Ex-Situ Oak Conservation with Improved Tissue Culture Initiation

Megan Philpott, Aislyn Tyler, Mairead Kennedy, and Valerie Pence

Published May 2026 in International Oaks No. 37: 357–364

Abstract

The development of tissue culture propagation protocols is of vital importance for oak species, as micropropagation can be used to clone valuable specimens, propagate rare species for restorations, and produce propagules for long-term storage in cryopreservation. However, oak species are widely considered to be difficult to propagate in vitro, with issues such as fungal and/or bacterial contamination often hindering efforts. Using new growth collected from six rare oak species and two common oak species, we tested two different anti-microbial media and six different sterilization methods to reduce contamination in the initiation of new shoot cultures. The use of medium supplemented with the fungicide benomyl was compared to a medium supplemented with commercially available Plant Preservative Mixture (PPM™), with the benomyl medium significantly reducing the fungal contamination rate, while PPM™ significantly reduced the bacterial contamination rate. The addition of a 2-min rinse in a benomyl and antibacterial solution after sterilization in commercial bleach, followed by a rinse in sterile water to reduce benomyl toxicity, resulted in significantly lower fungal and bacterial contamination, and adoption of this general procedure reduced the fungal contamination rate by 34% and the bacterial contamination rate by 45% from year one of the study to year three. While both species and genotype are unavoidable factors that have a significant influence on the contamination rate, the adoption of enhanced sterilization procedures can lead to greater efficiency and success in the conservation of oak species.

Keywords

micropropagation, in vitro, fungus, bacteria, sterilization

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