Interspecific Trifolium Hybrids Produced by Embryo and Ovule Culture

Abstract

White or ladino clover (Trifolium repens L.) is an important forage or legume worldwide. However, lack of drought tolerance and disease resistance limit its usefulness. Although other Trifolium species express these traits, routine crossing to develop interspecific hybrids and introduce desirable traits has achieved limited success. The objective of this work was to culture embryos and ovules to rescue hybrids and regenerate plants in new interspecific hybrid combinations. A media regime is described that is generally useful with Trifolium hybrid embryos at the torpedo stage or later. Novel interspecific combinations include T. ambiguum Bieb. with T. montanum L. and T. occidental Coombe; T. isthmocarpum Brot. with T. repens and T. nigrescens Viv.; a trihybrid, designated RUO, of T. repens, T. uniflorum L., and T. occidentale with hexaploid T. ambiguum. The RUO‐T. ambiguum hybrid was produced in several genotypic combinations, one of which bloomed and yielded viable pollen. Interspecific hybridization in Trifolium offers a route to enhancement of forage germplasm by introducing traits that increase longevity while maintaining the superior forage quality of T. repens.

Interspecific hybridization of Trifolium alexandrinum with T . constantinopolitanum using embryo rescue

“…However, in the present study, MS basal medium was found to be better for embryo growth and regeneration in T. alexandrinum than L2 basal medium. Ferguson et al (1990) also found MS basal medium to be best culture medium in many Trifolium interspecific crosses.…”

“…Evans (1962) reported the existence of a high degree of incompatibility between species of Trifolium and advocated the embryo culture method for salvaging hybrid embryos. Embryo culture has been used as an effective tool for developing interspecific hybrids involving such various Trifolium species as T. ambiguum, T. montanum, T. occidentale, T. esthocarpum, T. repens, T. nigrescens, T. uniflorum and T. sarosiense (Williams and Verry 1981;Phillips et al 1982Phillips et al , 1992Yamada and Fukuoka 1986;Pandey et al 1987;Przywara et al 1989;Ferguson et al 1990;Sawai et al 1990Sawai et al , 1995. However, limited success in interspecific hybridization involving T. alexandrinum as the female parent has been reported (Trimble and Hovin 1960;Evans 1962;Selim et al 1977).…”

Future options and targets for pasture plant breeding in New Zealand

“…White clover does not usefully hybridise in nature with any other species (Williams et al 2006a). It has been artificially hybridised with only four of its near relatives (T. nigrescens, T. occidentale, T. isthmocarpum, and T. uniflorum) (Pandey et al 1987;Ferguson et al 1990) to produce fertile plants. However, no breeding programmes were developed to exploit these hybrids.…”

Caucasian clover (Trifolium ambiguum Bieb.) × white clover (T. repens L.) – interspecific hybrids developed through tissue culture

“…Tissue culture like embryo rescue have been applied extensively to reproductive battier overcoming of clover and other species (Roy et al, 2004;Barikissou and Baudoin, 2012). The use of interspecific hybridization and tissue culture have been successfully developed to produce F l hybrids between tetraploid caucasian clover and white clover in order to combine the superior characteristics of both clovers (Ferguson et al, 1990;Anderson et al, 1991). A range of backcross hybrids, using white clover as the recurrent parent, has been generated and by the third generation of backcrossing, plants that are very similar to white clover but with rhizomes as well as stolon have been produced (Abberton et al, 1998).…”