First report of race TTRTF of wheat stem rust (Puccinia graminis f.sp. tritici) in Eritrea.
Race TTRTF of Puccinia graminis f.sp. tritici was first detected in 2016 in a severe outbreak of wheat stem rust on thousands of hectares of durum and bread wheat in Sicily, Italy. However, a recent study suggested that TTRTF was already present in Georgia in 2014. During 2016-18, some 140 samples of rust-infected wheat and barley were collected from field trials and farmers' fields in Eritrea and submitted to the Global Rust Reference Center (GRRC), Denmark. Fifty-one urediniospore isolates were derived from 62 samples recovered on the susceptible wheat cultivars Morocco and Line E. Race typing was completed for 40 isolates based on 20 North American wheat lines using the standard race-typing procedures and infection type (IT) criteria determining virulence and avirulence. All isolates except two, representing 24 sampling sites, were diagnosed as TTRTF, whereas two samples collected from farmers' fields in Metera and Temajila were identified as TKKTF and TTKSK, respectively. In April 2019, two stem rust samples were collected from wheat in Fars province, Iran. After submission to GRRC, two single-pustule isolates per sample were raised and race typed as described above. All isolates were determined to be race TTRTF, previously reported without data documentation. This is thought to be the first report of race TTRTF in Eritrea (2016) and southern Iran (2019). TTRTF had virulence for 23 Sr genes (IT 3 or higher): Sr5, Sr6, Sr7a, Sr7b, Sr8a, Sr9a, Sr9b, Sr9d, Sr9e, Sr9g, Sr10, Sr11, Sr13b, Sr17, Sr21, Sr35, Sr36, Sr37, Sr38, Sr44, Sr45, SrTmp and SrMcN. Fed*3/Gabo*51BL.1RS-1-1 (Sr50) showed IT 3-3, which is significantly higher than for typical avirulent isolates. Simple sequence repeat genotyping of TTRTF isolates confirmed that they belonged to clade III-B.