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This article in CS

  1. Vol. 20 No. 1, p. 35-42
    Received: Mar 21, 1979

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A Comparison of Replicated S1 per se vs. Reciprocal Full-Sib Index Selection in Corn. I. Indirect Response to Population Densities1

  1. D. R. West,
  2. W. A. Compton and
  3. M. A. Thomas2



Two cycles of S1 per se selection have been completed in each of three corn (Zea mays L.) populations: Nebraska B Synthetic (NBS), Nebraska Stiff Stalk Synthetic (NSS), and improved Nebraska Krug variety (NKS). In addition, two cycles of reciprocal full-sib recurrent selection (RFS) have been completed between NBS and NSS and between NBS and NKS. Each selection scheme was replicated three times. Selection was based on an index (resulting in a calculated value of yield on standing plants) and on yield trials generally grown at 51,666 plants/ha. Response at 68,888 and 17,222 plants/ha (called here indirect density response) is reported in this study. Each replicate of each selection procedure was grown as an S1 random mating (RM), or variety cross population. Index values of cycle 2 (C2.) were increased 20% or more over C0 in tests of bulked S1 populatgons selected by S1 per se performance while response to RFS selection varied from an increase of 9% in C2 of NKS to a negative response of −10% in NBS. Significant selection ✕ plant populaion density effects were found only in the random mating test of the NKS population. Response to S1 per se selection was significantly greater than response to RFS selectlon in the NBS random mating population, but response to the two methods did not differ in NSS or NKS grown as random mating populations.

Index means of variety crosses of C2 were approximately 12% above C0 variety crosses and there were no differences between selection methods. The evaluation of selection response indicated that in the early cycles of selection, response to selection at one plant density will be unchanged when selection products are grown at other plant densities. Response to S1 per se selection was greater than RFS selection response in bulk S1 and RM evaluations, but the RFS and S1 per se methods resulted in equal improvement of variety cross performance.

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