Direct and Marker-Assisted Selection for Resistance to Common Bacterial Blight in Common Bean

Common bacterial blight (CBB) caused by Xanthomonas campestris pv. phaseoli and X. campestris pv. phaseoli var. fuscans is a seed-borne disease that can signifi cantly reduce yield and seed quality of common bean (Phaseolus vulgaris L.). Disease resistance is the most effective management strategy, but most common bean cultivars have no CBB resistance. Marker-assisted selection (MAS) shows promise as a method to facilitate pyramiding CBB resistance between common bean gene pools. This study compared the effi ciency of direct disease resistance selection (DDS) and MAS for the pyramiding and transfer of CBB resistance into dark red kidney bean. Direct disease resistance selection and MAS were applied independently, from the F1 through the F5, in an inter-gene pool doublecross population, Wilkinson 2/dark red kidney (DRK) 2//DRK 1/VAX 3. Replicated trials were performed in the greenhouse and fi eld in 2006 and 2007 to assess levels of CBB resistance in 15 breeding lines independently developed with each method. Under high disease pressure, in two greenhouse environments, 12 resistant breeding lines were obtained with DDS compared with six using MAS, and the overall CBB mean disease severity index was 3.3 for DDS and 4.2 for MAS. Under moderate disease pressure in the fi eld, there was no signifi cant difference (p > 0.05) between the responses of breeding lines developed by the two selection methods. The cost of DDS was US$1.55 per plant compared to $2.03 for MAS. R.W. Duncan, Dep. of Plant Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada; R.L. Gilbertson, Dep. of Plant Pathology, Univ. of California, Davis, One Shields Ave., Davis, CA 95616; S.P. Singh, Plant, Soil and Entomological Sciences Dep., Univ. of Idaho, Kimberly Research & Extension Center, 3793 North 3600 East, Kimberly, ID 83341-5076. Received 23 Aug. 2011. *Corresponding author ([email protected]). Abbreviations: CBB, common bacterial blight; DDS, direct disease resistance selection; dpi, days postinoculation; dpp, days post planting; DRK, dark red kidney; DSI, disease severity index; MAS, markerassisted selection; PCR, polymerase chain reaction; QTL, quantitative trait loci; Xcp, Xanthomonas campestris pv. phaseoli. Published in Crop Sci. 52:1511–1521 (2012). doi: 10.2135/cropsci2011.08.0445 © 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.