Meiosis and fertility in interspecific hybrids of Nicotiana tabacum L. x N-glauca Grah. and their derivatives

Nicotiana glauca is of potential interest to breeders as it carries resistance to black root rot of tobacco. Cytological investigations of sexual interspecific hybrids of N. tabacum T'T'TT (2n = 4x = 48) cv. 'Wislica' x N. glauca GG (2n = 2x = 24) were carried out. The analyses of chromosome association at diakinesis and metaphase I in the PMCs of amphihaploid F-1 T'TG (2n = 3x = 36) revealed low variable pairing with 0-5 bivalents. The sterile amphihaploids F-1 were converted into partial female fertile amphidiploids T'T'TTGG by chromosome doubling. Among 36 mature plants obtained, 15 were found to have chromosome numbers (2n = 6x = 72) and were verified as amphidiploids, 9 had (2n = 6x = 70 or 71) chromosomes while the remaining 12 were haploid. True amphidiploids, in spite of quite high chromosome pairing during meiosis, were very different in pollen fertility, ranging from 0% to 85%. Male fertility disturbances did not correlate with the degree of female fertility upon pollination with N. tabacum. Sesquidiploids T'TG (2n = 5x 60) obtained from backcrossing the amphidiploids to parental tobacco showed more than 22 bivalents, 10-12 univalents and occasional multivalents that indicated the possibility of interchange events between N. tabacum and N. glauca genomes.