Genotype-specific requirements for in vitro culture initiation and multiplication of Magnolia taxa

The influence of basal media composition, concentration of plant growth regulators (PGRs), and the developmental stage of primary explants (dormancy, stage of bud opening and fruit ripening) on the initiation phase of nine Magnolia genotypes, including M. stellata /Sieb. & Zucc./Maxim., M. × soulangeana ‘Rustica Rubra’, M. denudata Desr., M. × soulangeana ‘Alexandrina’, M. liliiflora Desr., M. officinalis var. biloba Rehd. & Wils., M. salicifolia Maxim., M. × soulangeana ‘Lennei’, and M. kobus DC, was evaluated. The highest efficiency of primary culture initiation of seven Magnolia genotypes (except for M. liliiflora and M. salicifolia) was achieved from primary explants collected in the bud opening stage. A high positive correlation was found between total tannins and efficiency of the primary culture initiation at the fruit ripening stage (r = 0.833). Standardi and Catalano medium (S₂) with 0.5 mg l⁻¹ of 6-benzylaminopurine (BAP) was the most appropriate for multiplication of M. × soulangeana ‘Alexandrina’, whereas tissue cultures of M. × soulangeana ‘Lennei’ proliferated and grew better on S₂ medium with 1.0 mg l⁻¹ of BAP and 1.0 g l⁻¹ of polyvinylpyrrolidone. The requirements for the composition of basal media and concentration of PGRs in the initiation and multiplication stages of micropropagation of various Magnolia species and cultivars are genotype-specific.