Genomewide Selection versus Marker‐assisted Recurrent Selection to Improve Grain Yield and Stover‐quality Traits for Cellulosic Ethanol in Maize

Genomewide selection (GWS) is markerassisted selection without identifying markers with signifi cant effects. Our previous work with the intermated B73 × Mo17 maize (Zea mays L.) population revealed signifi cant variation for grain yield and stover-quality traits important for cellulosic ethanol production. Our objectives were to determine (i) if realized gains from selection are larger with GWS than with markerassisted recurrent selection (MARS), which involves selection for markers with signifi cant effects; and (ii) how multiple traits respond to multiple cycles of GWS and MARS. In 2007, testcrosses of 223 recombinant inbreds developed from B73 × Mo17 (Cycle 0) were evaluated at four Minnesota locations and genotyped with 287 single nucleotide polymorphism markers. Individuals with the best performance for a Stover Index and a Yield + Stover Index were intermated to form Cycle 1. Both GWS and MARS were then conducted until Cycle 3. Multilocation trials in 2010 indicated that gains for the Stover Index and Yield + Stover Index were 14 to 50% larger (signifi cant at P = 0.05) with GWS than with MARS. Gains in individual traits were mostly nonsignifi cant. Inbreeding coeffi cients ranged from 0.28 to 0.38 by Cycle 3 of GWS and MARS. For stover-quality traits, correlations between wet chemistry and near-infrared refl ectance spectroscopy predictions decreased after selection. We believe this is the fi rst published report of a GWS experiment in crops, and our results indicate that using all available markers for predicting genotypic value leads to greater gain than using a subset of markers with signifi cant effects. J.M. Massman and R. Bernardo, Dep. of Agronomy and Plant Genetics, Univ. of Minnesota, 411 Borlaug Hall, 1991 Upper Buford Cir., Saint Paul, MN 55108; H.-J.G. Jung, USDA-ARS Plant Science Research Unit, 411 Borlaug Hall, 1991 Upper Buford Cir., Saint Paul, MN 55108. Received 17 Feb. 2012. *Corresponding author (bernardo@umn.edu). Abbreviations: GWS, genomewide selection; MARS, marker-assisted recurrent selection; NIRS, near-infrared refl ectance spectroscopy; QTL, quantitative trait loci; RR-BLUP, ridge regression–best linear unbiased prediction; SNP, single nucleotide polymorphism. Published in Crop Sci. 53:1–9 (2013). doi: 10.2135/cropsci2012.02.0112 © Crop Science Society of America | 5585 Guilford Rd., Madison, WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher.