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Hybrids of Trifolium pratense L. (2n=14+2) wth T.diffusum Ehrh. (2n=16) and other 16 chromosome Trifolium species

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Strzyzewska C.

Journal of Applied Genetics

1995

vol. 36

issue 1

35-42

12-chromosome forms of red clover (2n=14+2) were crossed to six Trifolium species with the chromosome number 2n=16.Hybrids plants were derived from the cross of s stable 16-chromosome red clover T.pratense with T.diffusum (2n=16).No seeds were obtained from reciprocal crosses.F1 hybrid lantswere morphologically more similar to T.diffusum, whereas their other characters, e.g. flower number per head, were intermediate between the species crossed.All F1 hybrids had the chromosome number 2n=16.Meiosis proceeded with large irregularities.The average number of bivalents per cell was 3.32, and that of univalents -.98.Univalents exibited a high stickiness and frequently formed "end-to-end" configurations chains consisting of about a dozen of so chromosomes.Bivalents were straight.Lagging chromosomes and chromosomes bridges were observed during AI; lagging chromosomes were also found during AII.After an equalizing division,tetrads and different from them microspore polyads were formed.16-chromosome hybrids were male- and female-sterile.No hybrids were obtained from the stable 16-chromosome red clover T.pratense (n=7 chromosomes) crossed to the selected clover species (T.apertum Bobr., T.alexandrium L. and others) with n=8 chromosomes.

Amphidiploid hybrids of Trifolium pratense L. (2n=14+2) with T.diffusum Ehrh. (2n=16)

100%

Strzyzewska C.

After duplicating the chromosome number by colchicine in sterile F1 16-chromosome hybrid T.pratense x T. diffusum some partially fertile plants with 32 chromosomes were found.Male fertility (viability of pollen grain) was from 69.3% to 86.2% , whereas female fertility estimated as seed setting after cross-and self-pollination was 21.8% and 6.9%, resp.Male and female fertility as well as somatic chromosome number were examined in the F2-F4 generations.Selection for female fertility resulted in increasing seed setting in the first two generations (F2 and F3) and in decreasing it in F4 generation.An average seed setting in the F2-F4 generations after cross-pollination amounted to 22.2%, 43.6% and 12.9%, respectvely; after self-pollination it was 25.2%, 27.6% and 1.9%.n the F2 generation all the plants had 2n=32 chromosomes.In the next generations there appeared aneuploids, among which 30-chromosome individuals were predominant.

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2 Journal of Applied Genetics

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Hybrids of Trifolium pratense L. (2n=14+2) wth T.diffusum Ehrh. (2n=16) and other 16 chromosome Trifolium species

Amphidiploid hybrids of Trifolium pratense L. (2n=14+2) with T.diffusum Ehrh. (2n=16)