ADVANCES AND STRATEGIES FOR MICROPROPAGATION OF PROTEACEAE SPECIES

Abstract

The objective of this research was to develop in vitro protocols for species of the Proteaceae family. Three model species were selected according to their different growth characteristics: Protea 'Lady Di', Banksia coccinea and Leucospermum 'High Gold'. These three species are considered difficult for vegetative multiplication both ex vitro and in vitro. For Protea 'Lady Di' and Leucospermum 'High Gold' severe pruning was made on stock plants to induce juvenile lateral shoots. The produced buds of Protea were also partially etiolated by different shading systems. Shoots of B. coccinea stock plants were applied with BAP to stimulate the production of lateral shoots in vitro. All the explants were transported in a cooler with their bases in water which demonstrated to be absolutely necessary for the explants to survive in vitro. At the laboratory the explants were defoliated and disinfected using a solution of 5% NaOCl plus nonionic detergent, with different contact times for each species, and two consecutive rinses with distilled sterilised water. The explants were cultivated on MS media supplemented with 30 g L -1 of saccharose and 6 g L -1 of agar, and pH adjusted to 5.7 before sterilisation. The effect of different types and concentrations of plant growth regulators on shoot production, multiplication and induction of adventitious roots were evaluated in L. 'High Gold'. Significant difference was found for the method of partial etiolation in Protea 'Lady Di' depending on the season of the year. In the case of L. 'High Gold' a 90% lateral bud development was recorded when cultivated on a medium supplemented with 1 mg L -1 TDZ. The maximum rate of multiplication for this cultivar was 3.9 compact shoots per explant after four weeks of culture. Shoot elongation of L. 'High Gold' was achieved when explants were subcultured every four weeks on an MS medium supplemented with 1.0 mg L -1 BA for at least four cycles to obtain a rate of multiplication of 2.6. Finally, these buds were cultivated in medium supplemented with different concentrations of IBA (0, 1 and 2 mg L -1 ) to induce adventitious roots, but to date no positive results could be achieved.