In Vitro propagation of cineraria (Senecio cruentus DC.) by shoot tip culture

Cineraria (Senecio cruentus DC.) shoot tips were grown and multiplied in vitro on Murashige and Skoog medium (1962) and on the modified Murashige and Skoog medium (1974) containing lAA, kinetin, and organic supplements. Explants were isolated in culture from plants grown from seeds germinated in vitro. Germinated seeds produced cotyledons heavily covered with colored trichomes. The early detection of the intensity of flower color was predictable in accordance with color of trichomes on cotyledons. Formation of single or multiple shoots, plantlets, leafy callus and roots depended on the hormone levels and organic constituents used. Shoots cultured on a medium with a high kinetin to auxin ratio produced shoots; whereas, the addition of only an auxin to the medium produced roots and complete plants which could later be transferred to the greenhouse.

The greatest number of shoots per excised shoot tip was obtained when the MS medium was supplemented with adenine sulfate and L-tyrosine, especially when added to the modified MS medium with half the recommended concentration of macroelements. The addition of casein hydrolysate in the MS medium caused shoot suppression and broad thick leaves. Exogenous auxin was not a critical additive to any multiplication media, since shoot tip explants developed plants without an lAA supplement. Shoots originated form axillary and adventitious buds. Root formation was best on the MS medium containing the supplement casein hydrolysate and half the recommended concentrations of macroelements. Adventitious root growth increased with increasing NAA concentrations in the medium. The addition of adenine sulfate and L-tyrosine to a modified MS medium caused a decrease in frequency of rooted plantlets. The shoots tended to form stubby to no roots with a large percent of callus on the modified MS medium. Rooted shoots grew into normal plants and subsequently flowered after a 23 week period from in vitro culture to greenhouse. Growth habits and bloom characteristics of plants originated in vitro or in a greenhouse were similar.