Survival and ultrastructural features of peach palm (Bactris gasipaes, Kunth) somatic embryos submitted to cryopreservation through vitrification

Cryopreservation of Duckweed Genetic Diversity as Model for Long-Term Preservation of Aquatic Flowering Plants

Vegetatively propagating aquatic angiosperms, the Lemnaceae family (duckweeds) represents valuable genetic resources for circular bioeconomics and other sustainable applications. Due to extremely fast growth and laborious cultivation of in vitro collections, duckweeds are an urgent subject for cryopreservation. We developed a robust and fast DMSO-free protocol for duckweed cryopreservation by vitrification. A single-use device was designed for sampling of duckweed fronds from donor culture, further spin-drying, and subsequent transferring to cryo-tubes with plant vitrification solution 3 (PVS3). Following cultivation in darkness and applying elevated temperatures during early regrowth stage, a specific pulsed illumination instead of a diurnal regime enabled successful regrowth after the cryopreservation of 21 accessions of Spirodela, Landoltia, Lemna, and Wolffia genera, including interspecific hybrids, auto- and allopolyploids. Genome size measurements revealed no quantitative genomic changes potentially caused by cryopreservation. The expression of CBF/DREB1 genes, considered as key factors in the development of freezing tolerance, was studied prior to cooling but was not linked with duckweed regrowth after rewarming. Despite preserving chlorophyll fluorescence after rewarming, the rewarmed fronds demonstrated nearly zero photosynthetic activity, which did not recover. The novel protocol provides the basis for future routine application of cryostorage to duckweed germplasm collections, saving labor for in vitro cultivation and maintaining characterized reference and mutant samples.

Mitigation of the effects of salt stress in cowpea bean through the exogenous aplication of brassinosteroid

Cowpea (Vigna unguiculata (L.) Walp.) is a legume widely cultivated by small, medium and large producers in several Brazilian regions. However, one of the concerns for the production of cowpea in Brazil in recent years is the low rainfall activity in these regions, which generates the accumulation of salts on the surface. The objective of this work was to evaluate the effects of salt stress on growth parameters and enzyme activity in cowpea plants at different concentrations of brassinosteroids. Experiment was developed in a greenhouse using a completely randomized experimental design in a 3 x 3 factorial scheme. The treatments consisted of three levels of brassinosteroids (0, 3 and 6 µM EBL) and three levels of salt stress (0, 50 and 100 mM NaCl). Growth factors (height, diameter and number of leaves) decreased in the saline condition. With the presence of brassinosteroid the height did not increase, but the number of leaves did, mainly in the saline dosage of 100 mM NaCl. In the variable membrane integrity, brassinosteroid was efficient in both salinity dosages, the same not happening with the relative water content, where the saline condition did not affect the amount of water in the vegetable, with the application of brassino it remained high, decreasing only at dosage 100 mM NaCl. The nitrate reductase enzyme was greatly affected in the root system even with the application of increasing doses of brassino. Therefore, brassinosteroids as a promoter of saline tolerance in cowpea seedlings was positive. The concentration of 3µM of EBL provided the most satisfactory effect in tolerating the deleterious effects of the saline condition. The same cannot be concluded for the concentration of 6µM of EBL that did not promote tolerance to some variables.

Review: The case for studying mitochondrial function during plant cryopreservation

Cryopreservation has several advantages over other ex situ conservation methods, and indeed is the only viable storage method for the long term conservation of most plant species. However, despite many advances in this field, it is increasingly clear that some species are ill-equipped to overcome the intense stress imposed by the cryopreservation process, making protocol development incredibly difficult using traditional trial and error methods. Cryobiotechnology approaches have been recently recognised as a strategic way forward, utilising intimate understanding of biological systems to inform development of more effective cryopreservation protocols. Mitochondrial function is a model candidate for a cryobiotechnological approach, as it underpins not only energy provision, but also several other key determinants of germplasm outcome, including stress response, reduction-oxidation status, and programmed cell death. Extensive research in animal cell and tissue cryopreservation has established a clear link between mitochondrial health and cryopreservation survival, but also indicates that mitochondria are routinely subject to damage from multiple aspects of the cryopreservation process. Evidence is already emerging that mitochondrial dysfunction may also occur in plant cryopreservation, and this research can be greatly expanded by using considered applications of innovative technologies. A range of mitochondria-targeted prophylactic and therapeutic interventions already exist with potential to improve cryopreservation outcomes through mitochondrial function.

Cryopreservation of oil palm (Elaeis guineensis Jacq.)

Oil palm (Elaeis guineensis Jacq.), a tropical plant, is the leading source of edible oil. This review deals with the cryopreservation of oil palm as a way to preserve this important tropical germplasm. Somatic embryos have been the most popular source of material for cryopreservation as they are propagules that are effectively produced during micropropagation. In contrast, fewer studies exist on the cryopreservation of pollen, zygotic embryos, seeds, kernels and embryogenic cell suspensions. This review highlights the ideal protocols, in detail, in a bid to offer guidance for further advances in oil palm cryopreservation.