Virulence Patterns of Puccinia recondita f. sp. tritici in Nebraska During 1992 and 1993. J. E. Watkins, Professor; Department of Agronomy, University of Nebraska, Lincoln 68583-0722. S. S. Rutledge, Research Technologist, Department of Plant Pathology, and P. S. Baenziger, Professor, Department of Agronomy, University of Nebraska, Lincoln 68583-0722. Plant Dis. 79:467-470. Accepted for publication 30 January 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-0467.

One hundred sixty-four urediniospore isolates of Puccinia recondita were collected in 1992 and 134 in 1993 from four wheat-growing regions in Nebraska. These were characterized for virulence to 16 near-isogenic, single-gene differentials in a Thatcher genetic background. Thirty-seven virulence combinations were identified from the isolates collected in 1992 and 46 were identified from those collected in 1993. Twenty-two new virulence phenotypes were de-tected in 1993 that were not found in 1992. Virulence was high during both years in all regions to LrI, Lr2a, Lr2c, Lr3, Lr10, Lr11, Lr18, Lr21, Lr24, and Lr30. The virulence frequency was moderate to Lr26, and was low to Lr3ka, Lr9, Lr16, Lrl7, and Lrl9 during both years. The most prevalent virulence phenotypes were TFH-10,18,21 (virulent on Lr1, Lr2a, Lr2c, Lr3, Lr24, Lr26, Lr11, Lr30, Lr10, Lr18, and Lr21) in 1992 and TFH-10,18 (virulent on Lr1, Lr2a, Lr2c, Lr3, Lr24, Lr26, Lr11, Lr30, Lr10, and Lr18) in 1993. Eighty-three percent of the 1992 isolates and 74% of the 1993 isolates had the Lr1, Lr2a, Lr2c, and Lr3 virulence phenotype. Virulence to resistance genes Lr3ka, Lr9, and Lrl6 was only detected in 1993. Lrl9 was resis-tant to all rust isolates collected both years. Combinations of these last four genes could pro-vide resistance to Nebraska's current leaf rust population.

Keyword(s): near-isogenic lines, wheat leaf rust