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Application of Restricted Selection Indexes for Improvement of Economic Value in Oats¹

The dollar return from growing oats Avena sativa L. in the midwestern United States is a function of both grain and straw yields. Restricted selection indexes were used to determine the effect of restricting heading date and height on selection potential for economic value among F₉-derived lines from a bulk populatiou of oats. Four unrestricted and eight restricted selection methods were considered. The eight restricted methods comprised two economic values, optimum and base methods, and two degrees of restriction on heading date and height. Expected and actual advances were calculated.

Direct selection for increased economic value saved lines with late heading dates and tall plants. Holding heading date and height to the means of the unselected population removed correlated responses in heading date and height, but decreased advance from selection for economic value. More severe restrictions on heading date and height reduced the advance in economic value to near 0.0. Restrictions on heading date and height had a more severe effect on straw yield than on grain yield.

Optimum restricted selection indexes, in which grain and straw yields were entered as separate traits, were only slightly more efficient than base restricted indexes in which the two traits were combined into the single character economic value.

Changing the relative economic values of grain and straw had little effect for economic value was effective with measurements on plant weight, heading date, and height only; i.e., without measuring grain yield.

Expected and actual advances for heading date and height agreed closely for all methods. Expected advances for grain yield, straw yield, and economic value were overestimates of actual advances with unrestricted methods, but agreed closely with actual advances for restricted methods.

Key Words: Grain yield • Straw yield • Plant weight • Heading date • Height

² Plant breeder, Dep. of Agriculture, Western Australia (formerly graduate student of Iowa State Univ., Ames, Iowa), Population geneticist, Plant Physiology Division, DSIR, Palmerston North, New Zealand (formerly graduate research assistant, Iowa State Univ., Ames, Iowa), and professor of agriculture, respectively.

Received for publication February 6, 1976.