Multiple resistance genes to leaf and stem rust in Brazilian wheat varieties 'BRS194' and 'Toropi'

Leaf (Puccinia triticina; Pt) and stem (Puccinia graminis tritici; Pgt) rust are important constraints to wheat production. The leaf and stem rust resistance in the Brazilian wheat varieties 'Toropi' and 'BRS194' was evaluated using a 'Toropi/BRS194' doubled-haploid (DH) population. Parents evaluated at the seedling stage with Pt race MCJ-HN displayed infection type (IT) = ;1 for 'BRS194' and IT = 3 for 'Toropi'. The DH progeny fit a 1R:1S ratio, indicating a single Lr gene in 'BRS194' was effective against race MCJ-HN. Adult plant testing with isolate 18-96-1 CCDS found that 'BRS194' displayed an IT = 3 and 'Toropi' IT = 1(-), with segregating progeny consistent for multigenic adult plant resistance in 'Toropi'. The parents and DH progeny were screened for the 1BL.1RS translocation (Sr31) with marker PE061, with 'Toropi' negative and 'BRS194' positive for the presence of Sr31. 'BRS194' was also tested against Pgt races MCCF, QTHJ, RHTS, RTHJ, TMRT, TPMK, and TTKSK at the seedling stage. BRS194 was resistant to all Pgt races, and an IT = 0 to TTKSK suggested the presence of Sr36. The presence of Sr36 in 'BRS194' was supported by the molecular marker STM773-2 (+) and 'Arthur 71' (Sr36 carrier) in its pedigree. Most resistant lines carried the Sr36-associated allele of STM773-2, while a few did not, indicating the presence of a second gene conferring resistance to TTKSK. Seedling resistance to Pgt in 'Toropi' was effective against races RHTS, MCCF, QTHJ, and RTHJ, postulated to be Sr9e. The variety 'BRS194' has effective rust-resistance genes that can be used in wheat-breeding programmes.