Genetic Diversity among Wheat Accessions from the USDA National Small Grains Collection

Accessions of common wheat (Triticum aestivum L. subsp. aestivum) from the USDA–ARS National Small Grains Collection (NSGC) are a resource for wheat scientists worldwide. The genetic diversity of the wheat core subset, representing approximately 10% of the collection’s 42,138 T. aestivum accessions, was examined using 390 diversity arrays technology (DArT) markers, 4941 single nucleotide polymorphisms (SNPs), and descriptor data. The marker profiles revealed duplicates, which were excluded to form an informative core (iCore) of 3230 accessions. The iCore population structure and diversity within various subgroups were examined with analysis of molecular variance, principal coordinate analysis, cluster analysis, and by ranking the contribution of individual accessions to overall diversity. Accession groups based on molecular marker data corresponded well to their geographic origin, and population structure was accounted for primarily by differences between Iranian landrace accessions and the rest of the accessions. Accessions classified as breeding lines were overrepresented among those ranked as most diverse based on SNP data, whereas Iranian landraces were underrepresented. Although less diverse as a group, Iranian landrace accessions had a higher frequency of resistance to bunt diseases and Russian wheat aphid compared with the iCore as a whole. The present study provides support for establishing core subsets based on geographic origin of accessions and will be a basis for further study of diversity among NSGC wheats. J.M. Bonman, E.M. Babiker, H.E. Bockelman, K. Esvelt-Klos, and T.C. Gordon, USDA–ARS, Small Grains and Potato Germplasm Research Unit, 1691 South 2700 West, Aberdeen, ID 83210; A. Cuestra-Marcos, Dep. of Crop and Soil Science, Oregon State Univ., Corvallis, OR 97331; G. Brown-Guedira, Plant Science Research Unit, 3411 Gardner Hall, North Carolina State Univ., Raleigh, NC 27695; S. Chao, USDA–ARS Genotyping Lab. , Biosciences Research Lab. , Fargo, ND; D. See, USDA–ARS, Wheat Genetics, Quality, Physiology & Disease Research Unit, Washington State Univ., Pullman WA; J. Chen, Univ. of Idaho Aberdeen Research & Extension Center, Aberdeen ID; E. Akhunov, Dep. of Plant Pathology, Kansas State Univ., Manhattan, KS; J. Zhang, Dep. of Plant Sciences, Univ. of California, Davis, CA. Received 15 Sept. 2014. Accepted 26 Jan. 2015. *Corresponding author (mike.bonman@ars.usda.gov). Abbreviations: AMOVA, analysis of molecular variance; DArT, diversity arrays technology; GRIN, Germplasm Resources Information Network; iCore, informative core; NSGC, National Small Grains Collection; PCoA, principal coordinate analysis; PIC, polymorphism information content; RWA, Russian wheat aphid; SNP, single nucleotide polymorphism. Published in Crop Sci. 55:1243–1253 (2015). doi: 10.2135/cropsci2014.09. 0621 © 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.