Canadian Forest Service Publications

In vitro germination protocol for the propagation of the endangered butternut tree (Juglans cinerea L.). 2019. Williams, Martin; Forbes,Kathleen; Williams, Charlene; and Beardmore, Tannis. Native Plants Journal, Volume 20, Number 2, Summer 2019 Pages 117-121.

Year: 2019

Available from: Atlantic Forestry Centre

Catalog ID: 39892

Language: English

CFS Availability: PDF (request by e-mail)

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Abstract

Butternut (Juglans cinerea L. [Juglandaceae]) is a native tree in the US and Canada that is in rapid decline due to an introduced fungal pathogen (Ophiognomonia clavigignenti juglandacearum [Oc-j]). Resistance to the disease has not been identified, and conservation efforts for this nut-producing species have concentrated on the ex situ cryogenic storage of germplasm. The conventional method for growing butternut uses the nut. In general, Juglans species exhibit seed dormancy, which can be broken by cold, moist stratification at 1–4 °C (32–39.2 °F) for 90–120 d. Stratified nuts usually germinate within 4 wk, with variation among seeds. Average germination by the conventional method is approximately 60% for J. cinerea. A new in vitro germination protocol has been developed for the production of butternut seedlings that results in high germination and acclimatization success (conversion of germinants growing on medium to seedlings growing in soil) for both cryogenically and non-cryogenically stored embryonic axes (root–shoot axis). This protocol eliminates the need for conventional nut stratification; produces decontaminated tissue via surface sterilization, such that seedlings are visibly canker-free; increases germination; and enables long-term cryogenic storage.

Plain Language Summary

Butternut (Juglans cinerea), a tree native to the USA and Canada, is endangered by a nonnative fungal pathogen (Ophiognomonia clavigignenti-juglandacearum). The disease resulting from this pathogen is rapidly affecting tree survival and the availability of nuts for recruitment in their habitat and also for stakeholders involved in growing butternut commercially or for conservation purposes. Conventionally, nuts are the propagation method of choice by nursery growers, butt nut availability and potential nut contamination by the pathogen are making it more difficult for growers to produce seedlings from appropriate seed zones. To overcome some of these issues, we have developed a novel tissue culture method to grow butternut seedlings, producing canker-free seedlings with high germination and acclimatization efficiency. This method also has the added benefit of being able to directly use or cryogenically store the nuts for the long term, which is highly valuable for the conservation of the species.