Rhizobial diversity and function in rooibos (Aspalathus linearis) and honeybush (Cyclopia spp.) plants: A review

Aspalathus linearis (rooibos) and Cyclopia spp. (honeybush) are leguminous plants endemic to the fynbos region of South Africa. These plants have become popular for their use as herbal teas and thrive in the acidic, nutrient poor soils of the fynbos region. Plants in this region rely on rhizobia to fix nitrogen and supply them with other important nutrients such as phosphorous, in exchange for a carbon source. This review focuses on the species diversity of rhizobia associated with A. linearis and Cyclopia spp. plants. Genera that are regularly isolated from rooibos and honeybush root nodules include Rhizobium, Burkholderia, Mesorhizobium and Bradyrhizobium. These species produce bioactive compounds that directly or indirectly affect growth of leguminous plants.