Reproduced from Crop Science. Published by Crop Science Society of America. All copyrights reserved. 14 WWW.CROPS.ORG CROP SCIENCE, VOL. 48, JANUARY– FEBRUARY 2008 REVIEW & INTERPRETATION F rogeye leaf spot (FLS) is caused by a fungal pathogen, Cerco- spora sojina K. Hara, and is a common disease of soybean [ Glycine max (L.) Merr.] in most soybean-growing countries in the world (Athow and Probst, 1952; Bernaux, 1979; Akem et al., 1992; Ma, 1994). Frogeye leaf spot was irst reported on soybean in Japan in 1915 (Lehman, 1928) and in the United States in 1924 (Melchers, 1925). The disease is most common in the southern U.S. soybean production region but is regularly present in parts of the midwestern United States (Athow and Probst, 1952; Grau et al., 2004). Recently, FLS has moved further northward in the United States. Yang et al. (2001b) conirmed the presence of FLS in Iowa, and Mengistu et al. (2002) reported it in Wisconsin. In 2005 FLS was found in Ohio (Anne Dorrance, personal communication, 2005). It is possible that a combination of warm winter temperatures and cultivation of sus- ceptible soybean cultivars has contributed to the appearance of FLS Frogeye Leaf Spot of Soybean: A Review and Proposed Race Designations for Isolates of Cercospora sojina Hara M. A. R. Mian,* A. M. Missaoui, D. R. Walker, D. V. Phillips, and H. R. Boerma ABSTRACT Frogeye leaf spot (FLS), caused by Cercospora sojina K. Hara, is a common disease of soybean [Glycine max (L.) Merr.] in most soybean-growing countries of the world. Signiicant yield losses of soybean (10–60%) have been attributed to FLS under hot and humid growing conditions. The FLS in the southern United States has been kept under control by planting resistant cultivars. Cercospora sojina is a dynamic pathogen with extensive virulence or race diversity. The current number of C. sojina isolates at the University of Georgia collection is 93. Assigning race desig- nations to this large number of isolates has been dif icult because of the lack of a well-deined set of differentials. To facilitate future studies of the genetics of soybean resistance to FLS and the identiication and comparison of existing and future races of C. sojina, we have reassessed both the soybean differentials and the C. sojina races. Based on the reactions of 93 isolates of C. sojina on 38 putative soybean differentials, we propose a core set of 12 differentials and 11 races that represent the major diversity among the 93 C. sojina isolates. The deinition of these 12 differentials and 11 races should provide the foundation for the identiication and comparison of additional soybean resistance genes and new races of C. sojina. M.A.R. Mian, USDA-ARS and Dep. of Horticulture and Crop Sci- ence, The Ohio State Univ., 1680 Madison Ave., Wooster, OH 44691; A.M. Missaoui, D.R. Walker, and H. R. Boerma, Dep. of Crop and Soil Sciences, Univ. of Georgia, Athens, GA 30602-7272; D.V. Phillips, Dep. of Plant Pathology, Univ. of Georgia–Gri in Campus, Gri in, GA 30223. A.M. Missaoui, current address: Monsanto Co., 1551 Hwy. 210, Huxley, IA 50124; D.R. Walker, current address: USDA-ARS Soybean Germplasm, Pathology & Genetics Unit, Urbana, IL 61801. Received 4 Aug. 2007. *Corresponding author (mian.3@osu.edu). Abbreviations: AFLP, ampli ied fragment length polymorphism; AUDPC, area under disease progress curve; BSA, bulked segregate analysis; cM, centimorgan; FLS, frogeye leaf spot; LAD, leaf area dam- aged; LG, linkage group; NIL, near-isogenic line; RAPD, random ampli ied polymorphic DNA; RFLP, restriction fragment length poly- morphism; SSR, simple sequence repeat. Published in Crop Sci. 48:14–24 (2008). doi: 10.2135/cropsci2007.08.0432 © 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.