Competence for In Vitro Bulblet Regeneration among Eight Lilium Genotypes

Abstract

Competence for in vitro bulblet regeneration was investigated for eight diverse Lilium genotypes (L. `Citronella', L. `Stargazer', L. `Stones', L. `Lovely Girl', L. pumilum, L. lancifolium, L. lancifolium `Orange Star', and L. speciosum var. rubrum). Explants established from bulb scales were cultured on lily bulblet regeneration medium [Murashige and Skoog (1962) modified by reducing the NH4NO3 to 0.825 g·L-1 and KH2PO4 to 0.170 g·L-1, and adding (per liter) 30 g sucrose, 0.1 g myoinositol, 0.4 mg thiamine·HCl, 80 mg adenine sulfate, 16 μm naphthaleneacetic acid, 2 mL·L-1 Plant Preservative Mixture (PPM), and 4.5 g·L-1 AgarGel at pH 5.7] for 8 weeks before transfer to sphagnum peat moss and 4 weeks refrigeration at 5 °C in darkness. All genotypes produced bulblets in vitro. However, the response rate varied among genotypes. Explants of Lilium `Lovely Girl', L. `Citronella', and L. speciosum var. rubrum were most responsive with ≈90% producing bulblets. The number of bulblets per responding explant ranged from 5.2 (`Stones') to 2.3 (L. lancifolium). When comparing in vitro and greenhouse bulblet production, about twice as many bulblets were produced by explants in vitro compared to halved scales incubated in the greenhouse. The percentage of responding explants ranged from 33% to 360% greater for six of the genotypes tested when propagated in vitro compared to bulb scales propagated in the greenhouse. Following refrigeration, bulblets were transferred to the greenhouse for sprouting. Over 80% of bulblets obtained from L. `Citronella', L. lancifolium `Orange Star', L. lancifolium, and L. `Stones' sprouted in the greenhouse. This study illustrates that a diverse range of lily species can be successfully propagated in vitro using a single medium formulation and is the first report of bulblet regeneration in vitro for L. `Citronella', L. `Stones', L. `Lovely Girl', and L. lancifolium `Orange Star'.