The South African Hordeum capense is more closely related to some American Hordeum species than to the European Hordeum secalinum: a perspective based on the 5S DNA units (Triticeae: Poaceae)

Abstract

Several authors have proposed that the European Hordeum secalinum and the morphologically similar South African Hordeum capense are conspecific. In this paper we provide evidence that the two species differ in their 5S DNA unit class composition. We also report on the diversity of 5S DNA units in Hordeum muticum, a South American species. When the 5S rDNA unit class composition for these three species is compared with the unit class composition for all Hordeum species thus far investigated, it appears that H. capense is more closely related to the American Hordeum species containing the long Y2 unit class, than to H. secalinum, which lacks the long Y2 unit class but contains the long X2 unit class found in H. marinum. This analysis suggests H. capense may have originated from a stock common to the South American species, such as H. muticum.Key words: 5S DNA unit class, Hordeum capense, Hordeum secalinum, Hordeum muticum, continental drift.