Registration of ‘FL24D’, a Red Clover Selected for Tolerance to 2,4-D Herbicide

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 significant 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 flowering experiment revealed that FL24D was 25 d earlier to 50% flowering than Southern Belle and 20 d earlier to 95% flowering 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 affect yields of cultivars that do not have tolerance to 2,4‐D.

Cost-effective detection of genome-wide signatures for 2,4-D herbicide resistance adaptation in red clover

“…Resistance to herbicides with complex modes of action, such as 2,4-D, is indeed likely to be affected by many genes with minor-effects, arising gradually in the population via recombination of standing genetic variants into the same genetic background over generations 1,23,37,38 . The quantitative genetic architecture of 2,4-D resistance in red clover is also in agreement with the breeding strategy employed to obtain resistant plants, where recurrent cycles of mass selection under 2,4-D application were carried out to increase the number of favorable alleles in the population 12,30,39 . However, monogenic and dominant patterns of inheritance were inferred through segregation studies of the 2,4-D resistance phenotype in some weed species, such as wild mustard ( Brassica kaber L.), prickly lettuce ( Lactuca serriola L.), oriental mustard ( Sisymbrium orientale L.), and wild radish ( Raphanus raphanistrum L.) 40–44 .…”

“…Despite being widely used for more than 70 years, few species have naturally evolved resistance to 2,4-D 6,9 . To our knowledge, there are 16 cases of 2,4-D resistance in dicot weeds and two resistant crops obtained by traditional breeding reported to date 10–12 . The absence of widespread resistance adaptation to 2,4-D is likely due to its complex mode of action, with many avenues of functional redundancy and fitness penalties of mutations in its pathways 13 .…”

“…Red clover ( Trifolium pratense L.) is a forage legume crop that has been bred for 2,4-D tolerance because this herbicide is one of the most commonly used for weed control in grass pastures 12 . The tolerant cultivar ‘FL24D’ was developed at the University of Florida after six cycles of recurrent mass selection for tolerance to 2,4-D 12 . When susceptible and tolerant plants are sprayed with 2,4-D, the former ones die, while the tolerant plants show strong damage but regrow from the crown meristematic tissue.…”

Grassland Management Affects Delivery of Regulating and Supporting Ecosystem Services

“…Recent technological innovations that may enhance legume use include novel establishment approaches (e.g., strip planting into existing grass swards; Castillo et al, 2013;Mullenix et al, 2014) and management techniques to reduce competition from grasses (e.g., spatial separation of grass and legume; Solomon et al, 2011). New developments like 2,4-dichlorophenoxyacetic acid-resistant red clover (Quesenberry et al, 2015) provide greater opportunity for broadleaf weed control in swards containing legumes. A number of interesting questions remain relative to legumes and ES, including what proportion of herbage mass should be contributed by legumes to optimize delivery of ES and reduce C footprint.…”

Registration of ‘FF 9615’ Red Clover

“…Both can also be used in conjunction with seeking US Plant Variety Protection, although only a few public red clover cultivars have sought Plant Variety Protection. Since 2008, the following red clover cultivars have been registered in the Journal of Plant Registrations : ‘AU Red Ace’ (Mosjidis, 2011), ‘Barduro’ (Quesenberry and Blount, 2012), ‘FL24D’ (Quesenberry et al, 2015), and Freedom!MR (Taylor, 2008). Since 2008, the following red clover cultivars have gone through the AOSCA variety review board: ‘Bearcat’ (2016), FF 9615 (2013, 2015), ‘FSG 401RC’ (2012, 2014), ‘FSG 402’ (2013), ‘Gallant’ (2012, 2013), ‘Resilience’ (2017), ‘Rustler’ (2012), and ‘SS‐0303RCG’ (2012, 2014).…”