The in vitro induction of adventitious shoot and root apices on Narcissus (daffodil and narcissus) cultivar tissue

Abstract

A new technique is reported here for the rapid propagation of Narcissus cultivars involving the induction of shoot and root apices from small pieces of leaf base tissue, inverted scape sections, and from ovaries, in axenic culture. Shoot and root apices were obtained on the above explants of all nine Narcissus cultivars tested. The optimal medium contained modified Murashige and Skoog (1962) inorganic salts, the organic constituents recommended by Ziv et al. (1970), and higher-than-normal growth regulator levels. Proliferating shoot apices were induced on a medium containing 4.4 × 10−5 M (10 mg/litre) 6-benzylaminopurine (BAP) and 5.3 × 10−6 M (1 mg/litre) naphthaleneacetic acid (NAA). Plantlets grew optimally if transferred to a medium containing 9.0 × 10−6 M (2 mg/litre) BAP and 2.0 × 10−7 M (2 mg/litre) NAA. The induction of roots on plantlets grown in vitro required a half-strength salt and sucrose solution without growth regulators.In 5 months, 2620 plantlets were produced from two leaf base explants. This technique is considerably more efficient than any known conventional methods of propagating Narcissus.Root apices were optimally produced on a medium containing 2.0 × 10−6 (0.5 mg/litre) to 2.0 × 10−5 M (4 mg/litre) BAP and 1.0 × 10−4 (20 mg/litre) to 2.0 × 10−5 (4 mg/litre) NAA. Callus was induced on leaf base explants, inverted scape sections, and on ovaries; the ovary expiants required the highest levels of auxin for the induction of callus and were most responsive. Thus, the levels of growth regulators required to induce a response in vitro are higher than so far reported for plants that have been propagated by tissue culture.Although the levels of various growth regulators used were found to be important in obtaining apices, the relative ratio of cytokinin to auxin was also found to be critical. Although considerable differences in clonal responsiveness were noted, cultures were obtained from all nine Narcissus cultivars tested.The induction of adventitious meristems of leaf base explants is a particularly promising method for the propagation of virus-free material and for the rapid propagation of valuable horticultural material.