|Authors: ||I. Kovalchuk, T. Turdiev, Z. Mukhitdinova, S. Frolov, B.M. Reed, G. Kairova|
|Keywords: ||apple, cryoprotectants, germplasm preservation, natural moisture content, sweet cherry, tart cherry|
Cryopreservation of dormant buds of temperate trees in liquid nitrogen can provide a safe backup of field germplasm collections.
Cryopreservation at the natural moisture content (MC) would greatly accelerate the storage process.
This study examined the effect of cold acclimation, moisture content and cryoprotectants on the viability of dormant buds after liquid nitrogen (LN) exposure by staining with 2, 3, 5-Triphenyltetrazolium chloride (TTC). All natural MC buds (40 to 55% MC), both cold acclimatized (CA) for one week and or non-CA buds, died after LN exposure.
Post-LN viability of CA 30% MC bud segments was 66-100%. Viability was 100% for the 30% MC bud segments with either standard CA for one week, or cooling 2°C/min to -30°C before LN exposure.
For CA natural MC buds, six pretreatment and cryoprotectant combinations were tested with controlled cooling 2°C/min to -30°C before LN exposure.
With this technique, viability for tart cherry was 100% for bud segments with natural MC with a 3-h pretreatment and cryoprotection with PVS2, PGD or honey; and for sweet cherry with PVS2, PVS3, PGD, honey + 15% DMSO, or IPBB-1 (50% glycerol and 50% glucose). For apple buds IPBB-1 gave 100% viability for all and PVS2 was 100% for most genotypes.
Results for in vitro and grafting recovery after PVS2 treatment and LN exposure were 10 to 23% lower than the TTC results for the three genotypes tested (77-90%). Using these pretreatments and cryoprotectants with a programmable freezer reduced the time required to store dormant buds from nearly two months to one week.
Further studies are planned to determine viability of grafted or in vitro-recovered buds following the best procedures.
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