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CROP BREEDING & GENETICS

Genomewide Selection and Marker-Assisted Recurrent Selection in Doubled Haploid versus F₂ Populations

Dep. of Agronomy and Plant Genetics, Univ. of Minnesota, 411 Borlaug Hall, 1991 Upper Buford Cir., St. Paul, MN 55108

^* Corresponding author (bernardo{at}umn.edu).

Molecular markers have been previously found useful for increasing genetic gain in maize (Zea mays L.). The use of doubled haploids (DHs) instead of F₂ plants (or, equivalently, F₃ families) may permit a better estimation of marker–trait associations. Our objective was to determine the usefulness of DH versus F₂ populations in marker-assisted recurrent selection (MARS) and genomewide selection. We simulated testcrosses from a DH population and an F₂ population from the same cross between two inbreds and studied genetic models defined by the number of quantitative trait loci (QTL) and trait heritability (H). Equal-time comparisons of selection response were between Cycle 3 with an F₂ population and Cycle 2 with a DH population. For the genetic model of 100 QTL, H = 0.20 and a population size of N = 100, the ratio of response to selection in DH versus F₂ populations was R_DH:F2 = 109% for genomewide selection and 128% for MARS. For the genetic model of 20 QTL, H = 0.80 and N = 100 these values decreased to 99% for genomewide selection and 109% for MARS. Although genomewide selection was superior to MARS for a given type of population, the advantage of using DH instead of F₂ populations was greater in MARS than in genomewide selection. We concluded that DH populations are most useful in genomewide selection and MARS when many QTL control the trait, H is low, and N is small.

Abbreviations: DH, doubled haploid • MARS, marker-assisted recurrent selection • QTL, quantitative trait loci • R_DH:F2, ratio between the cumulative response to selection in the DH population and the cumulative response to selection in the F₂ population • R_GWS:MARS, ratio between the cumulative response to genomewide selection and the cumulative response to MARS • V_G, genetic variance • V_M, variance explained by markers • V_R, residual variance