VIRULENCE PHENOTYPES OF PUCCINIA-RECONDITA F SP TRITICI IN URUGUAY

Samples of wheat leaves infected with leaf rust, caused by Puccinia recondita f. sp, tritici, were collected in Uruguay in 1989, 1991, 1992, and 1993. The leaf rust collections were processed and evaluated for identification of virulence phenotypes on Thatcher wheat Lines near-isogenic for leaf rust resistance genes. During the 4 yr, 37 virulence phenotypes were identified from a total of 316 single-uredinium isolates. The largest number of phenotypes were identified in 1989 when rust samples were collected from the near-isogenic lines. Rust collections from 1991-1993 were collected from local breeding lines and cultivars and were less diverse for virulence phenotypes. Virulence frequencies were very low or were not detected to lines with resistance genes Lr9, Lr16, Lr19, Lr21, Lr24, Lr25, Lr29, and Lr32. Phenotypes with virulence to Lr26 increased in frequency from 1989 to 1993. Certain virulence phenotypes of P.r. tritici in Uruguay were distinct from those reported in North America.