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Transfer of Field Resistance to Puccinia coronata from Avena sterilis to Cultivated Oats by Backcrossing. M. D. Simons, Agricultural Research Service, U.S. Department of Agriculture, Department of Plant Pathology, Iowa State University, Ames 50011; Phytopathology 75:314-317. Accepted for publication 28 September 1984. 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/Phyto-75-314.

Fourteen strains of Avena sterilis, all lacking seedling resistance to the crown rust fungus (Puccinia coronata), were selected to represent a wide range of field resistance to this pathogen. They were crossed and backcrossed once and twice with the susceptible oat cultivar Clinton. Lines derived from F1, BC1, and BC2 plants were selected for cultivated plant type and exposed to P. coronata in the F6 and F7 generations in replicated hill-planted plot trials. The effect of P. coronata was measured by dividing grain yield and mean seed weight values of rusted plots by corresponding values for the same lines in rust-free control plots. Yields in the rust-free plots showed a uniform, significant progression of improvement as degree of backcrossing to Clinton increased. Resistance to P. coronata, as measured by depression of grain yield and seed weight, decreased with degree of backcrossing. Averaged over the 14 parents, 80% of the lines from F1, 58% from BC1, and 30% from BC2 plants were significantly more resistant than Clinton in terms of reduction in seed weight. Lines combining the yield of Clinton with a significant improvement in resistance appeared in progeny from all parents of A. sterilis. Mean heritability values for resistance measured by reduction in grain yield and seed weight were 41 and 58%, respectively. There was only a weak relationship between grain yield and resistance.

Additional keywords: disease resistance, germ plasm enhancement, wild germ plasm.