Effect of Crown Rust on Protein and Groat Percentages of Oat Grain 1

Abstract

Lines of oats (Arena sativa L.) in breeding nurseries at Madison, Wis. ranged from highly resistant to highly susceptible to infection by crown rust (Puccinia coronata Cda.). The correlation between crown rust severity (as percentage of leaf area affected) and the protein percentage of the grain averaged −0.470 over a 3-year period. Forty oat lines at Ames, Iowa ranged from moderate to high in susceptibility, as measured by the relative reduction in yield and seed weight caused by crown rust. With extremely high levels of infection, these strains showed significant variation in response of protein and groat percentages to infection. A significant reduction in protein percentage occurred in one strain and significant increases in protein percentages occurred in five other strains. Overall, the effect of crown rust on protein percentage was negatively correlated with its effects on yield (r=−0.362) and seed weight (r=−0.421). The effects crown rust on protein and groat percentages of the different lines, as measured in diseased plots, were not significantly correlated with either the inherent yields or the inherent protein percentages of the lines in unrusted control plots. This suggests that selection in breeding programs for high yield and high protein percentage could be carried out readily in conjunction with selection for crown rust resistance. The heritabilities of the effects of crown rust on protein and groat percentages were 81 and 91%, respectively.