Establishing tissue culture lines from mature Nuttall’s scrub oak (Quercus dumosa Nutt.) for ex situ conservation
摘要
Quercus dumosa Nutt., a scrub oak native to the coastal sage scrub and chaparral ecosystem of Southern California and Baja California, is endangered, and its remaining populations face many threats. Because technologies do not currently exist to bank Q. dumosa acorns, the species requires alternative strategies for ex situ conservation, such as tissue culture. During initial trials, nodal segment explants created from fresh growth harvested from native populations of mature trees showed necrosis within several days when placed on Woody Plant Medium with 30.0 g L−1 sucrose, 1.0 mg L−1 BAP, and 8.0 g L−1 agar. Explant survival increased steadily through protocol optimization experiments, and, eventually, stable culture lines derived from mature Q. dumosa trees were reliably established and grown. After disinfestation, explants were dried on autoclaved filter paper to remove excess water, sectioned into nodal segments, and then placed on a medium composed of basal salts designed for Q. dumosa, 45.0 g L−1 glucose, 250.0 mg L−1 ascorbic acid, 50.0 mg L−1 phloroglucinol, 100.0 mg L−1 polyvinylpyrrolidone, 100.0 mg L−1 glutathione, 0.33.0 mg L−1 6-benzylaminopurine, and 20.0 µM silver thiosulfate. This medium led to the creation of stable culture lines from 11 of 17 source plants, suggesting that it can be used for the ex situ conservation of Q. dumosa. Additionally, 27 of 34 other species native to the coastal sage scrub ecosystem established at least one culture line on this medium, suggesting that this protocol has utility beyond Q. dumosa.