Cold acclimation and cryopreservation of 'MM106' apple cultures
Date
1989-04
Authors
Journal Title
Journal ISSN
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Publisher
ORCID
Type
Degree Level
Masters
Abstract
Germplasm apple orchards are in danger of depletion and
are often inaccessible due to land expropriation and political
constraints. Since micropropagative methods are available
for most apple cultivars and since methods of cryopreservation
for some have been developed, this study was instigated
to cryopreserve in vitro shoots to broaden the
scope of technology available for conserving genetic resources.
In vitro shoots of Malus domestica Borkh. cv 'MM106' were
cold hardened to -19ºC in a simulation of autumnal hardening. When shoot-tips were excised from these cold-hardened
cultures, and cryoprotected with 5% dimethylsulfoxide (DMSO)
+ 18.2% D-sorbitol, 60% of the shoot-tips survived freezing
to -34°C. When cold-hardened shoots ( LT₅₀ of -19°C ) were
incubated for an additional 7 days on MS media that contained
5 ppm of abscisic acid (ABA), the shoot-tips gained 7.5°
cold resistance, but cold resistance was lost by longer incubation
on media that contained ABA.
Unhardened in vitro apple shots were severely damaged
by preculturing on media with 5% DMSO + 5% glucose. The cold hardiness of unhardened shoots was unaffected by a
3 week incubation at 25°C on media that contained 5 to 50
ppm of ABA.
Most shoot-tips and meristems, excised from cold hardened
cultures, were consistently recovered only as callus, despite the use of different sized explants with several cryoprotectants and different freezing and thawing rates.
More explants produced callus at -30 than at -40ºC. Less
than 35% of explants produced callus after removal from liquid
nitrogen. None of callused explants produced shoots.
In this study, in vitro shoots of a woody species
cold acclimated in response to a simulation of autumnal hardening, but the length of the hardening regime did not affect
the level of cold hardiness. The shoots gained additional
hardiness by a 7 day exposure to 5 ppm ABA. ABA did
not become effective until after the 'MM106' apple shoots
had been exposed to a cold-hardening regime.
Description
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Citation
Degree
Master of Science (M.Sc.)
Department
Horticulture
Program
Horticulture