Cryopreservation of Pinus radiata zygotic embryo cotyledons: effect of storage duration on adventitious shoot formation and plant growth after 2 years in the field

Abstract

This work is the first report of the cryopreservation of conifer cotyledons without cryoprotectants and their subsequent shoot regeneration and successful establishment of a field trial. Multiple genotypes of radiata pine (Pinus radiata D. Don) embryo cotyledons were stored in liquid nitrogen following a desiccation treatment. Cotyledons that had been stored in liquid nitrogen for 7, 14, and 28 days were compared with noncryopreserved cotyledons for adventitious shoot production, root formation on the shoots, and plant growth after 2 years in the field. Of the 72 genotypes tested, 79%–87% of them produced shoots on at least one treatment and 59% of them produced shoots on all treatments. Rooting rates of shoots were not affected by treatment, with the cryopreserved treatments rooting as well as the noncryopreserved controls. Height growth of plants in the nursery was similar across all treatments after 2 years but was influenced by setting date. The higher genotype capture possible with adventitious methodologies, compared with that of somatic embryogenesis, and the preservation of juvenile characteristics while material is stored in liquid nitrogen make adventitious methods worthy of intensive study for possible commercial application.