Abstract

Fifty six Nicotiana species were used to construct phylogenetic trees and to asses the genetic relationships between them. Genetic distances estimated from RAPD analysis was used to construct phylogenetic trees using Phylogenetic Inference Package (PHYLIP). Since phylogenetic relationships estimated for closely related species are more reliable than that estimated for distantly related species, analyses were conducted separately for groups of taxonomically related species. The results of the present investigation are broadly similar to the inferences by Goodspeed (1954) on the divergence and evolution of Nicotiana species. As would be expected, species included in the same or related subgeneric sections showed greater genetic affinity than species included in distant subgeneric sections.  Available information on the geographical distribution of species, their karyotype differentiation in evolution, genome size variation and chromosome affinity in interspecific hybrids were used to interpret the results. The study has confirmed that the RAPD analysis is suitable for studying phylogenetic relationships between related species.

Key words: Nicotiana, phylogenetic relationship, RAPD.