Telomere Length in Norway Spruce during Somatic Embryogenesis and Cryopreservation

Current status of the cryopreservation of embryogenic material of woody species

Cryopreservation, or the storage at liquid nitrogen temperatures (-196°C), of embryogenic cells or somatic embryos allows their long-term conservation without loss of their embryogenic capacity. During the last decade, protocols for cryopreservation of embryogenic material of woody species have been increasing in number and importance. However, despite the large experimental evidence proved in thousands of embryogenic lines, the application for the large-scale conservation of embryogenic material in cryobanks is still limited. Cryopreservation facilitates the management of embryogenic lines, reducing costs and time spent on their maintenance, thus limiting the risk of the appearance of somaclonal variation or contamination. Somatic embryogenesis in combination with cryopreservation is especially useful to preserve the juvenility of lines while the corresponding clones are being field-tested. Hence, when tree performance has been evaluated, selected varieties can be propagated from the cryostock. The traditional method of slow cooling or techniques based on vitrification are mostly applied procedures. For example, slow cooling methods are widely applied to conserve embryogenic lines of conifers. Desiccation based procedures, although simpler, have been applied in a smaller number of species. Genetic stability of the cryopreserved material is supported by multiloci PCR-derived markers in most of the assayed species, whereas DNA methylation status assays showed that cryopreservation might induce some changes that were also observed after prolonged subculture of the embryogenic lines. This article reviews the cryopreservation of embryogenic cultures in conifers, fruit species, deciduous forest species and palms, including a description of the different cryopreservation procedures and the analysis of their genetic stability after storage in liquid nitrogen.

Conifer Biotechnology: An Overview

The peculiar characteristics of conifers determine the difficulty of their study and their great importance from various points of view. However, their study faces numerous important scientific, methodological, cultural, economic, social, and legal challenges. This paper presents an approach to several of those challenges and proposes a multidisciplinary scientific perspective that leads to a holistic understanding of conifers from the perspective of the latest technical, computer, and scientific advances. This review highlights the deep connection that all scientific contributions to conifers can have in each other as fully interrelated communicating vessels.

Cryopreservation of Fraxinus mandshurica Rupr. by Using the Slow Cooling Method

Cryopreservation is an important method for the excellent long-term preservation of plant germplasm. This study explores an optimal cryopreservation technology for the embryogenic callus of Fraxinus mandshurica to effectively maintain its genetic stability and morphogenesis potential. The optimal cryopreservation conditions were assessed using the embryogenic callus of F. mandshurica as the material, and the slow cooling method was optimized for its cryopreservation. The results indicated that the preculture of embryogenic callus in 0.4 mol·L−1 sorbitol solution for 20 h at room temperature, followed by its cryoprotection in 7.5% dimethyl sulfoxide solution at 0 °C for 90 min, constituted the optimal material treatment method. The freezing tube was placed in a −80 °C refrigerator for 2 h and then quickly put into liquid nitrogen for frozen storage. During thawing, the cryopreservation tube was taken out from liquid nitrogen, directly placed in a water bath at 40 °C for 2 min, and used for culturing on the woody plant media + 0.1 mg·L−1 6-benzyladenine + 0.15 mg·L−1 2, 4-dichlorophenoxyacetic acid. After cryopreservation using the slow cooling method, the highest survival rate of callus cells was 80.82%. The fresh weight reached 1.93 g after 60-day recovery culture. The regeneration rate and the proliferation coefficient of the callus were 100% and 2.79, respectively. The differentiation rate was 56.83%, and the emergence rate was 23.59%. The results provide a scientific basis for the long-term preservation of F. mandshurica germplasm resources.

Somatic Embryogenesis of Norway Spruce and Scots Pine: Possibility of Application in Modern Forestry

Somatic embryogenesis (SE) is an important method for the vegetative propagation of trees. SE is the developmental in vitro process in which embryos are produced from somatic cells. This method can be integrated with other biotechnological techniques, genomic breeding and cryopreservation, which enables commercial-scale sapling production of selected high-yielding genotypes in wood production combined with fast breeding cycles. The SE is potential tool to improve plant stock in comparison with seed orchards. It can be useful for ecologically and economically important species, such as Norway spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.), ensuring stable production in the era of climate change and biodiversity crisis. In this review, we summarize the current state of research on problems associated with somatic embryogenesis in P. abies and P. sylvestris.