An amalgam of pathogenic and beneficial endophytic fungi colonizing four Dendrobium species from Meghalaya, India

Extract from endophytic Fusarium isolates stimulates seed germination of the host and protocorm development of non-host orchids

We isolated endophytic Fusarium strains from the healthy roots, stems, and leaves of Dendrobium moschatum to investigate their plant growth-promoting activities in vitro. Subsequently, Indole acetic acid (IAA) was quantified and the IaaM gene (responsible for IAA synthesis in fungi) was amplified and sequenced. Finally, a germination assay was performed with seeds of D. moschatum and a plant growth assay with protocorms of Dendrobium longicornu to test their plant growth-promoting activities. Five Fusarium isolates (CDS11, PDL1, PDL3, PDR6, PDR7) were identified in this study. The highest amount (60µgml-1) of indole acetic acid was recorded in the PDR7 extract, whereas it was not detected in PDR6 and CDS11. The fungal extracts of isolates PDR6 and PDR7 were highly effective for seed germination by approximately 80% and 90% (respectively) of the host plant. The fungal extract of PDR7 showed a high IAA content and promoted in vitro seed germination of the host (D. moschatum) and protocorm development of the non-host (D. longicornu). In contrast, IAA content in the fungal extract of PDR6 remained undetected but was effective in both seed germination and protocorm development. Our results demonstrated the potential beneficial application of endophytic Fusarium in orchid mass propagation.

Enhancing dendrobine production in Dendrobium nobile through mono-culturing of endophytic fungi, Trichoderma longibrachiatum (MD33) in a temporary immersion bioreactor system

INTRODUCTION

Dendrobine, a valuable alkaloid found in Dendrobium nobile, possesses significant pharmaceutical potential.

METHODS

In this study, we explored innovative approaches to enhance dendrobine production by utilizing endophytic fungi in a Temporary Immersion Bioreactor System (TIBS, Nanjing BioFunction Co. Ltd., China) and traditional test bottles. Dendrobine was unequivocally identified and characterised in D. nobile co-culture seedlings through UHPLC analysis and LC-MS qTOF analysis, supported by reference standards.

RESULTS

The CGTB (control group) and EGTB (experimental group) 12-month-old D. nobile seedlings exhibited similar peak retention times at 7.6±0.1 minutes, with dendrobine identified as C16H25NO2 (molecular weight 264.195). The EGTB, co-cultured with Trichoderma longibrachiatum (MD33), displayed a 2.6-fold dendrobine increase (1804.23 ng/ml) compared to the CGTB (685.95 ng/ml). Furthermore, a bioanalytical approach was applied to investigate the mono-culture of T. longibrachiatum MD33 with or without D. nobile seedlings in test bottles. The newly developed UHPLC-MS method allowed for dendrobine identification at a retention time of 7.6±0.1 minutes for control and 7.6±0.1 minutes for co-culture. Additionally, we explored TIBS to enhance dendrobine production. Co-culturing D. nobile seedlings with Trichoderma longibrachiatum (MD33) in the TIBS system led to a substantial 9.7-fold dendrobine increase (4415.77 ng/ml) compared to the control (454.01 ng/ml) after just 7 days. The comparative analysis of dendrobine concentration between EGTB and EGTIBS highlighted the remarkable potential of TIBS for optimizing dendrobine production. Future research may focus on scaling up the TIBS approach for commercial dendrobine production and investigating the underlying mechanisms for enhanced dendrobine biosynthesis in D. nobile. The structural elucidation of dendrobine was achieved through 1H and 13C NMR spectroscopy, revealing a complex array of proton environments and distinct carbon environments, providing essential insights for the comprehensive characterization of the compound.

DISCUSSION

These findings hold promise for pharmaceutical and industrial applications of dendrobine and underline the role of endophytic fungi in enhancing secondary metabolite production in medicinal plants.

Endophytic fungal communities and their biotechnological implications for agro-environmental sustainability

Endophytic fungal communities have attracted a great attention to chemists, ecologists, and microbiologists as a treasure trove of biological resource. Endophytic fungi play incredible roles in the ecosystem including abiotic and biotic stress tolerance, eco-adaptation, enhancing growth and development, and maintaining the health of their host. In recent times, endophytic fungi have drawn a special focus owing to their indispensable diversity, unique distribution, and unparalleled metabolic pathways. The endophytic fungal communities belong to three phyla, namely Mucoromycota, Basidiomycota, and Ascomycota with seven predominant classes Agaricomycetes, Dothideomycetes, Eurotiomycetes, Mortierellomycotina, Mucoromycotina, Saccharomycetes, and Sordariomycetes. In a review of a huge number of research finding, it was found that endophytic fungal communities of genera Aspergillus, Chaetomium, Fusarium, Gaeumannomyces, Metarhizium, Microsphaeropsis, Paecilomyces, Penicillium, Piriformospora, Talaromyces, Trichoderma, Verticillium, and Xylaria have been sorted out and well characterized for diverse biotechnological applications for future development. Furthermore, these communities are remarkable source of novel bioactive compounds with amazing biological activity for use in agriculture, food, and pharmaceutical industry. Endophytes are endowed with a broad range of structurally unique bioactive natural products, including alkaloids, benzopyranones, chinones, flavonoids, phenolic acids, and quinines. Subsequently, there is still an excellent opportunity to explore novel compounds from endophytic fungi among numerous plants inhabiting different niches. Furthermore, high-throughput sequencing could be a tool to study interaction between plants and endophytic fungi which may provide further opportunities to reveal unknown functions of endophytic fungal communities. The present review deals with the biodiversity of endophytic fungal communities and their biotechnological implications for agro-environmental sustainability.

How Mycorrhizal Associations Influence Orchid Distribution and Population Dynamics

Orchid distribution and population dynamics are influenced by a variety of ecological factors and the formation of holobionts, which play key roles in colonization and ecological community construction. Seed germination, seedling establishment, reproduction, and survival of orchid species are strongly dependent on orchid mycorrhizal fungi (OMF), with mycorrhizal cheating increasingly observed in photosynthetic orchids. Therefore, changes in the composition and abundance of OMF can have profound effects on orchid distribution and fitness. Network analysis is an important tool for the study of interactions between plants, microbes, and the environment, because of the insights that it can provide into the interactions and coexistence patterns among species. Here, we provide a comprehensive overview, systematically describing the current research status of the effects of OMF on orchid distribution and dynamics, phylogenetic signals in orchid-OMF interactions, and OMF networks. We argue that orchid-OMF associations exhibit complementary and specific effects that are highly adapted to their environment. Such specificity of associations may affect the niche breadth of orchid species and act as a stabilizing force in plant-microbe coevolution. We postulate that network analysis is required to elucidate the functions of fungal partners beyond their effects on germination and growth. Such studies may lend insight into the microbial ecology of orchids and provide a scientific basis for the protection of orchids under natural conditions in an efficient and cost-effective manner.