A method for the initiation of callus capable of plant regeneration from in vivo grown cormels of gladiolus (Gladiolus x grandiflorus Hort.) is described. Sliced cormels of the large-flowering hybrid, 'Peter Pears' were cultured in vitro on a modified Murashige and Skoog medium, supplemented with various auxins. Yellow callus, which was either friable or compact, could be induced on all media tested. Callus induced on media with naphthaleneacetic acid failed to proliferate. Callus induced on media with 9 mM 2,4-dichlorophenoxyacetic acid showed the best growth. Addition of micro-elements and vitamins increased the induction and growth of callus capable of plant regeneration. Explants taken from the middle part of the cormels had the highest competence for callus initiation. Callus was induced on several gladiolus hybrids and the South African species G. garnieriiKlatt. Callus induction was genotype dependent and among the cultivars tested, 'Peter Pears' and 'White Prosperity' were superior with respect to callus production on the media with either 2,4-dichloropbenoxyacetic acid or picloram. Plants were regenerated from yellow compact callus of all genotypes on media containing zeatin and benzyladenine in various concentrations.
Abbreviations: 2,4-D -2,4-dichlorophenoxyacetic acid, MS -Murashige and Skoog basal salt and vitamins (1962), CI -callus induction medium, NAA -a-naphthaleneacetic acid, 5,yridinecarboxylic acid, purine Variables Percent total callus * Percent compact or friable callus * Percent friable callus * Apical slices of cormels 100 4-0.0 56 4-9.9 8 4-5.8 Central slices of cormels 100 4-0.0 68 4-9.3 12 4-9.9 Basal slices of cormels 20 4-4.1 12 4-6.5 8 4-5.8 Apical slices of cormlets 100 5:0.0 52 4-7.1 16 4-6.5 Central slices of cormlets 100 4-0.0 92 4-3.9 76 4-7.6 Basal slices of cormlets 80 4-0.1 28 4-6.4 12 4-5.8 Central slices -6 months 76 4-8.5 56 5:9.9 3 4-6.5 Central slices -9 months 60 4-9.8 44 5:9.9 8 :k 9.3 Central slices -12 months 8 4-5.4 8 4-5.4 0 4-0.0 * Values 4-standard error. types readily p r o d u c e d regenerable callus. M e d i u m CI