Cytology and fertility of amphidiploid hybrids between Nicotiana wuttkei Clarkson et Symon and N. tabacum L.

In this study, the morphology, cytology and crossability of amphidiploid hybrids (2n = 8x = 80; WWW′W′TTT′T′) between Nicotiana wuttkei × Nicotiana tabacum were studied. An R1 progeny of the hybrids were produced through in vitro chromosome doubling of the N. wuttkei × N. tabacum cv. Wiślica amphihaploids. The resulting amphidiploids showed enough self-fertility to be perpetuated by self-pollination. The plants preserved their phenotypes and the number of chromosomes over subsequent R2–R4 selfed generations. During metaphase I the bivalent number increased progressively over the generations R1 to R4 and averaged 36.9, 37.4, 38.6 and 38.7, respectively. In addition, a progressive increase in pollen viability was observed: 50.8, 55.5, 62.3 and 65.7 % in generations from R1 to R4, respectively. Genomic in situ hybridization of R4 plants revealed recombination between the parental species on two chromosomes. Reciprocal crosses of R2 generation amphidiploids to N. tabacum cv. Wiślica yielded sesquidiploid hybrids (2n = 6x = 64; WW′TTT′T′). When N. tabacum cv. Wiślica is the pollinator, the amphidiploid gave rise to a total of 25 sesquidiploid plants with the cytoplasmic genome of N. wuttkei, while the reverse mating resulted in a mixed population consisting of a single sesquidiploid plant with the cytoplasm of N. tabacum and 203 plants of supposedly maternal origin. Our amphidiploid N. wuttkei × N. tabacum cv. Wiślica can be concluded as sufficiently stable and is regarded as a new artificial hybrid species.