Interspecific Hybridisation Between Trifolium repens and T. uniflorum

Abstract

Several partially fertile hybrids (2n = 32) were produced by embryo culture from crosses of the type T. repens (2n = 32) female × T. uniflorum (2n = 32) male . The reciprocal crosses, although giving better seed development in vivo, were less successful in producing viable hybrid plants. Backcrosses to both parent species and F₂ hybrids were also produced. Hybrid materials were variable with respect to morphological characteristics but broadly within the expected intermediate range. Their root systems were generally coarser and deeper than that of T. repens, offering the prospect of improved resistance to beetle larvae and drought. One F₁ hybrid proved to be highly self-compatible, although derived from self-incompatible parent species. Pollen fertility ranged from 0 to 58% for F₁ hybrids, 0 to 13% for F₂ hybrids, 0 to 84% for backcrosses to T. repens and 0 to 26% for backcrosses to T. uniflorum. Marked seasonal variations in pollen fertility were also observed. Up to two quadrivalent chromosome associations per pollen mother cell were observed at meiosis in F₁ hybrids, indicating some intragenomic pairing of T. repens chromosomes. Quadrivalent associations were also observed in an F₂ hybrid and three backcrosses to T. repens.