The Development of a Micropropagation Protocol Suitable for a Wide Range of Quercus dumosa Genotypes for Ex Situ Conservation

Quercus dumosa, or Nuttall’s scrub oak, is endangered due to human encroachment, misidentification, disease, and wildfire. Micropropagation is a method of ex situ conservation in which plants maybe be preserved under aseptic conditions away from the many threats they face. However, each genotype grows differently; what may encourage growth in one individual may prove lethal for another. Shoots extracted from in vitro-germinated acorns grew on tissue culture medium composed of Woody Plant Medium salts and vitamins, 3% sucrose, 2 mg L-1 6-benzylaminopurine, and 8 g L-1 agar. Two distinct groups became apparent: high-growth genotypes that could be easily multiplied with basic protocols and low-growth genotypes that struggled to remain alive. A total of 16 high-growth genotypes served to identify common factors that either improved or diminished growth potential so that low-growth genotypes may be grown more reliably. The addition of 200 mg L-1 ascorbic acid decreased culture mortality in all tested genotypes without reducing growth potential, but 2.5 g L-1 activated charcoal, another antioxidant, led to reduced mortality and near cessation of growth in all tested genotypes. A combination of 0.5 g L-1 ascorbic acid, 5 uM sodium nitroprusside, 1.25 uM gibberellic acid, 1 mg L-1 6-benzylaminopurine, 0.125 mg L-1 indole-3-butyric acid, 0.5 mM gamma-aminobutyric acid, and 5 mg L-1 adenine sulfate led to increased growth across the majority of fast-growing genotypes and all tested slow-growing genotypes. Additionally, replacing sucrose with glucose has significantly decreased necrosis and increased culture growth across all tested genotypes in an ongoing experiment.