The origin of tobacco's T genome is traced to a particular lineage within Nicotiana tomentosiformis (Solanaceae)

Abstract

Nicotiana tabacum (tobacco) is a natural allotetraploid. The maternal genome donor is not controversial and is probably derived from an ancestor of N. sylvestris. The paternal, T-genome donor has been less clear, with N. tomentosiformis, N. otophora, or an introgression hybrid proposed. Here we provide evidence that the T genome of N. tabacum is derived from a particular lineage of N. tomentosiformis. We show that the repetitive sequences of geminiviral origin, GRD53 and GRD3, are present in the genomes of N. tabacum cultivars, a tobacco cell suspension culture TBY-2, and N. tomentosiformis ac. NIC 479/84. Surprisingly, they are not present in another three varieties of N. tomentosiformis. A detailed cytogenetic analysis also revealed that N. tomentosiformis ac. NIC 479/84 most closely resembles the N. tabacum T genome in the location of other tandem repetitive sequences. Thus, tobacco formed after divergence within N. tomentosiformis, and the spectrum of potential donors of the paternal genome can be narrowed to a genotype of N. tomentosiformis characterized by the presence of GRD53 and GRD3 repeats. It is clear that future paternity studies in tobacco should use N. tomentosiformis ac. NIC 479/84 rather than any other accession.