Asymbiotic in vitro seed propagation of Dendrobium

The ability to germinate orchids from seeds in vitro presents a useful and viable method for the propagation of valuable germplasm, maintaining the genetic heterogeneity inherent in seeds. Given the ornamental and medicinal importance of many species within the genus Dendrobium, this review explores in vitro techniques for their asymbiotic seed germination. The influence of abiotic factors (such as temperature and light), methods of sterilization, composition of basal media, and supplementation with organic additives and plant growth regulators are discussed in context to achieve successful seed germination, protocorm formation, and further seedling growth and development. This review provides both a basis for the selection of optimal conditions, and a platform for the discovery of better ones, that would allow the development of new protocols and the exploration of new hypotheses for germination and conservation of Dendrobium seeds and seedlings.

Symbiotic in vitro seed propagation of Dendrobium: fungal and bacterial partners and their influence on plant growth and development

The genus Dendrobium is one of the largest genera of the Orchidaceae Juss. family, although some of its members are the most threatened today. The reason why many species face a vulnerable or endangered status is primarily because of anthropogenic interference in natural habitats and commercial overexploitation. The development and application of modern techniques and strategies directed towards in vitro propagation of orchids not only increases their number but also provides a viable means to conserve plants in an artificial environment, both in vitro and ex vitro, thus providing material for reintroduction. Dendrobium seed germination and propagation are challenging processes in vivo and in vitro, especially when the extreme specialization of these plants is considered: (1) their biotic relationships with pollinators and mycorrhizae; (2) adaptation to epiphytic or lithophytic life-styles; (3) fine-scale requirements for an optimal combination of nutrients, light, temperature, and pH. This review also aims to summarize the available data on symbiotic in vitro Dendrobium seed germination. The influence of abiotic factors as well as composition and amounts of different exogenous nutrient substances is examined. With a view to better understanding how to optimize and control in vitro symbiotic associations, a part of the review describes the strong biotic relations of Dendrobium with different associative microorganisms that form microbial communities with adult plants, and also influence symbiotic seed germination. The beneficial role of plant growth-promoting bacteria is also discussed.