Articles
Elm genetic resources conservation in Finland supplemented by dormant bud cryopreservation
Article number
1421_15
Pages
111 – 116
Language
English
Abstract
Ulmus laevis (Pall.) and Ulmus glabra (Huds.) are endangered and protected species in Finland.
Elms are globally threatened by the Dutch elm disease which is likely to spread also to Finland in the future.
The genetic diversity of elms in Finland is conserved in dynamic ex situ collections which have grafted material originating from the small and scattered Finnish elm populations.
These collections can produce more diverse seed than the natural populations, which sometimes consist of only a few trees.
Increased use of elm seed of native origin for landscaping and forest regeneration could support conservation of elms, but is, paradoxically, complicated by interpretation of the protection status.
To prevent the loss of trees in conservation collections to Dutch elm disease or other hazards, cryopreservation and tissue culture methods were developed and tested for U. laevis and U. glabra dormant buds.
The buds were collected in winter, frozen using a programmable freezer at the rate of -0.17°C min‑1 to -38°C and plunged into liquid nitrogen.
For U. laevis 50 and 63% of the cryopreserved dormant buds were recovered in two test thawings through tissue culture.
However, for U. glabra, the proportion of successful tissue culture initiations was considerably lower, at 6 and 13%. This was both due to decreased bud viability after cryopreservation and higher contamination rate.
However, dehydrating U. glabra buds from initial average 52% moisture to 32% improved the post-thaw viability and reduced the contamination rate so that 43% of the dehydrated buds were recovered instead of 11% of buds frozen without dehydration.
Even though cryopreservation itself does not solve the of susceptibility of the material to Dutch elm disease, most genotypes can now be recovered from cryostorage if lost from the collections.
Elms are globally threatened by the Dutch elm disease which is likely to spread also to Finland in the future.
The genetic diversity of elms in Finland is conserved in dynamic ex situ collections which have grafted material originating from the small and scattered Finnish elm populations.
These collections can produce more diverse seed than the natural populations, which sometimes consist of only a few trees.
Increased use of elm seed of native origin for landscaping and forest regeneration could support conservation of elms, but is, paradoxically, complicated by interpretation of the protection status.
To prevent the loss of trees in conservation collections to Dutch elm disease or other hazards, cryopreservation and tissue culture methods were developed and tested for U. laevis and U. glabra dormant buds.
The buds were collected in winter, frozen using a programmable freezer at the rate of -0.17°C min‑1 to -38°C and plunged into liquid nitrogen.
For U. laevis 50 and 63% of the cryopreserved dormant buds were recovered in two test thawings through tissue culture.
However, for U. glabra, the proportion of successful tissue culture initiations was considerably lower, at 6 and 13%. This was both due to decreased bud viability after cryopreservation and higher contamination rate.
However, dehydrating U. glabra buds from initial average 52% moisture to 32% improved the post-thaw viability and reduced the contamination rate so that 43% of the dehydrated buds were recovered instead of 11% of buds frozen without dehydration.
Even though cryopreservation itself does not solve the of susceptibility of the material to Dutch elm disease, most genotypes can now be recovered from cryostorage if lost from the collections.
Authors
S. Välimäki, L. Yrjänä, T. Aronen, M. Rusanen
Keywords
Ulmus laevis, Ulmus glabra, ex situ conservation, slow cooling, tissue culture, organogenesis
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