Abstract
Through interspecific hybridisation, two new amphiploids with high chromosome numbers were obtained in the crosses N. velutina (n=16)×N. amplexicaulis (n=18) and N. occidentalis (n=21)×N. amplexicaulis (n=18). They were grown through five generations and found to be extremely stable, completely fertile and most vigorous in growth. A nulli-amphiploid in the cross N. occidentalis×N. amplexicaulis with chromosome number 2n=76, derived through a loss of pair of chromosomes from the full amphiploid was also established as a stable hybrid. Chromosome pairing in the hybrids was regular and complete. In the first cross the chromosome configuration was 34 bivalents. In the second, the configuration was 39 bivalents in the amphiploid and 38 in the nulliamphiploid.
