Interspecific Hybridization in Trifolium
1967
Katznelson, J.
The interspecific relationships among several Trifolium spp. in the section Calycomorphum were studied. Crosses involving T. israeliticum, T. globosum, and T. pauciflorum failed to produce hybrid seed. Crosses among T. subterraneum, T. eriosphaerum, and T. pilulare gave varying results. Complete interspecific sterility was most common; however, 3 F₁ plants (1 plant from the T. eriosphaerum ✕ T. subterraneum cross and 2 plants from the T. pilulare ✕ T. subterraneum cross) survived till after flowering. The F₁ plants had morphological characteristics of both parents. F2 seeds were formed, probably through backcrossing, in two male sterile interspecific hybrids, T. subterraneum ✕ T. eriosphaerum and T. pilulare ✕ T. subterraneum. Fertility was partially restored in the F₃ and F₄ lines, although several fertile F₃ plants produced sterile progenies. The results suggest that this group is young and shares common morphogenetical and physiological systems because interspecific hybrids can be obtained by conventional methods. Morphological specialization is more advanced than the reproduction barriers because the taxa involved are self-fertilized annuals and are isolated spatially.
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