Cryoconservation de matériel génétique de bananier

Les bananiers et les bananiers plantains (les différentes espèces de Musa) produisent des aliments de base importants dans les régions tropicales et subtropicales. La conservation des ressources génétiques de ces espèces en toute sûreté est capitale, dans la mesure où la disponibilité de ce matériel génétique permettra de nouveaux efforts d’amélioration et d’adaptation à de nouvelles conditions environnementales. Cette publication fournit des informations sur les méthodologies de cryoconservation adaptées aux espèces du genre Musa

Cryopreservation of Musa germplasm

Bananas and plantains (Musa species) are important food staples in the tropics and subtropics. This germplasm needs to be safely conserved to ensure that it is available for future breeding efforts for improved production and adaptation to changing environmental conditions. This booklet provides information on cryopreservation methodologies suitable for Musa species

Genetic diversity and core subset selection in ex situ seed collections of the banana crop wild relative Musa balbisiana

Crop wild relatives (CWRs) play a key role in crop breeding by providing beneficial trait characteristics for improvement of related crops. CWRs are more efficiently used in breeding if the plant material is genetically characterized, but the diversity in CWR genetic resources has often poorly been assessed. Seven seed collections of Musa balbisiana, an important CWR of dessert and cooking bananas, originating from three natural populations, two feral populations and two ex situ field collections were retrieved and their genetic diversity was quantified using 18 microsatellite markers to select core subsets that conserve the maximum genetic diversity. The highest genetic diversity was observed in the seed collections from natural populations of Yunnan, a region that is part of M. balbisiana's centre of origin. The seeds from the ex situ field collections were less genetically diverse, but contained unique variation with regards to the diversity in all seed collections. Seeds from feral populations displayed low genetic diversity. Core subsets that maximized genetic distance incorporated almost no seeds from the ex situ field collections. In contrast, core subsets that maximized allelic richness contained seeds from the ex situ field collections. We recommend the conservation and additional collection of seeds from natural populations, preferentially originating from the species' region of origin, and from multiple individuals in one population. We also suggest that the number of seeds used for ex situ seed bank regeneration must be much higher for the seed collections from natural populations

Cryopreservation of Abies alba embryogenic tissues by slow-freezing method

Embryogenic tissues of Abies alba Mill. were cryopreserved using the slow-freezing approach. Four cell lines were incubated for 24 h on a medium with 0.5 M sorbitol and pre-treated with 5% DMSO. Subsequently, the tissues were frozen at a cooling rate of 1 °C min-1 to -40 °C and transferred to liquid nitrogen for 72 hours. After thawing in a water bath at 40 °C, the tissues were cultivated on a proliferation medium. All tested lines recovered, but variations in regrowth frequencies across cell lines were noticed (91.66 to 100%). The recovered tissues showed similar features to the control 2 (non-pre-treated and non-cryopreserved tissues). In the accumulation of fresh and dry mass, no statistically significant differences were observed between cryopreserved cultures and control 2. The cryopreserved tissues produced cotyledonary somatic embryos capable of germination. Microscopic observations revealed considerable structural changes as a consequence of the cryopreservation procedure. The long vacuolated suspensor cells were disrupted, and mostly the meristematic cells of the embryonal region survived. The typical bipolar structure of early somatic embryos has been regained during the post-thaw period. Differences in cryotolerance across cell lines were also observed

Challenges and prospects for the conservation of crop genetic resources in field genebanks, in In Vitro collections and/or in liquid nitrogen.

The conservation of crop genetic resources, including their wild relatives, is of utmost importance for the future of mankind. Most crops produce orthodox seeds and can, therefore, be stored in seed genebanks. However, this is not an option for crops and species that produce recalcitrant (non-storable) seeds such as cacao, coffee and avocado, for crops that do not produce seeds at all; therefore, they are inevitably vegetatively propagated such as bananas, or crops that are predominantly clonally propagated as their seeds are not true to type, such as potato, cassava and many fruit trees. Field, in vitro and cryopreserved collections provide an alternative in such cases. In this paper, an overview is given on how to manage and setup a field, in vitro and cryopreserved collections, as well as advantages and associated problems taking into account the practical, financial and safety issues in the long-term. In addition, the need for identification of unique accessions and elimination of duplicates is discussed. The different conservation methods are illustrated with practical examples and experiences from national and international genebanks. Finally, the importance of establishing safe and long-term conservation methods and associated backup possibilities is highlighted in the frame of the global COVID-19 pandemic

Cryopreservation of Abies alba embryogenic tissues by slow-freezing method

Embryogenic tissues of Abies alba Mill. were cryopreserved using the slow-freezing approach. Four cell lines were incubated for 24 h on a medium with 0.5 M sorbitol and pre-treated with 5% DMSO. Subsequently, the tissues were frozen at a cooling rate of 1 °C min-1 to -40 °C and transferred to liquid nitrogen for 72 hours. After thawing in a water bath at 40 °C, the tissues were cultivated on a proliferation medium. All tested lines recovered, but variations in regrowth frequencies across cell lines were noticed (91.66 to 100%). The recovered tissues showed similar features to the control 2 (non-pre-treated and non-cryopreserved tissues). In the accumulation of fresh and dry mass, no statistically significant differences were observed between cryopreserved cultures and control 2. The cryopreserved tissues produced cotyledonary somatic embryos capable of germination. Microscopic observations revealed considerable structural changes as a consequence of the cryopreservation procedure. The long vacuolated suspensor cells were disrupted, and mostly the meristematic cells of the embryonal region survived. The typical bipolar structure of early somatic embryos has been regained during the post-thaw period. Differences in cryotolerance across cell lines were also observed

Physiological and structural aspects of in vitro somatic embryogenesis in Abies alba Mill

Initiation of somatic embryogenesis fromimmature zygotic embryos, long-term maintenance of embryogenic tissue in vitro or by cryopreservation, as well as maturation, of somatic embryos of Abies alba Mill. are reported in this study. For the initiation of embryogenic tissues, a DCR medium containing di erent types of cytokinins (1 mg.L1) were tested. During three consecutive years, 61 cell lines were initiated out of 1308 explants, with initiation frequencies ranging between 0.83 and 13.33%. The type of cytokinin had no profound e ect on the initiation frequency within one given year. Microscopic observations revealed presence of bipolar somatic embryos in all initiated embryogenic tissues. Besides the typical bipolar somatic embryos, huge polyembryonal complexes, as well as “twin” embryos, were observed. Maturation of somatic embryos occurred on a DCR medium supplemented by abscisic acid (10 mg.L1), polyethylene glycol (PEG-4000, 7.5%) and 3% maltose. The maturation capacity was cell-line dependent. All of the four tested cell lines produced cotyledonary somatic embryos, though at di erent quantities, of 16 to 252 per g of fresh weight. After germination, seedlings developed, but their further growth soon stopped after the formation of a resting bud. Altogether, seven cell lines were cryopreserved, using the slow-freezing technique. After rewarming, all tested cell lines showed regrowth rates between 81.8 and 100%

Development of the first axillary in vitro shoot multiplication protocol for coconut palms

The coconut palm or “tree of life” is one of nature’s most useful plants and the demand for its fruit is increasing. However, coconut production is threatened by ageing plantations, pests and diseases. Currently, the palm is exclusively propagated via seeds, limiting the amount of planting material. A novel micropropagation method is presented, based on axillary shoot formation. Apical meristems of in vitro coconut seedlings are cultured onto Y3 medium containing 1 µM TDZ. This induces the apical meristem to proliferate through axillary shoots in ~ 27% of the initiated explants. These axillary shoots are seen as white clumps of proliferating tissue and can be multiplied at a large scale or regenerated into rooted in vitro plantlets. This innovative micropropagation method will enable the production of disease-free, high quality in vitro plantlets, which will solve the worldwide scarcity of coconut planting material

Cryopreservation and In Vitro banking: a cool subject – Preface from the editors

Plant breeding depends largely on having access to a wide variety of plant genetic resources, which are vulnerable to losses caused by biotic and abiotic threats when grown in the field or in a greenhouse. Thus, cryopreservation or in vitro banking is a safe strategy for long-term conservation of such genetic resources, which serves as back-up collections for field genebanks and reduces. For many species, encapsulation technologies can be a promising tool for the management of plant material of high quality, the production in nurseries of plants from in vitro culture, or the conservation of plant genetic resources. Such “synthetic seeds” proved to be of great value in the medium- (slow-growth storage) and long-term (cryopreservation) conservation of germplasm of fruit, ornamental, horticultural and forestry species in small spaces. However, more research is still needed. Cryopreservation projects must have clear goals, long-term funding, skilled technical support staff, necessary infrastructure, and well-defined procedures and protocols, so that they can be routinely implemented in plant cryobanks and help to establish backup collections of valuable plant genetic resources