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This article in CS

  1. Vol. 38 No. 5, p. 1164-1174
     
    Received: June 30, 1997


    * Corresponding author(s): knapps@css.orst.edu
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doi:10.2135/cropsci1998.0011183X003800050009x

Marker-Assisted Selection as a Strategy for Increasing the Probability of Selecting Superior Genotypes

  1. Steven J. Knapp
  1. Crop Sci., Bldg. 451C, Dep. of Crop and Soil Science, Oregon State Univ., Corvallis, OR 97331

Abstract

Abstract

Marker-assisted selection (MAS) has been shown, in theory, to produce greater selection gains than phenotypic selection for normally distributed quantitative traits. Theory is presented in this paper for estimating the probability of selecting one or more superior genotypes by MAS (PrMAS). This paramater was used to estimate the cost efficiency of MAS relative to phenotypic selection (Ec). PrMAS and Ec are functions of heritability (h2), heritability of a MAS index (h2I), the phenotypic selection threshold (i), the genotypic superiority threshold (g), and p = σ2M2G, where σ2M is additive genetic variance associated with markers and 2G is additive genetic variance, h2I increases as p increases. Heritability can be increased to 1.0 by increasing p to 1.0; however, estimated marker effects (p̂) and true quantitative trait locus effects (p) must be perfectly correlated to achieve this in practice. PrMAS increases throughout the range of p when i ≥ g, decreases as g increases, and increases as i increases for most p. The frequency of superior genotypes among selected progeny increases as selection intensity increases. Ec ranged from 1.0 to 16.7 for i and g from 1.282 to 2.326, h2 from 0.1 to 1.0, and p from 0.0 to 1.0; thus, a breeder using phenotypic selection must test 1.0 to 16.7 times more progeny than a breeder using MAS to be assured of selecting one or more superior genotypes. Ec increases as g or iincrease and h2 decreases and increases asp increases when i = g. Ec predicts that MAS substantially decreases the resources needed to accomplish a selectiOn goal for a low to moderate heritability trait when the selection goal and the selection intensity are high.

This work was funded by a grant from the USDA NRICGP (90-43213-5190). Oregon Agric. Exp. Stat. Tech. Paper No. 11,198.

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