Mulberry biodiversity conservation through cryopreservation

Abstract

A 238 mulberry germplasm accession collection from diverse regions maintained under tropical conditions was identified from an ex situ field gene bank. The purpose was to prioritize the in vitro conservation and cryopreservation to develop long-term biodiversity conservation for ensuring sustainable utilization of these valuable resources. Reliable cryo techniques using desiccation and slow freezing of winter-dormant buds were used. Storage potential of bud grafts of different Morus species at −1.5°C for 90 d indicated species-specific variation, and most of the wild species were found sensitive. In vitro regeneration and cryopreservation (−196°C) protocols using differentiated bud meristems, like axillary winter-dormant buds, were worked out for a wide range of landraces, wild, and cultivated varieties of Morus. Buds maintained under subtropical location are also amenable for cryopreservation. Successful cryopreservation of winter-dormant buds belonging to Morus indica, Morus alba, Morus latifolia, Morus cathayana, Morus laevigata, Morus nigra, Morus australis, Morus bombycis, Morus sinensis, Morus multicaulis, and Morus rotundiloba was achieved. Among wild species, Morus tiliaefolia and Morus serrata showed moderate recovery after cryopreservation. Survival rates did not alter after 3 yr of cryopreservation. Inter-simple sequence repeat markers were used to ascertain the genetic stability of cryopreserved mulberry germplasm accessions, which showed no difference detected among the plantlets regenerated from frozen apices in comparison to the nonfrozen material.