The differential expression of six basic helix-loop-helix (bHLH) genes in response to low temperatures was studied by evaluating their mRNA levels in the buds and shoots of grapevines. Comparison of the amino acid sequences deduced from nucleotide sequences of the bHLH genes in Vitis labruscana transcripts revealed homologies ranging from 58.8% (VlCEbHLH1 and VlCEbHLH4) to 8.2% (VvbHLH and VlCEbHLH3). Specific primers from unique regions of genes were obtained by alignment of nucleotide sequences and used to evaluate differential expression patterns of bHLH genes. The accumulation patterns of bHLH mRNAs were induced differentially and dependent on the treated temperatures, −20°C in the buds and −2°C and 4°C in the shoots of ‘Campbell Early’ and ‘Muscat Baily A’ grapevines. The bHLH genes showed differential expression patterns in response to low temperatures. In ‘Campbell Early’, the expression of VlCEbHLH1, VlCEbHLH2, and VlCEbHLH5 was up-regulated, while VlCEbHLH3 was down-regulated in response to −20°C cold stress. In ‘Muscat Bailey A’, the expression of all genes was rapidly up-regulated, peaking at 6 h, then decreasing at 12 h after treatment.

The purpose of this study was to investigate responses of pear cultivars ‘Niitaka’ and ‘Chuwhangbae’ under short period heating on cold resistance level of flower buds. Experiment was conducted using annual shoots flower bud which were artificially heated (AH) during 72 hour at room condition (18–20°C). To assay for cold resistance, the cultivars were treated and observed under negative temperatures −10, −15, −20 and −25°C during the winter period in 2012 and 2013. Our findings revealed that ‘Chuwhangbae’ which was treated under control and artificial heating treatments was more resistant to low temperature than ‘Niitaka’ showing decreasing level of flower buds damages by mid-January although in early March an increasing level of damages was observed again. Cold resistant cultivar ‘Chuwhangbae’ responded more sensitively to external environments. This means that ‘Chuwhangbae’ restructures the plant protoplasts and process the transition to the new metabolic energy level in an efficient manner when triggered by effective negative temperatures thereby resulting in hardening process. We assume that this might be closely related with dormancy period, concentration of the mineral elements, water potential and transition processes of metabolism to the new energetic level. With a rise in temperature, cold tolerance in pear cultivars significantly decreased and this is related to intensive development of the floral organs. The chilling requirements for blossoming of ‘Niitaka’ was higher than ‘Chuwhangbae’.

Winter apple buds germplasm was cryopreserved in the Korean Genebank to back up the genetic resources maintained by field collections. We examined the standard two-step freezing protocol for the cryopreservation of winter buds of apple germplasm developed by National Center for Genetic Resources Preservation (NCGRP) in the USA. This protocol requires desiccation of the stem explants containing a single dormant bud to 30% moisture content, cooling at a rate of 1°C/h to −30°C for 24 hours, followed by rapid immersion in liquid nitrogen. To evaluate the viability of cryopreserved buds after at least 24 hours, the thawed and rehydrated segments are transferred to a greenhouse and used for vegetative propagation by chip budding onto rootstock or by in vitro sprouting. To optimize the protocol for the cryopreservation of winter-dormant apple buds suitable for Korean climate, we tested several treatments, including different degrees of desiccation, pre-freezing temperatures, and pre-freezing rates. The highest regeneration rates were obtained from cryopreserved samples with 35% moisture content, −35°C pre-freezing temperature, and 1°C/h pre-freezing rate. Finally, using our two-step freezing method, 14 accessions of apple germplasm were cryopreserved successfully, with an average regeneration rate of 55.0%.

Citations

Citations to this article as recorded by  

• Dormant bud cryopreservation of Rubus idaeus L.
  Olena Bobrova, Jiri Zamecnik, Milos Faltus, Alois Bilavcik
  Cryobiology.2025; 119: 105240.     CrossRef
• MATHEMATICAL MODEL FOR DESCRIBING THE POST-CRYOPRESERVATION VIABILITY OF FRUIT AND BERRY CUTTINGS
  L. V. Gorbunov
  Biotechnologia acta.2019; 12(5): 89.     CrossRef