Rapid in vitro Propagation of Virus-Indexed Freesia
An efficient tissue culture method has been developed for the production of more than 50,000 virus-free gladiolus transplants within 30 weeks [A.E. Logan and F.W. Zettler (1984) Acta Horticulturae (in press)]. This method has been used, with modifications, to successfully establish a rapid in vitro propagation system for virus-indexed freesia (Freesia refracta). Using Freesia refracta cvs. Ballerina and Rose Marie, apical shoot-tips (0.5 to 0.7 mm) were established (Stage I) on an agar medium containing Murashige and Skoog salts, 2.0 mg/1 kinetin, and 0.1 mg/1 naphthaleneacetic acid (NAA). Plantlets were transferred to a similar medium containing 4.0 mg/1 kinetin and no auxin 6 to 7 weeks later for shoot proliferation (Stage II). Plantlets were subcultured on Stage II medium every 4 to 5 weeks as needed and yielded approximately 12 axillary shoots per culture. Roots developed readily in this medium suggesting that it may not be necessary to transfer the shoots to a specific root-inducing medium as is the case with gladioli. Virus indexing was accomplished using several methods, including electron microscopy and enzyme-linked immunosorbent assay.