In vitro propagation of Cotula bipinnata Thunb. and Chironia linoides L., South African ornamental species suitable for cultivation in Mediterranean area

Among the five geographical areas in the world characterized by the Mediterranean-type climate, the Cape region in South Africa is particularly rich in biodiversity. This leads to the consideration that the offer of new ornamentals can be enlarged through the introduction of South-African species. In this paper, two species, a herbaceous, Cotula bipinnata Thunb. and a shrub, Chironia linoides L. have been selected for their ornamental characters to explore the suitability of cultivation in the Mediterranean area of the northern hemisphere. Studies to verify the attitude to in vitro propagation have been carried out to provide homogeneous selected material for fast delivery to the market. Three cytokinins (6-benzyladenine (BA), 2-isopentenyladenine (2-iP), meta-topolin (mT)) at two concentrations (0.15-0.3 mg 
L^-1) were added to MS salts and vitamins and the shoot growth was compared against the Plant Growth Regulators (PGR)-free control medium. The plantlets were then transferred into the greenhouse for acclimatization under a mist system. Chironia cultures on MS+BA at 0.3 mg L^-1 showed the highest multiplication rate, but poor quality with chlorosis and hyperhydricity appearance. The use of 2-iP at low concentration induced a high multiplication; a good shoot quality was obtained when both 2-iP and mT were used as growth regulators. Although 2-iP had a stimulatory effect on root development, the best rooting performance was achieved culturing shoots on media lacking PGRs. Cotula shoots on MS + mT highlighted the best multiplication rate; 2-iP at low concentration allowed to get the highest shoots, a good multiplication rate and plant material of good quality. The best rooting percentage was achieved in absence of PGR. The plantlets of Cotula, grown in medium containing 2-iP, showed root development and excellent survival after transfer to the greenhouse, while those of Chironia, despite the good behaviour at the end of the vitro culture, showed a low acclimatization percentage.