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Tetraploid and Triploid Interspecific Hybrids of Trifolium pratense L., T. diffusum Ehrh., and Some Related Species 1
Author(s) -
Schwer J. F.,
Cleveland R. W.
Publication year - 1972
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1972.0011183x001200040006x
Subject(s) - biology , hybrid , meiosis , backcrossing , botany , population , ploidy , chromosome , genetics , interspecific hybrids , reciprocal cross , gene , demography , sociology
Tetraploid hybrids were produced from matings of 4x Tritolium pratense L. by 4x T. dilfusum Ehrh., but not from the reciprocal cross. F 1 and F 2 plants were moderately vigorous and fertile and had very similar morphology. Few examples of phenotypic segregation were found in the F 2 families. Backcross plants ( T. pratense ✕ F 1 ) were sterile. Meiosis of 4x hybrids was characterized as follows: (i) hybrids had proportionately more bivalents at than did the autoploid parents; (ii) bivalents were usually the ring type; (iii) multivalents with from three to 18 Chromosomes occurred at MI; (iv) univalents were present at MI and laggard chromosomes at AI and AII; and (v) bridges with fragments were found at AI The meiotic behavior of the tetraploid hybrids appeared to be consistent with that expected for newly constituted segmental allopolyploids. However, the breeding behavior of hybrids approached that of genomic allopolyploids. In explanation, the majority of functional gametes of the F 1 may have come from cells with completely homogenetic chromosome pairing. A hypo‐triploid hybrid (2n = 21) was obtained from matings of 4x T. pratense by 2x T. diffusum . The plant was vigorous, and partially fertile. A phenotypically variable population was produced from the F 1 by openpollination with 2x T. pratense . The F 1 had the following meiotic behavior: (i) cells at MI averaged five bivalents and five univalents; (ii) low frequencies of multivalents occurred in units of 3 to 10 chromosomes; (iii) laggards were common at AI and AII; and (iv) single bridges with fragments occurred infrequently at AI and AII. Heterogenetic associations at MI were somewhat more frequent in the T. pratense ✕ T. diffusum hypo‐triploid than in the T. pratense ✕ T. pallidum triploid, previously reported. Thus, the chromosomes of T. pratense seemed to have more pairing affinities with those of T. diffusum than with those of T. palliclum . One morphologically abnormal, sterile hybrid was produced from 4x T. pratense mated with 2x T. hirtum All. Its somatic chromosome numbers were variable in roottip cells. Two phenotypically different hybrids were obtained from 4x T. pratense mated with 2x T. pallidum Waldst. & Kit. One plant was partially fertile; the other, sterile.