Root cryobanking: an important tool in plant cryopreservation

Abstract

Cryopreservation in liquid nitrogen (− 196 °C) ensures safe and cost-effective conservation of plant genetic resources using diverse materials, including roots. To date, successful cryopreservation of root explants isolated from in vitro grown plants as well as adventitious and hairy root cultures has been reported in large numbers of plant species. In particular, significant progress has been made in cryopreserving in vitro cultures of adventitious and hairy roots that attract both scientific and commercial interest as an alternative source of plant-derived bioactive compounds with potential application in pharmaceutical, cosmetic, and natural health product industries. The process of cryopreservation has been shown to have little or no impact on growth, and biosynthetic and genetic stability of roots following recovery in an ambient growth environment. However, structural integrity of roots is critical for successful cryopreservation as thin and fragile root tips are very sensitive to stressful conditions associated with various steps of a cryopreservation protocol and a thorough optimization of each step, particularly the treatment with vitrification solution, is essential. This review summarizes the results of recent studies on cryopreservation of plant roots and highlights the importance of continued research in this area. Roots are uniquely suited for long term conservation of plant genetic resources due to their ease of excision, in vitro maintenance, and the ability to undergo morphogenesis. The root based regeneration and cryopreservation systems offer excellent opportunities to investigate a range of regulatory signalling and adaptation mechanisms that are activated in response to physical and chemical stresses. This review summarizes the results of recent studies on cryopreservation of plant roots, including hairy and adventitious root cultures used in biotechnology, and underpins their significance in biobanking of economically important food, ornamental, and medicinal crops, as well as, endangered plant species.