Protein Yield and Its Relationship to Other Traits in Backcross Populations from an Arenas ativa ✕ A. sterilis Cross 1

Relationships of various traits to protein yield of oats were studied by using F 2 ‐derived lines in the F 3 populations from Bc 0 through Bc 5 of an interspecific oat cross Avena sativa ✕ A. sterilis . Mean heritabilities ranged from 64 to 68% for heading date and plant height, 45 to 51% for bundle weight, straw yield, grain yield, growth rate, grain number, and protein yield, and 36 to 42% for harvest index, unit straw weight, groat weight, protein percentage, and protein per groat. Protein percentage had high negative genotypic correlations with grain yield and harvest index and positive genotypic correlations with plant height and protein per groat. Protein yield had genotypic correlations above 0.80 with bundle weight, straw yield, grain yield, growth rate, unit straw weight, and grain number, but it had no correlation with heading date, groat weight, protein percentage, and protein per groat. Thus, grain yield was the primary determinant of variation in protein yield, and protein percentage was negatively associated with grain yield and had little effect on protein yield. Simulated selection experiments based on the line mean (selection intensity = 5%) showed that selection for protein yield via itself or via grain yield both caused ca. 26% improvement; whereas selection for protein yield via protein percentage caused no improvement. Protein yield was significantly (P = 0.01)) above the recurrent parent in four oat lines. In three of these increased protein yield was primarily due to increased grain yield. The increased protein yield of the fourth line, however, was due 45% to increased grain yield, 46% to increased protein percentage and 9% to the interaction of these two traits.