Chromosomal rearrangements in interspecific hybrids between Nicotiana gossei Domin and N-tabacum L., obtained by crossing with pollen exposed to helium ion beams or gamma-rays

it is very difficult to obtain interspecific hybrids between Nicotiana tabacum L. (2n = 48) and N. gossei Domin (2n = 36), because of strong cross incompatibility. We had already obtained interspecific hybrids between these two species, crossing N. gossei flower with N. tabacum pollen exposed to He ions or gamma-rays. Here, we analyze chromosome constitution of these hybrids by genomic in situ hybridization. In root tip cells of the two hybrids obtained with He ion exposure, most mitotic cells contained 18 chromosomes of N. gossei and 24 chromosomes of N. tabacum. However, in some cells, translocations and insertions between parental genomes were observed. On the other hand, in a hybrid obtained by gamma-ray irradiation, intergenomic rearrangements were not observed, although mitotic cells showed 19 hybridization signals with N. gossei DNA in 41 chromosomes. Such chromosomal changes in structure or constitution may be related to overcoming cross incompatibility between these two species. (C) 2003 Elsevier Science B.V. All rights reserved.