graminis f.sp tritici

The emergence and rapid spread of virulent races of wheat stem rust has driven a search for sources of resistance for durable resistance breeding. This study was carried out to identify possible sources of stem rust resistance between Ethiopian wheat lines. Two hundred and fifty-two wheat accessions and a universal suscept, cultivar Morocco were evaluated for their resistance at the seedling stage to the stem rust isolate Ug99 in a controlled environment. Ninety-one lines that exhibited intermediate and susceptible seedling reactions were further field tested in 2012 main season for their slow rusting characteristics. Among the 91, 38 genotypes that had high to moderate level of slow rusting were advanced to a 2013 off season field evaluation. Slow rusting resistance at the adult-plant stage was assessed through the determination of final disease severity (FRS), coefficient of infection (CI), and relative area under disease progressive curve (rAUDPC). The results revealed that wheat lines H04-2, 204408-3, 214551-1, 231545-1, 7041-1, 7514-1, 226385-1, 226815-1, 7579-1 and 222495-1 had low values of FRS, CI and rAUDPC and were regarded as good slow rusting lines. Of these 231545-1, 7041-1, 226815-1 and 7579-1 exhibited complete susceptibility at the seedling stage, with infection types ranging from 3- to 3+, which suggests that they possess true slow rusting resistance. Lines 237886-1, 227059-1, 203763-1, 226275-1, 227068-2, 226278-1 and 7994-1 had moderate values for the stem rust resistance parameters and were identified as possessing a moderate level of slow rusting. High correlations were observed between different parameters of slow rusting. Among the slow rusting lines 231545-1, H04-2 and 222495-1 had high yields and kernel weight in both seasons. The slow rusting lines identified from this study can be used to breed for stem rust resistance in wheat.