Cryopreservation of virus: A novel biotechnology for long-term preservation of virus in shoot tips

Abstract

Background: Preservation of plant virus is a fundamental requirement in all types of virus-related research and applied applications. Development of efficient, reliable strategies for long-term preservation of plant virus would largely assist these studies. Results: The present study reported a novel biotechnology allowing cryopreservation of Apple stem grooving virus (ASGV) in living shoot tips. Following cryopreservation by droplet-vitrification or encapsulation-dehydration, about 62-67% of shoot regrowth and 100% of ASGV cryopreservation were obtained. Although shoot proliferation and virus concentration were reduced in cryopreserved diseased shoots after 8weeks of shoot regeneration, continuous subculture for 4 times (16weeks) increased shoot proliferation and virus concentration to comparative levels as those produced by shoot tip culture (as a control to shoot tip cryopreservation). Cryopreserved ASGV was efficiently transmitted to a woody plant by micrografting and to a herbaceous indicator by mechanical inoculation. Gene sequencing in three fragments of ASGV genome including coat protein and movement protein showed that cryopreserved ASGV shared 99.87% nucleotide identities with shoot tip culture-preserved virus, indicating cryopreserved virus is genetically stable. Conclusions: The present study demonstrates ASGV, a representative virus that can infect meristematic cells of shoot tips, can be efficiently cryopreserved in shoot tips. To the best of our knowledge, this is the first report on plant virus cryopreservation in living tissues, and has great potential applications to long-term preservation of plant viruses.