Cryotherapy of shoot tips: a technique for pathogen eradication to produce healthy planting materials and prepare healthy plant genetic resources for cryopreservation

• Published in: Annals of applied biology Vol. 154; no. 3; pp. 351 - 363
• Main Authors: Wang, Q.C, Panis, B, Engelmann, F, Lambardi, M, Valkonen, J.P.T
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.06.2009; Blackwell Publishing Ltd; Blackwell
• Subjects: Bacteria; Bacterial plant pathogens; Banana streak virus; Biological and medical sciences; Biotechnology; Citrus; cryosurgery; cryotherapy; Cucumber mosaic virus; Fundamental and applied biological sciences. Psychology; Grapevine virus A; Ipomoea batatas; Musa; pathogen eradication; Phytopathology. Animal pests. Plant and forest protection; Phytoplasma; Plum pox virus; Potato virus Y; Prunus; Raspberry bushy dwarf virus; Rubus idaeus; Solanum tuberosum; sweet potato chlorotic stunt virus; Sweet potato feathery mottle virus; tissue culture; virus; viruses; Vitaceae; Vitis vinifera; Plant production; Biotechnology; Plant pathogen; Genetic resource; Tissue culture; Eradication; Mollicutes; Virus; pathogen eradication; Applied biology; Cryopreservation; Pathogenic; Vegetative apparatus; Prokaryote; Bacteria; Microorganism; Technique; Apex; Cryotherapy; Shoot; Phytoplasma; Planting
• ISSN: 0003-4746; 1744-7348
• DOI: 10.1111/j.1744-7348.2008.00308.x

Cryotherapy of shoot tips is a new method for pathogen eradication based on cryopreservation techniques. Cryopreservation refers to the storage of biological samples at ultra-low temperature, usually that of liquid nitrogen (-196°C), and is considered as an ideal means for long-term storage of plant germplasm. In cryotherapy, plant pathogens such as viruses, phytoplasmas and bacteria are eradicated from shoot tips by exposing them briefly to liquid nitrogen. Uneven distribution of viruses and obligate vasculature-limited microbes in shoot tips allows elimination of the infected cells by injuring them with the cryo-treatment and regeneration of healthy shoots from the surviving pathogen-free meristematic cells. Thermotherapy followed by cryotherapy of shoot tips can be used to enhance virus eradication. Cryotherapy of shoot tips is easy to implement. It allows treatment of large numbers of samples and results in a high frequency of pathogen-free regenerants. Difficulties related to excision and regeneration of small meristems are largely circumvented. To date, severe pathogens in banana (Musa spp.), Citrus spp., grapevine (Vitis vinifera), Prunus spp., raspberry (Rubus idaeus), potato (Solanum tuberosum) and sweet potato (Ipomoea batatas) have been eradicated using cryotherapy. These pathogens include nine viruses (banana streak virus, cucumber mosaic virus, grapevine virus A, plum pox virus, potato leaf roll virus, potato virus Y, raspberry bushy dwarf virus, sweet potato feathery mottle virus and sweet potato chlorotic stunt virus), sweet potato little leaf phytoplasma and Huanglongbing bacterium causing 'citrus greening'. Cryopreservation protocols have been developed for a wide variety of plant species, including agricultural and horticultural crops and ornamental plants, and can be used as such or adjusted for the purpose of cryotherapy.