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Comparison of S₁ and Modified Ear-to-Row Recurrent Selection in Four Maize Populations. I. Effects on Population Means and Variances¹

Concern for the narrow genetic base of modern maize (Zea mays L.) hybrids has resulted in an increased interest in a population approach to germplasm improvement and the most effective recurrent selection methods for the adaptation and improvement of such populations. Two widely used procedures for intrapopulation improvement in maize are S₁ (S) and modified ear-to-row (ME) selection. The objective of this study was to compare the effectiveness of these two procedures in four open-pollinated maize populations, Afton (A), Schindelmeiser (S), Gelber Badischer Landmais (G), and Northwestern Dent (N). The primary trait of selection was performance index (PI = grain yield/percent grain moisture). The effects of selection were assessed for PI, the components of PI: grain yield and percent ear moisture at harvest, and other agronomic traits. Genetic variance was estimated to determine possible relationship to observed progress from selection. Data are reported for the initial three cycles of each selection procedure. The S selection for PI resulted in significant average linear increases in PI of 13, 12, and 19% per cycle in A, G, and N, respectively. Increases in PI were a result of increases in grain yield and decreases in percent moisture at harvest. ME selection produced no significant changes in PI. Genetic variances were estimated by subtracting environmental variance (as estimated from single-cross hybrids) from the phenotypic variance of each cycle. Significant reductions in genetic variances from Cycle 0 were detected for grain yield in (S)Cycle 3 of S, G, and N, and were numerically lower in all selected populations. Genetic variances for percent ear moisture declined significantly in only two instances, ^(ME)Cycle 3 and G(S)Cycle 3. This study indicated that S selection was the preferred method of intrapopulation improvement compared to ME selection.

Key Words: Corn • Genetic variance • Percent moisture • Yield • Performance index • Zea mays L.

² Assistant professor, Dep. of Horticultural Science and professor, Dep. of Crop Science, Univ. of Guelph, Ontario, Canada, NIG 2W1.

Received for publication August 19, 1986.

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				E.A. Lee, R. Chakravarty, B. Good, M.J. Ash, and L.W. Kannenberg Registration of 38 Maize (Zea mays L.) Breeding Populations Adapted to Short-Season Environments Crop Sci., November 21, 2006; 46(6): 2728 - 2733. [Full Text] [PDF]