Systematics Section / ASPT
Chase, Mark W. , Clarkson, James J. , Knapp, Sandra .
Origins of allotetraploids in Nictoiana (Solanaceae): evidence from glutamine synthase.
In Nicotiana (Solanaceae), approximately 40% of the 76 species are allotetraploid, and sorting out the parentage of some of these species groups has been difficult. In the past, we have used analyses of plastid DNA and nuclear ribosomal ITS sequences, but neither of these kinds of sequences can reliably reveal both parents. The problem has been compounded by the fact that some groups of species are old tetraploids that have undergone a phyletic radiation and diverged molecularly from the parental lineages, which themselves have also speciated since the time of synthesis. Here we report on efforts to use a low-copy nuclear DNA region, plastid-expressed (ncpGS) glutamine synthase, to sort of out evolutionary history of allotetraploids. Sequences from the allotetraploids can be extremely similar to extant diploids, indicating that the hybrids are recent, (e.g. N. tabacum) or highly divergent from all extant diploids, representing ancestral forms (e.g. the progenitors of N. section Suaveolentes). Nicotiana tabacum produces two types of sequences that correspond closely to the known parental species, N. sylvestris and N. tomentosiformis. Other recently formed allotetraploids are similarly easily identified, but older groups of allotetraploids, such as N. section Suaveolentes (25 species from Australia and one from Africa) have two kinds of sequences that do not match any extant diploid section, thus making it more difficult to understand their origins.
1 - Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, UK
2 - Natural History Museum, Department of Botany, Cromwell Road, London, SW7 5BD, United Kingdom
Presentation Type: Paper
Location: Cottonwood B (Snowbird Center)
Date: Tuesday, August 3rd, 2004
Time: 4:30 PM