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1

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

100%
Strzyzewska C.
Journal of Applied Genetics
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1995
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vol. 36
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issue 2
147-154
EN
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.
2

Cytological investigations of the interspecific hybrids of Nicotiana tabacum L. ? N. glauca Grah.

86%
Trojak-Goluch A., Berbec A.
Journal of Applied Genetics
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2003
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vol. 44
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issue 1
45-54
EN
Interspecific amphihaploid and amphidiploid hybrids between Nicotiana glauca Grah. (2n = 24) and N. tabacum L. (2n = 48) cultivars BY 103 and K 326 were analysed. F1 amphihaploids (2n = 36) were viable and completely self- and cross-sterile, and mostly univalents were present during meiosis (with pairing range from 0 to 5). In some meiocytes, meiotic irregularities were observed, such as sporadic chromatin bridges and formation of restitution nuclei. The resultant F1 hybrids were easily converted to amphidiploids (2n = 72) via colchicine treatment of seedlings. The number of univalents and the frequency of PMCs containing unpaired chromosomes indicated that amphidiploids N. tabacum cv. BY 103 or K 326 ? N. glauca represented quite a high pairing category. However, they were male sterile because pollen mother cells were arrested at the tetrad stage. The termination of development of PMCs, and consequently male sterility, are very rare in this kind of tobacco hybrids.
3

Cytology and fertility of viable hybrids of Nicotiana tabacum L. cv. TB-566 with N. alata Link et Otto

86%
Laskowska D., Berbec A.
|
EN
A vigorous hybrid (N. tabacum cv. TB-566 tetra ? N. alata) ? N. alata was obtained by backcrossing a partly viable sesquidiploid hybrid N. tabacum cv. TB-566 tetra ? N. alata to N. alata. The hybrid was a 35-chromosome near-amphihaploid with a pair of N. alata chromosomes in disomic condition. It was completely self- and cross-sterile and formed from 7 to 8 bivalents in pollen mother cells. By using stem pith culture, polyploidized regenerants were obtained from the 35-chromosome hybrid with somatic chromosome numbers from 65 to 70. These regenerants showed fairly regular meiosis with the number of bivalents in pollen mother cells ranging from 27.3 to 30.4. Irregularities in meiosis included a high number of univalents, aberrant tetrads, and a high frequency of micronuclei. The percentage of acetocarmine-stainable pollen ranged from 22.1 to 78.4. A 66-chromosome regenerant showed fairly regular meiosis and was self-fertile but could not be backcrossed to N. tabacum. This barrier seems to be caused by genic imbalance rather than irregularities of meiotic divisions. Hence transfer programs based on the introgression of entire linkage groups (sexual and somatic hybridization) seem to be of little use in the case of that species.
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