Association of Host Cytoplasm with Reaction to Puccinia coronata in Progeny of Crosses Between Wild and Cultivated Oats. M. D. Simons, Research Plant Pathologist, ARS, U.S. Department of Agriculture, Department of Plant Pathology, Iowa State University, Ames 50011. L. D. Robertson, Vicia faba Breeder, International Center for Agricultural Research in the Dry Areas, Aleppo, Syria; and K. J. Frey, C. F. Curtiss Distinguished Professor in Agriculture, Department of Agronomy, Iowa State University, Ames 50011. Plant Dis. 69:969-971. Accepted for publication 8 April 1985. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1985. DOI: 10.1094/PD-69-969.

Five strains of Avena sterilis were crossed reciprocally with two A. sativa cultivars to give 20 hybrids. The 20 hybrids were backcrossed twice to their respective A. sativa parents, and 20 lines derived from each original cross were field-tested for quantitatively expressed resistance to artificially initiated epidemics of Puccinia coronata in the F₅ and F₆ generations. Controls were maintained free of rust with a fungicide, and resistance data were recorded as yield and seed-weight indexes obtained by dividing values in the diseased test plots by corresponding values in the control plots. Although the absolute differences were very small, populations derived from the cultivar CI 9170 showed significantly higher mean indexes in favor of the cultivated cytoplasm. Populations from the cultivar Otee showed a similar but nonsignificant mean trend. In a few individual crosses, A. sterilis cytoplasm was superior. Certain individual lines in each of the 20 populations had significantly greater resistance than their respective cultivated parents.