Evaluation of Fava Bean for Resistance to Ascochyta fabae and Development of Host Differentials for Race Identification. K. Y. Rashid, Former Research Associate, Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2. C. C. Bernier, and R. L. Conner. Professor of Plant Pathology, and Former Research Associate, Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada R3T 2N2. Plant Dis. 75:852-855. Accepted for publication 11 March 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0852.

A total of 372 populations of fava bean (Vicia faba) were evaluated for resistance to Ascochyta fabae under field and growth room conditions. In the field, fava bean populations varied considerably in reaction to two isolates of A. fabae. After three cycles of testing and mass selection, the level of heterogeneity was reduced, but no population was homogeneous for resistance. A total of 18 and 11 populations were identified with >80% plants resistant to isolates A and Y¹, respectively, and two populations had >80% plants resistant to both isolates. The level of homogeneity was improved with continuous selfing in the growth room. After four cycles of testing and selfing, seven and eight inbred lines (S₄) were homogeneous for resistance to isolates A and Y¹, respectively, and five were homogeneous to both isolates. Eight inbred lines differentiated 10 isolates of A. fabae into seven races.