CULTIVAR 288 JOURNAL OF PLANT REGISTRATIONS Registration of ‘FL24D’, a Red Clover Selected for Tolerance to 2,4-D Herbicide Kenneth Quesenberry,* Ann Blount, Patricio Munoz, Jason Ferrell, and Jose Dubeux Copyright © 2015 Crop Science Society of America. 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. Journal of Plant Registrations 9:288–293 (2015). doi:10.3198/jpr2014.11.0081crc Received 25 Nov. 2014. Accepted 29 Mar. 2015. Registration by CSSA. 5585 Guilford Rd., Madison, WI 53711 USA *Corresponding author (clover@ul.edu) Abstract ‘FL24D’ (Reg. No. CV-33 PI 673130) red clover (Trifolium pratense L.) is a synthetic cultivar selected for tolerance to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), and it is the most nondormant red clover cultivar available in today’s market. Red clover can experience signiicant broad- leaf weed competition, especially during the establishment phase of a sward. Most such weeds can be controlled in grass-based forage systems with inexpensive herbicides such as 2,4-D since most grass species are naturally tolerant. However, 2,4-D is not a herbicide option in red clover that is sensitive to this herbicide. Beginning with a broad-based red clover germplasm, six cycles of selection for tolerance to 2,4- D were conducted, leading to the development of FL24D. In a greenhouse experiment comparing response of FL24D to ‘Southern Belle’ (a 2,4-D-sensitive cultivar) at a 1.06 kg ha −1 rate, FL24D rated 7.0 whereas Southern Belle rated 1.2 (where 9 = no damage and 1 = dead plant). A lowering experiment revealed that FL24D was 25 d earlier to 50% lowering than Southern Belle and 20 d earlier to 95% lowering than Southern Belle. Results from several cultivar evaluation experiments show that under sward conditions, application of 2,4-D herbicide at the recommended rate did not decrease yields of FL24D but did afect yields of cultivars that do not have tolerance to 2,4-D. K. Quesenberry, P. Munoz, and J. Ferrell, Agronomy Dep., Univ. of Florida, P.O. Box 110500, Gainesville, FL 32611; A. Blount and J. Dubeux, North Florida Research and Education Center, Univ. of Florida, 3925 Hwy. 71, Marianna, FL 32446. ‘F L24D’ (Reg. No. CV-33, PI 673130) red clover ( Trifo- lium pratense L.) was selected for tolerance to the her- bicide 2,4-dichlorophenoxyacetic acid (2,4-D). his cultivar was developed and released by the Agronomy Depart- ment unit of the Florida Agricultural Experiment Station and was released in 2014. FL24D is particularly distinctive among red clover cultivars in that it has the combination of a high level of tolerance to 2,4-D and being highly nondormant. Red clover is an important forage legume on a worldwide basis, second only to alfalfa (Medicago sativa L.). Various research reports from Florida and other southeastern US states dating back to the 1950s and 1960s showed that red clover had excellent cool-season yield in late winter and spring, but it was much later in spring growth and distribution of dry matter yield than crimson clover ( T. incarnatum L.). Most of this research used winter dormant cultivars developed from mid- and upper- transitional zone states such as Kentucky and Indiana. Winter dormancy in red clover is suggested to be a response to decreasing daylength in fall and also afected by decreasing soil temperatures. Conversely, release from dormancy and initiation of spring growth is suggested to be a response to lengthening days and increases in soil temperatures in spring (Kendall and Stringer, 1985). Marked variability in this photoperiod response has been observed among red clover cultivars and is believed to be quantitatively inherited (Quesenberry and Blount, 2012). he University of Florida forage breeding program has released less-dormant cultivars (‘Cherokee’ [Quesenberry et al., 1993] and ‘Southern Belle’ [Quesenberry et al., 2005]), with earlier initiation of spring growth, and an intermediate-early cultivar ‘Barduro’ (Quesenberry and Blount, 2012). However, even Southern Belle is markedly later in production than crimson clover, and it has been suggested that an even earlier producing red clover would be desirable. To date, dormancy has not been associated with other speci ic agronomic attributes of red clover. Cool-season forage species grown in the southeastern United States are typically reestablished on an annual basis, Abbreviations: 2,4-D, 2,4 dichlorophenoxyacetic acid. Published May 8, 2015