Improving culture initiation of mature oak shoots through use of silver thiosulfate

Abstract

Premise Of the approximately 430 species of oaks ( Quercus spp.) that have been assessed, 31% are threatened with extinction and in need of safeguarding. However, oak seeds cannot be seed banked, and thus rely on alternative strategies such as in vitro culture for ex situ conservation. One challenge to this approach is low culture initiation rates. Our objective was to identify factors that may improve the establishment of shoot cultures in vitro using new growth collected from mature trees. Methods Shoot cuttings were harvested from individuals of five different oak species ( Q. alba , Q. bicolor , Q. macrocarpa , Q. muehlenbergii , and Q. palustris ). Shoots were cultured onto medium with or without 50 µM silver thiosulfate (STS), a known inhibitor of the stress hormone ethylene. Cultures were grown for one month, at which point shoots were assessed for survival. Results Shoot survival was significantly greater in shoots cultured on medium containing STS compared to the control group, with the overall survival rate increasing from 65% to 73%. Discussion Increasing the survival rate of newly established cultures is important in ensuring that material collected from endangered species has the best chance for survival, which is critical for successful ex situ conservation.

Harnessing the power of botanical gardens: Evaluating the costs and resources needed for exceptional plant conservation

“…This likely reflects the fact that many Asteraceae species have been successfully propagated in vitro (Abraham and Thomas, 2016 ), suggesting that a number of these species adapt well to in vitro manipulation. However, although the initiation of cultures of several Quercus L. species has been reported (Ballesteros and Pritchard, 2020 ), oaks are known to be difficult to initiate in vitro and the rates of initiation are often low (Kramer and Pence, 2012 ; Brennan et al, 2017 ; Winkeljohn et al, 2022 ). This is reflected in the higher cost per point ($43,530) in a project dealing with Q. dumosa Nutt.…”

Building capacity in the conservation of exceptional plant species

“…For tissues that must be propagated in vitro, such as clonal shoots, initiation into tissue culture can be a major bottleneck to creating an in vitro collection. Winkeljohn et al ( 2022 ) explore this issue in five species of Quercus L., using a known ethylene inhibitor in the initiation medium to improve initiation rates. Another challenge to establishing and growing in vitro tissues is their susceptibility to contamination by bacteria and fungi.…”