Breeding potential of the backcross progenies of a hybrid between Trifolium medium × T. pratense to T. pratense

Abstract

Breeding potential of the backcross progenies of a hybrid between Trifolium medium × × T. pratense to T. pratense. Can. J. Plant Sci. 82: [395][396][397][398][399]. In this study, T. medium (zigzag clover, 2n = 80 and T. pratense (red clover, 2n = 28) were hybridized and backcrossed four times to T. pratense (BC 1 , BC 2 , BC 3 and BC 4 ), and the seed production and vigor of the backcross progenies were assessed under field conditions. Both female and pollen fertility of the backcross progenies increased as the backcross generations advanced. Female and pollen fertility of BC 4 were 21.3 and 65.3%, respectively. When honeybees were used as pollinators, almost all BC 4 plants produced mature seeds in the field. Most of the BC 1 , BC 2 , and BC 3 plants died by the end of the fourth year in the field, whereas 61% of the BC 4 plants survived for 4 yr. The number of chromosomes in 79% of the BC 4 plants was more than 28, which is greater than that of T. pratense. Mots clés: Rétrocroisement, matériel génétique, hybridation interspécifique, Trifolium medium, Trifolium pratenseTrifolium pratense L. (red clover) is an important forage legume in the northern part of Japan because it is easy to cultivate due to high adaptability to acidic and humid conditions. However, its usefulness is limited due to its lack of perenniality, which is a common deficiency of T. Pratense throughout the world. Introgression of genes for longevity from perennial Trifolium species to T. pratense is a potential means for improving the persistence of T. pratense. Various hybridizations with T. pratense have been carried out with several species: T. pallidum [Palestine clover (Armstrong and Cleveland 1970)], T. diffusum (Taylor et al. 1963;Schwer and Cleveland 1972), T. hirtum [Rose clover (Schwer and Cleveland 1972)], T. sarosiense Collins et al. 1983), T. alpestre [Purple glove clover (Merker 1988;Phillips et al. 1992)], and T medium [Zigzag clover (Merker 1982);Nedbalkova et al. 1995;Sawai et al. 1990Sawai et al. , 1995. Although many hybrids have been successfully produced, there have been no reports of hybrid plants being used as germplasm in conventional breeding programs. The reason for this lack of use is that the plants have not shown sufficient levels of fertility and vigor to justify employing them as practical breeding materials. Anderson et al. (1991) produced third backcross progenies of hybrids between T. ambiguum (Kura clover) × T. repens (White clover) to T. repens, and succeeded in increasing their fertility to a sufficient level for direct use in forage production. Their study showed that backcrossing is an effective means for increasing fertility and vigor.To introduce the rhizomatous growth habit and perenniality from T. medium to T. pratense, Sawai et al. (1995) obtained first and second backcross progenies of the hybrid between T. medium × T. pratense to T. pratense. The fertility of the backcross progenies increased as their generations advanced. However, neither the fertility nor the vigor were adequate for use in a ...

Impact of interspecific hybridization of T. pratense × T. medium and backcrossing on genetic variability of progeny

“…In contrast to the fifth generation (Řepková et al 2003), the majority of plants today possess 2n = 28 chromosomes. This shows a strong tendency to stabilize the unbalanced genomes into the maternal state, as was previously reported also in clover (Isobe et al 2002) as well as in other crop plants (RennyByfield & Wendel 2014). Aside from plants with 2n = 28 chromosomes, a significant proportion of differing chromosome counts dissimilar to both parents was recognized in both generations (24.0% in JEH1V and 34.3% in JEH1F).…”

“…The only examination was performed on the fifth hybrid generation by means of flow cytometry measurement, which showed DNA content corresponding to the range of 30-45 chromosomes (Řepková et al 2003). Subsequent hybrid generations were not examined at all and their genetic states have so far remained unknown, even though the previous reports of clover hybrids had observed genomic instability among successive generations leading to the loss of chromosomes (Isobe et al 2002).…”

Variation of morphological and agronomic traits in hybrids of Trifolium pratense × T. medium and a comparison with the parental species

“…In our opinion, the prevailing dominance of T. pratense traits in hybrids is a consequence of repeated backcrosses. This corresponds to the results of Isobe et al (2001), who observed different leaf morphologies between BC 4 plants and T. pratense in the same cross combination in comparison with the parental species. The intermediate morphological appearance of interspecific hybrids was also observed in other species combinations, such as T. alexandrinum × T. apertum , T. alexandrinum × T. constantinopolitanum and T. alexandrinum × T. resupinatum (Kaushal et al 2005).…”

Modern methods for genetic improvement of Trifolium pratense.

“…T. pratense has been successfully crossed with five species so far (reviewed by Abberton 2007): T. sarosiense Hazsl. (Collins et al 1981;Phillips et al 1982), T. medium L. (Collins et al 1981;Vogt & Schweiger 1983;Merker 1984;Sawai et al 1990;Isobe et al 2002;Nedbalkova et al 1995), T. alpestre L. (Collins et al 1981;Merker 1988;Phillips et al 1992), T. ambiguum M.Bieb. (Vogt & Schweiger 1983) and T. diffusum Ehrh.…”