A Century of Clover Breeding Developments in the United States

Abstract

The perennial clovers, red (Trifolium pratense L.) and white clover (T. repens L.), have been important legumes for livestock feeding in the United States during the past century, particularly in the eastern United States. Recently, sustainable agriculture, organic farming, integrated crop–livestock systems, and high nitrogen prices have stimulated interest in forage legumes. This paper describes the present status of clover improvement programs—their objectives, successes, short falls, and challenges for the future. One goal of most clover breeding programs is increased persistence (longevity of individual plants) because of its association with general adaptability and yield. Persistence, which limits life of clovers to about three to four years, is largely governed by programmed senescence but can be influenced somewhat by breeding for general adaptation to the area of use. New, more‐adapted red clover cultivars have been bred in Wisconsin for use in the northern states, in Kentucky for the middle states, and in Florida for the southern states. For white clover, researchers in several states in the southeast have cooperated in the development of improved cultivars. The unique qualities of these improved species along with high seedling vigor, ease of establishment, and general competitiveness ensure that red and white clover will continue to be the major forage legumes of the United States and justify continued breeding efforts.

Genetic mapping in polyploids

“…are attractive to breeders and consumers alike due to their seedlessness and are usually derived from a tetraploid × diploid cross. In forage species like alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.), tetraploids are generally considered to have favourable agronomic characteristics and are widely employed (Taylor, 2008). Therefore, instead of retreating from the challenges of polyploidy, we could also embrace the developments in technology and bioinformatics which are helping to turn the key to open the polysomic "black box".…”

“…Tetraploid clovers are often favoured over diploids due to their higher yields, greater persistence and higher levels of resistance to biotic and abiotic stresses (Taylor, 2008;Vleugels et al, 2016). However, the main drawback to tetraploid cultivars is their reduced seed yield (Vleugels et al, 2016).…”

Genetic variability of isoflavones in the USDA red clover core collection

“…However, in general isoflavones concentration is not a problem for large ruminants and little research has been conducted on breeding for lower isoflavones content in forage breeding programs in United States (Taylor, 2008). Contrary to large ruminants, high levels of isoflavones have been showed to cause infertility in ewes (Mcdonald, 1995;Moorby et al, 2004) and low phytoestrogens cultivars have been released in Australia and New Zealand (Oram, 1990;Rumball et al, 1997).…”

“…Thus the high level of variation in total isoflavone concentration between cultivars could explain this partially structurxation related to improvement status. Moreover, the breeding schemes and the synthetic structure of the red clover cultivars with several parental families maintain a large within cultivar variation (Taylor, 2008). Papadopoulos et al (2006) showed in their study that total and individual isoflavone concentration in red clover plants presented a high genetic variability among thirteen red clover cultivars, and suggest that selecting individual plant phenotypes for high isoflavones contents would be highly effective for cultivars development.…”

“…Second, the major type of red clover grown worldwide is the early flowering and much of the increased longevity in newly released red clover cultivars is at least partially due to improved disease resistance. (Quesenberry & Casler, 2001;Taylor, 2008). Finally, breeding to improve disease and insect resistance could indirectly rise isoflavonoid amounts since several classes of isoflavonoids acts like phytoalexins and have been showed to be important in pathogen resistance (Dixon, 2001;Samac & Graham, 2007).…”