Heritability and Genetic Variance Estimates for Resistance to Downy Mildew in Cucumber Accession Ames 2354

Downy mildew (DM) of cucumber (Cucumis sativus L.), caused by Pseudoperonospora cubensis, is a devastating disease of cucurbits. resistance is available but is not sufficient to eliminate the need for fungicides to control the disease. previously, the USDA plant Introduction collection of cucumber germplasm was screened in poland and North Carolina, and Ames 2354 was identified as highly resistant. The objectives of this study were to develop an effective method for measuring resistance to DM and to determine the type of gene action controlling resistance in Ames 2354. plant Introduction 175695 was used as the susceptible parent in crosses with Ames 2354 to make seven generations for study: p1, p2, F1, F1 reciprocal, F2, BC1p1, and BC1p2. Additive effects were more important than dominant effects in our study with resistance attributed to a few major loci. Greenhouse testing methods were identified that can be used in selecting for improved resistance. Selection using the best test methods could lead to a gain of at least 2.5 points (on a 10 point scale) per generation even under the lower selection intensities (i.e., 20%) typically used in recurrent selection programs. E.U. Kozik and U. Klosińska, Research Institute of Horticulture, Dep. of Genetics, Breeding and Biotechnology, 96-100 Skierniewice, Poland; A.D. Call and T.C. Wehner, North Carolina State Univ., Dep. of Horticultural Science, Raleigh, NC 27695-7609. Received 16 May 2012. *Corresponding author ([email protected]). Abbreviations: DM, downy mildew; DSI, disease severity index. Published in Crop Sci. 53:177–182 (2013). doi: 10.2135/cropsci2012.05.0297 © 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.