Molecular comparisons of Salsola tragus from California and Ukraine

In California, the exotic invasive plant Salsola tragus L. (Russian thistle) has been found to consist of two genetic entities, types A and B. Type A, with chromosome number 2n = 36, was identified as S. tragus s.str., but type B, with 2n = 18, was not identical with Salsola species found elsewhere in the world. Plants of S. tragus from Ukraine were subjected to isoenzymic and DNA analyses to determine whether type B was found there and to compare S. tragus from Ukraine with that in California. In isoenzymic assays, plants from Ukraine exhibited patterns of aspartate aminotransferase and 6-phosphogluconate dehydrogenase activity after non-denaturing electrophoresis that were identical with those for S. tragus from California. No Ukrainian accessions had an isoenzymic pattern that resembled type B from California. DNA-based assays, using random amplified polymorphic DNA and inter-simple sequence repeat primers, indicated that all the Ukrainian accessions were similar to S. tragus type A from California and not to Californian type B. The area of origin of type B remains unknown, although it has recently been found to be widespread in southern Africa, where it is also believed to be an introduced species.