CROP SCIENCE, VOL. 49, JULY– AUGUST 2009 1313 RESEARCH S oybean [ Glycine max (L.) Merr.] is the world’s most impor- tant oilseed crop. Soybean seed comprises ~20% oil and 40% protein. The nutritional quality of soybean protein is the highest among plant sources (Henley and Kuster, 1994; Young, 1991). Soybean also contains phytochemicals known as isolavones. Iso- lavones are classi ied as phytoestrogens because of the similarity in chemical structure with mammalian hormone estrogen. Pre- vious studies have reported on the beneicial health attributes of isolavones. Isolavones may act as estrogenic compounds, anties- trogenic compounds, and as antioxidants (Messina, 1999). Isola- vones play a role in preventing coronary heart disease, preventing speci ic cancers and osteoporosis, and have the ability to attenuate many menopausal symptoms (Setchell, 1998). Recently, however, the American Heart Association, in a review of 22 randomized trials, reported little supporting evidence for health beneits asso- ciated with soybean protein and/or soybean isolavone (Sacks et al., 2006). The impact of isolavone on human health continues Genotype × Environment Interaction and Stability for Isolavone Content in Soybean Sheila E. Murphy, Elizabeth A. Lee, Lorna Woodrow, Philippe Seguin, Jagdish Kumar, Istvan Rajcan, and Gary R. Ablett* ABSTRACT Isolavones are naturally occurring compounds found in soybean [Glycine max (L.) Merr.]. Soy- bean isolavone, as a quantitative trait, is subject to signiicant genotype × environment interac- tion, which makes breeding for this trait dif icult. Thirty F 4:7 soybean lines, derived from crosses of ‘RCAT Angora’ × CK-01 and ‘Heinong 35’ × RCAT Angora were classiied within each popu- lation as high, intermediate, or low isolavone. The lines, parents, and two maturity checks were grown in four locations in 2005 and six locations in 2006 across Ontario and Quebec, Canada. Isolavone content of the mature seed was determined by near-infrared relectance. The effects of genotype, environment, and the genotype × environment (G × E) interaction were signiicant. Consistently performing genotypes from the two populations were identiied by sev- eral stability parameters. Genotype–genotype × environment (GGE) biplot demonstrated an ability to provide information on both the geno- types and the environments in which they were evaluated. The identiication of genotypes with consistent placement in either the high- and low-isolavone classes suggested that breed- ing for relative isolavone content in soybean is possible, although breeding for absolute stabil- ity remains a challenge, given the large environ- mental inluence on soybean isolavone levels. S.E. Murphy, E.A. Lee, and I. Rajcan, Dep. of Plant Agriculture, Univ. of Guelph, Guelph, ON N1G 2W1 Canada; L. Woodrow, Agriculture and Agri-Food Canada, 2585 Hwy. 20 East, Harrow, ON N0R 1G0 Canada; P. Seguin, Dep. of Plant Science, McGill Univ., Ste. Anne de Bellevue, QC H9X 3V9 Canada; J. Kumar, Hendrick Seeds, 11791 Sandy Row, Inkerman, ON K0E 1J0 Canada; G.R. Ablett, Ridgetown Cam- pus, Univ. of Guelph, Ridgetown, ON N0P 2C0 Canada. This work was submitted by S.E. Murphy in partial ful illment for the Masters degree from the Dep. of Plant Agriculture, at the Univ. of Guelph. Received 12 Sept. 2008. *Corresponding author (gablett@uoguelph.ca). Abbreviations: G × E, genotype × environment; GGE, genotype– genotype × environment; PC, principal component. Published in Crop Sci. 49:1313–1321 (2009). doi: 10.2135/cropsci2008.09.0533 © Crop Science Society of America 677 S. Segoe 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.