Disinfestation methods and media components affect tissue culture of the geophytic species Schoenocaulon officinale ( Melanthiaceae )

Schoenocaulon officinale, sabadilla, is an herbaceous perennial geophyte native to Mexico, Central America, and Venezuela. Its underground storage organ is a tunicate bulb with a long juvenile (vegetative) period which complicates breeding with a long generation time (1.5-3 years) from seed to flowering. Seeds contain alkaloids useful as green pesticides. Current seed production is wild harvested, threatening species integrity and longevity. As part of crop domestication, tissue culture of selected early-flowering and high alkaloid-producing clones is a primary goal. Bulb divisions of mature plants do not re-establish; classic bulb propagation methods are ineffective in daughter bulb production. The objectives of this research are to study the effects of disinfestation and media components in establishing sterile, in vitro cultures. To achieve those objectives 2 experiments were carried on. Expt. 1: Mature bulbs (n=10 genotypes; n=21 bulbs; year 1) were stored at 4°C for 4 weeks; leaves, roots, sheath and outer tunics were removed; rinsed in sterile DI water, surface-sterilized in 70% EtOH and 0.0825% sodium hypochlorite. Explants (n=72) were split at the basal plate into wedge-shaped pieces with >3 scales, grown at 20C in Murashige and Skoog (MS) medium (pH=5.7) plus 5.18 mg BA L^-1 (6-benzylaminopurine), 3% sucrose and 0.7% agar. In year 2, due to high % bacterial contamination, explants were subcultured onto MS callus media with 1 mg L^-1 BA, 2.5 mg L^-1 IBA, followed by 2 g L^-1 activated charcoal, 100 mg L^-1 citric acid, and 150 mg L^-1 ascorbic acid to prevent oxidation. Four months later, 3.5% of explants initiated roots while 1.75% formed callus; subcultured calli formed shoots after 3-4 weeks. Expt. 2: 12 genotypes were cultured on MS medium plus an antibiotic to suppress bacterial growth; 75% had bacterial contamination >4-5 days and 100% >2 weeks with browning (oxidation of phenolic exudates) leading to cellular necrosis. Future research will focus on potential endophyte involvement in browning and tissue senescence.