GENERATION OF A FRAMEWORK PHYSICAL MAP FOR TOBACCO.

¹ NC State University, Department of Plant Pathology, Campus Box 7616, Raleigh NC 27695

² NC State University, Department of Horticultural Science, Campus Box 8619, Raleigh NC 27695

Cultivated tobacco, Nicotiana tabacum is member of the Solanaceae family, which also includes eggplant, pepper, petunia, potato, and tomato. N. tabacum is an amphiploid species (2n=48) likely resulting from an interspecific cross between N. sylvestris (2n=24) and N. tomentosiformis (2n=24). N. tabacum has a very large genome compared with other cultivated solanaceous plants. At approximately 4.5 billion base pairs, it is 1.5 times the size of the human genome. As part of the Tobacco Genome Initiative, we are employing a combination of strategies to identify and localize a large percentage of genes in N. tabacum. Due to the large genome size, standard BAC by BAC and shotgun sequencing methods are labor-intensive, time-consuming and not cost effective. We are combining a methyl filtration approach with standard EST sequencing to identify gene tags in N. tabacum. In order to map these gene tags to gene-rich regions, we are developing a framework physical map of the tobacco genome using a novel approach that combines multiple restriction digestion of BACs followed by four-color labeling of the resulting fragments, and visualization with an automated sequencer. Mapping analysis is underway, and preliminary results are presented.