Allelic Eff ect Variation at Key Photoperiod Response Quantitative Trait Loci in Maize

Tropical maize (Zea mays L.) represents a valuable genetic resource containing unique alleles not present in elite temperate maize. The strong delay in fl owering in response to long daylength photoperiods exhibited by most tropical maize hinders its incorporation into temperate maize breeding programs. We tested the hypothesis that diverse tropical inbreds carry alleles with similar effects at four key photoperiod response quantitative trait loci (QTL) previously identifi ed in maize. Four tropical maize inbreds were each crossed and backcrossed twice to the temperate recurrent parent B73 to establish four sets of introgression lines. Evaluation of these lines under long daylengths demonstrated that all four QTL have signifi cant effects on fl owering time or height in these lines, but the functional allelic effects varied substantially across the tropical donor lines. At the most important photoperiod response QTL on chromosome 10, one tropical line allele even promoted earlier fl owering relative to the B73 allele. Signifi cant allelic effect differences among tropical founders were also demonstrated directly in an F2 population derived from the cross of Ki14 and CML254. The chromosome 10 photoperiod response QTL position was validated in a set of heterogeneous inbred families evaluated in fi eld tests and in controlled environments. N.D. Coles and C.T. Zila, Department of Crop Science, North Carolina State University, Raleigh, NC 27695-7620; J.B. Holland, USDAARS Plant Science Research Unit, Department of Crop Science, North Carolina State University, Raleigh, NC 27695-7620. N.D. Coles present address: Pioneer Hi-Bred International, Woodland, CA 95695. Received 8 Dec. 2010. *Corresponding author ( [email protected]). Abbreviations: ASI, anthesis-silk interval; DTA, days to anthesis; DTS, days to silking; EH, ear height; GDD, growing degree days; GDDTA, growing degree days to anthesis; GDDASI, growing degree days anthesis-silking interval; GDDTS, growing degree days to silking; HIF, heterogeneous inbred family; IBM, intermated B73 × Mo17 population ; NAM, nested association mapping; PH, plant height; SSR, simple sequence repeat; QTL, quantitative trait locus/loci; RIL, recombinant inbred line. Published in Crop Sci. 51:1036–1049 (2011). doi: 10.2135/cropsci2010.08.0488 Published online 29 Mar. 2011. © 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.