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Effect of Crown Rust on Oat Groat Protein. L. L. Singleton, Assistant professor, Department of Plant Pathology, Oklahoma State University, Stillwater 74074; D. D. Stuthman(2), and M. B. Moore(3). (2)Associate professor, Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul 55108; (3)Professor emeritus, Department of Plant Pathology, University of Minnesota, St. Paul 55108. Phytopathology 69:776-778. Accepted for publication 16 February 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-776.

Oat (Avena sativa L.) cultivars of differing susceptibility to crown rust were evaluated in the field in 1971 and 1972 to ascertain their percentage of groat protein (PGP) and total protein yield (TPY) with and without infection by Puccinia coronata f. sp. avenae. Without rust in both years, the 12 cultivars exhibited significant differences in both PGP and TPY. Crown rust epidemics were characterized as moderate in 1972 and severe in 1971, owing to differences in time of epidemic initiation at distinct plant growth stages. With rust, PGP and TPY for all cultivars decreased an average of 1.1% and 75 g per plot in 1971, compared with 0.4% and 20 g per plot in 1972, respectively. Thus, the greater epidemic severity in 1971 led to a larger average reduction in PGP and TPY than in 1972. However, the TPY and PGP responses of cultivars with rust varied more in 1972. In both years with rust, some cultivars (Coachman and Tippecanoe) were affected to a greater degree than Kota regardless of epidemic severity because of differences in their crown rust resistance. The data also suggest that cultivars with high PGP potential may respond more significantly to the effects of crown rust than cultivars with low PGP potential. The effects of crown rust on protein accumulation are most striking when measured in terms of TPY.