CROP SCIENCE, VOL. 49, JANUARY– FEBRUARY 2009 187 RESEARCH C ommon bean (Phaseolus vulgaris L.) is a diploid (2n = 2x = 22) annual, predominantly self-pollinating, determinate, semi- determinate, or indeterminate plant type (Evans, 1976). After America was discovered, common bean was widely distributed in Europe and the Mediterranean area, where it was grown for dry seeds or fresh pods (Zeven, 1997; Papa et al., 2006). In Italy, where a large number of landraces evolved in response to the environment and to selection by farmers, genetic erosion took place. However landraces are still grown in remote areas with low-input agriculture for direct use by farmers (Lioi et al., 2005). Genetic variation in common bean has been widely characterized using morphological traits (Singh, 1988; Escribano et al., 1998) and biochemical markers (Gepts, 1988; Singh et al., 1991; Logozzo et al., 2007). At the DNA level, landraces, cultivars, and breeding varieties from the two cen- ters of origin and other environments have been fingerprinted. The molecular markers that have been used are random amplified polymorphic DNA (Kami and Gepts, 1994; Beebe et al., 2000), Analysis of Genetic Structure in Widely Distributed Common Bean Landraces with Different Plant Growth Habits Using SSR and AFLP Markers P. Masi, G. Logozzo, P. Donini, and P. Spagnoletti Zeuli* ABSTRACT The genetic variation in common bean (Phaseo- lus vulgaris L.) landraces with different growth habits, which are grown over a wide and environ- mentally heterogeneous area in southern Italy, was studied to help define strategies for con- servation of genetic resources. Accessions of three landraces, a’Marrozzo and Poverella with indeterminate growth habits, and Verdolino with a determinate growth habit, were scored for 30 simple sequence repeat (SSR) and 393 amplified fragment length polymorphism (AFLP) loci using eight primer combinations. Very low heterozy- gosity was observed, and all 73 plants analyzed showed different genotypes when comparing their alleles at the SSR or AFLP loci. The ana- lyzed genotypes were clustered first according to plant growth habit and then in distinct groups according to landrace classification. Genetic differentiation among landraces was higher for AFLP (F ST = 0.64) than for SSR loci (F ST = 0.31), and variation within landraces was higher in a’Marrozzo, which is widely distributed over four river catchment basins. The proportion of alleles common to all three landraces was much larger for AFLP (62.34%) than for SSR (27.13%), while the alleles found in only one landrace were more frequent for SSR (47%) than for AFLP (8.14%). The large number of SSR and AFLP alleles shared between a’Marrozzo and Poverella (both with indeterminate growth habits) indicates their common evolutionary history. P. Masi, G. Logozzo, and P. Spagnoletti Zeuli, Dipartimento di Bio- logia, Difesa e Biotecnologie Agro-forestali, Università degli Studi della Basilicata, Viale dell’Ateneo Lucano, 10-85100 Potenza, Italy; P. Donini, Molecular Research Group, NIAB, Cambridge CB3 0LE, U.K.; current address: Applied Research Dep., Philip Morris Inter- national, Research and Development, Quai Jeanrenaud 56, 2000 Neuchâtel, Switzerland. Received 15 May 2008. *Corresponding author (pierluigi.spagnoletti@unibas.it). Abbreviations: AFLP, amplified fragment length polymorphism; AMOVA, analysis of molecular variance; PCR, polymerase chain reac- tion; RFLP, restriction fragment length polymorphism; SDI, Shannon– Weaver diversity index; SSR, simple sequence repeat. Published in Crop Sci. 49:187–199 (2009). doi: 10.2135/cropsci2008.05.0265 © 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.