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

Abstract

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.

Asymbiotic in vitro seed propagation of Dendrobium

“…Another strategy is to use seeds aseptically germinated in vitro, under optimized conditions, modeling natural ones. The ease and high germination percentage of seeds of Dendrobium species (Table 1) under asymbiotic conditions relative to the more precise requirements of symbiotic germination, which needs to balance germination and pathogenesis (Teixeira da Silva et al 2015b), makes this technique more practical and useful for mass in vitro propagation and/or germplasm conservation (Teixeira da Silva et al 2014b).…”

Tissue disinfection for preparation of Dendrobium in vitro culture

“…Use of in vitro symbiotic germination is another way to improve Dendrobium micropropagation (Teixeira da Silva et al 2015c) but the introduction of symbionts poses a significant challenge to the in vitro culture of orchids because the balance between the need for the symbiont and the need to maintain a sterile culture, i.e., without the symbiont growing excessively and killing the plant tissues as a result of exposure to a nutrient-rich environment, is a tremendous challenge in orchid biotechnology. For example, observed improved (almost 100%) seed germination by co-cultivation of a fungus Sebacina sp.…”

“…Using these principles, this review seeks to find how disinfection procedures have been used to prepare in vivo-derived plant material for in vitro culture in Dendrobium since the in vitro environment serves as an important tool for multiple biotechnological advances, symbiotic and asymbiotic seed germination, and molecular advances, including genetic transformation (Teixeira da Silva et al 2015aSilva et al , 2015bSilva et al , 2015c.…”

Selection of relatively exact reference genes for gene expression studies in goosegrass (Eleusine indica) under herbicide stress

“…In general, resistance mechanisms can be categorized as target and non-target14. Gene expression analysis is commonly applied to explore target-site gene amplification and the over-expression of detoxifying enzyme genes, which are related to herbicide resistance151617. Quantitative real-time PCR (qPCR) is necessarily in wide use18.…”