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Comparison of Selection Efficiency for Grain Yield in Two Population Densities of Four Spring Wheat Crosses¹

Selection efficiency for high-yielding lines in four F2 populations of spring wheat (Triticum aestivum L.) was compared at two population densities based on plant head weight. The mean yield of F₄ lines selected on the basis of high head weight as F₂ plants was greater than that of lines with low head weight, with significant differences at the 5% level in a combined 2-year analysis. The mean yields of lines selected at high population densities were greater than those of lines selected at low population densities, irrespective of plant head weight in the F₂. Almost twice as many lines yielding in the top 15% in F₄ were selected in F₂ at high population densities than at low population densities. A considerably smaller number of high-yielding lines were from the lowyielding category in F₂. The results suggest that individual plant selection should be practiced at high population densities if the selected lines are to be subsequently evaluated at high population densities comparable to commercial seeding rates.

Key Words: Triticum aestivum L. • Plant head weight

² Research scientist, Research Station, Agriculture Canada, P. O. Box 1210, Charlottetown, Prince Edward Island C1A 7M8.

Received for publication March 22, 1977.