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Cryopreservation of apple (Malus domestica 'Benoni') dormant buds using two-step freezing method

Gupta, S., Mir, J. I.
Acta horticulturae 2019 no.1234 pp. 323-328
Malus domestica, apples, branches, buds, cryopreservation, cultivars, freezers, freezing, fruit trees, fruits, gene banks, germplasm, horticulture, liquids, nitrogen, plant genetic resources, silica gel, storage temperature, India
Apple is the most important temperate fruit in India. The top apple producing states are Jammu and Kashmir (J&K), Himachal Pradesh (HP) and Uttarakhand (UK). The apple germplasm is mainly conserved in the field genebanks at the ICAR-National Bureau of Plant Genetic Resource’s Regional Station, Shimla (HP) and Bhowali (UK); ICAR-Central Institute of Temperate Horticulture, Srinagar (J&K); ICAR-Indian Agricultural Research Institute’s Regional Station, Shimla (HP); Dr. Y.S. Parmar University of Horticulture and Forestry, Solan (HP); Govind Ballabh Pant University of Agriculture and Technology, Pantnagar (UK); Sher-e-Kashmir University of Agricultural Science and Technology, Srinagar (J&K). To have a backup, some accessions are being maintained under in vitro genebank at New Delhi. For long-term conservation of apple accessions, cryopreservation is the only method. Dormant buds of apple (Malus domestica ‘Benoni’) were cryopreserved by two-step freezing method. Apple twigs were collected from Srinagar at the sub-freezing temperature. Twigs were stored at 5-6°C until use. The buds were scooped from the twigs and desiccated on silica gel. Then the buds were subjected to gradual low temperature treatments up to -30°C before submerging into liquid nitrogen. Programmable freezer was not used for freezing treatments. Post-thaw recovery (in vitro) was about 20%. The average rate of shoot formation was about 80%. This protocol of two-step freezing method was successfully applied to other three apple cultivars with the post-thaw in vitro recovery about 11-40%. This method appears to be a promising technique for cryopreserving dormant buds from field grown apple trees.