This work was designed to study the taxonomic characters of some Solanum species in Saudi Arabia, as well as to find out the genetic distances and characterize some molecular genetic markers specific to different Solanum species. This was achieved through the investigation of the morphology, seed storage proteins, isozymes and DNA attributes of Solanum collected from five different areas in Aseer region, south west of Saudi Arabia (Wadi El-Dawaser, Abha, Najran, Jazan and Bisha). Thirteen taxa representing six different species of Solanum (S. torvum, S. dulcamara, S. villosum, S. nigrum, S. incanum and S. sisymibriifolium) were collected and morphologically described. These taxa were differentially distributed across the areas of study from very common, common, present and absent. Six out of nine qualitative morphological characters were polymorphic among the thirteen Solanum taxa, reflecting the difficulty to choose the most informative morphological characters. Total protein content in dry seeds of different Solanum taxa were extracted and analyzed using SDS-PAGE. Alchol dehydrogenase (ADH) and malate dehydrogenase (MDH) isozymes were extracted and detected on non-denatured polyacrylamide gels. Twenty one polymorphic protein bands out of thirty five were scored. ADH isozyme showed low level of variation with four polymorphic..