Genetic Composition and Spatial Distribution of Farmer-managed Phaseolus Bean Plantings: An Example from a Village in Oaxaca, Mexico

In situ conservation of crop genetic resources is an important complement to ex situ conservation, yet little is known about how small-scale farmers perceive diversity in their own fi elds. In this study, we investigated the role of farmers from a community in the Sierra Juárez, Oaxaca, Mexico, in managing Phaseolus bean diversity in their fi elds. We collected seeds from 287 plants in 10 fi elds in the village of Santa María Jaltianguis and evaluated the diversity present in the collection at 10 nuclear and three chloroplast DNA (cpDNA) microsatellite markers. Following a STRUCTURE analysis, three core population clusters were identifi ed in the collection, a fi nding corroborated by morphological observations, principal coordinate analysis, and neighbor-joining tree construction using molecular data. The fi rst two populations were identifi ed as Phaseolus vulgaris L. ecogeographic races Mesoamerica and Jalisco and the third population as related species Phaseolus coccineus L. and Phaseolus dumosus Macfad. Each of the fi elds sampled consisted predominantly of a single Phaseolus species or ecogeographic race, but there was also evidence of low levels of gene fl ow between races Jalisco and Mesoamerica. Our data suggest farmers in Santa María Jaltianguis recognize existing interand intraspecies diversity in Phaseolus, its differential adaptation, its capacity to exploit a broad range of growing environments, and its potential to buffer the community against socioeconomic and climatic changes. M. Worthington and P. Gepts, Dep. of Plant Sciences, Univ. of California, 1 Shields Ave., Davis, CA 95616-8780; D. Soleri, Geography Dep., Univ. of California, Santa Barbara, CA 93106-4060; F. AragónCuevas, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Campo Experimental Valles Centrales, Santo Domingo Barrio Bajo, Etla C.P. 68200, Oaxaca, México. Received 28 Sept. 2011. *Corresponding author ([email protected]). Abbreviations: cpDNA, chloroplast DNA; FMR, farmer’s fi eld; masl, meters above sea level; NJ tree, neighbor-joining tree; PCR, polymerase chain reaction; PIC, polymorphism information content. Published in Crop Sci. 52:1721–1735 (2012). doi: 10.2135/cropsci2011.09.0518 © 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.