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This article in CS

  1. Vol. 51 No. 1, p. 75-83
     
    Received: June 28, 2010


    * Corresponding author(s): lizlee@uoguelph.ca
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doi:10.2135/cropsci2010.06.0378

Nature of the Genetic Variation in an Elite Maize Breeding Cross

  1. A. K. Singha,
  2. T. K. Colemanb,
  3. M. T. Tollenaarc and
  4. E. A. Lee *c
  1. a Semiarid Prairie Agricultural Research Centre, Agriculture and Agri-food Canada, Swift Current, SK
    b Pioneer-Dupont, Woodstock, ON
    c Univ. of Guelph, Dep. of Plant Agriculture, Crop Science Bldg., Guelph, ON, N1G 2W1 Canada

Abstract

Maize (Zea mays L.) breeders through selection have had profound impacts on the maize genome. In this study we examine one aspect of this intense selection pressure, the extent and nature of genetic variation present in an elite maize breeding cross. Specifically genetic variation is examined with regards to genotype × environment interactions (G × E), magnitude of the genetic variance (Vg) estimates, and the underlying grain yield quantitative trait loci (QTL). Using two elite Iodent sister-lines that are 64% identical by descent, 128 recombinant inbred lines (RILs) were generated and testcrossed to a Stiff Stalk inbred line (CG102). Hybrid RILs were grown in 24 trials encompassing 4 yr, three locations, and three planting densities. Additive main effects and multiplicative interaction analysis resolved the trials into eight unique patterns of G × E. Smaller Vg estimates were associated with the more frequently observed patterns of G × E. Nine single-effect QTL and four epistatic interactions were detected across seven of the G × E patterns; however, the single-effect QTL and epistatic interactions were, in general, specific to a G × E pattern. In summary, we found extensive linkage disequilibrium (LD), reduced Vg in the more commonly occurring G × E patterns, and genetic variation due to larger effect epistatic interactions and smaller single effect QTL specific to the G × E pattern. Consequences of the genetic variation are discussed in relation to modern maize breeding programs.

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