Arbuscular mycorrhizal fungi (AMF) establishing beneficial symbiosis with most crop plants have gained a growing interest as agro-ecosystem service providers able to sustain crop productivity and quality. In this study we tested the agronomic relevance of field-inoculated locally sourced and foreign inocula on chickpea ( Cicer arietinum L.), one of the most important worldwide grain legumes. The foreign AMF Funneliformis mosseae and Rhizophagus irregularis were used as single and dual species inocula. Crop growth and productivity, plant nutrient uptakes and protein, Fe and Zn grain biofortification were assessed under a rainfed low-input cropping system after autumn and spring sowings. Uni- and multivariate analyses of data showed that AM fungal field inoculation increased chickpea AM fungal root colonization as well as plant biomass and yield. In addition, AMF were also effective in improving the nutritional value of grain by protein, Fe and Zn biofortification. The locally sourced AM fungal inoculum was more efficient then the foreign ones in Fe and Zn grain biofortification and, in the spring sowing treatment, also in improving yield and grain protein content. These findings enhance our understanding of the field potential role of AMF showing that a mycorrhiza-friendly approach in agriculture may have great potential in biofertilization of crops and biofortification of foods.

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Enhancing ecosystem services in sustainable agriculture: Biofertilization and biofortification of chickpea (Cicer arietinum L.) by arbuscular mycorrhizal fungi

Plant roots are major transmitters of atmospheric carbon into soil. The rhizosphere, the soil volume around living roots influenced by root activities, represents hotspots for organic carbon inputs, microbial activity, and carbon turnover. Rhizosphere processes remain poorly understood and the observation of key mechanisms for carbon transfer and protection in intact rhizosphere microenvironments are challenging. We deciphered the fate of photosynthesis-derived organic carbon (OC) in intact wheat rhizosphere, combining stable isotope labeling at field scale with high-resolution 3D-imaging. We used nano-scale secondary ion mass spectrometry and focus ion beam-scanning electron microscopy to generate insights into rhizosphere processes at nanometer scale. In immature wheat roots, the carbon circulated through the apoplastic pathway, via cell walls, from the stele to the cortex. The carbon was transferred to substantial microbial communuties, mainly represented by bacteria surrounding peripheral root cells. Iron oxides formed bridges between roots and bigger mineral particles, such as quartz, and surrounded bacteria in microaggregates close to the root surface. Some microaggregates were also intimately associated with the fungal hyphae surface. Based on these results, we propose a conceptual model depicting the fate of carbon at biogeochemical interfaces in the rhizosphere, at the forefront of growing roots. We observed complex interplays between vectors (roots, fungi, bacteria), transferring plant-derived OC into root-free soil and stabilizing agents (iron oxides, root and microorganism products), potentially protecting plant-derived OC within microaggregates in the rhizosphere.

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Linking 3D Soil Structure and Plant-Microbe-Soil Carbon Transfer in the Rhizosphere

High diversity of root-associated fungi isolated from three epiphytic orchids in southern Ecuador.

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The impact of life form on the architecture of orchid mycorrhizal networks in tropical forest

Plants are key contributors to ecosystem services delivered by green roofs in cities including stormwater capture, temperature regulation, and wildlife habitat As a result, current research has primarily focused on their growth in relationship to extensive green roof (e.g. substrates <15cm depth) ecosystem services. Green roofs are exposed to a variety of harsh abiotic factors such as intense solar radiation, wind, and isolation from ground-level habitats, making survival exceedingly difficult. Plants in natural habitats benefit from a variety of interactions with fungi and bacteria. These plant-microbial interactions improve mechanisms of survival and productivity; however, many green roof substrates are sterilized prior to installation and lack microbial communities with unstudied consequences for green roof plant health and subsequent survival and performance. In this paper, we present six hypotheses on the positive role of microbes in green roof applications. In natural and experimental systems, microbial interactions have been linked to plant (1) drought tolerance, (2) pathogen protection, (3) nutrient availability, (4) salt tolerance, (5) phytohormone production, and (6) substrate stabilization, all of which are desirable properties of green roof ecosystems. As few studies exist that directly examine these relationships on green roofs, we explore the existing ecological literature on these topics to unravel the mechanisms that could support more complex green roof ecosystem and lead to new insight into the design, performance, and broader applications in green infrastructure.

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The Green Roof Microbiome: Improving Plant Survival for Ecosystem Service Delivery

Some orchid species are present as epiphytes and lithophytes in the same habitat, but little is known about the differences of their mycorrhizal fungal communities. We used Coelogyne viscosa, which occurs both as an epiphyte and a lithophyte, as a study system to investigate orchid mycorrhizal fungal communities in lithophytes and epiphytes in Xishuangbanna National Nature Reserve (Yunnan Province, China). Twenty-three fungal operational taxonomic units (OTUs) from 18 sampling sites were identified. Results indicated that mycorrhizal fungal community composition was different between epi- and lithophytes. When we analyzed the Tulasnellaceae and Sebacinales communities separately, we found that the Sebacinales fungal communities were significantly different in the two growth habitats, but the Tulasnellaceae fungal communities were not. Our results provide evidence for distinct orchid mycorrhiza fungal communities depending on the growth habitat of the orchid. Consistent with some recent investigations of mycorrhizal fungus community composition, this study suggests that for one orchid, growth habitat affects mycorrhizal symbioses.

Mycorrhizal fungal diversity and community composition in a lithophytic and epiphytic orchid

Orchid-fungus interaction networks often consist of many different fungi that interact with co-occurring orchids in complex ways, but so far it remains largely unclear which processes determine network structure and both ecological and evolutionary mechanisms have been invoked to explain network architecture. In this research, we tested the hypothesis that closely related orchids associate with similar mycorrhizal fungi and vice versa by investigating the architecture of the interaction network between orchid mycorrhizal fungi (OMF) and nine co-occurring epiphytic Dendrobium species. All species grew on the bark of a single tree species (Camelia sinensis) in a traditional tea garden in China, which allowed us to assess the role of evolutionary history in determining the assembly of orchid-fungus communities without the confounding effects of environmental variation. In total, 101 different fungal operational taxonomic units (OTUs) known to be mycorrhizal in orchids were found. Most of the identified mycorrhizal OTUs were members of the Serendipitaceae (80% of all identified mycorrhizal sequences). All orchid species associated with a large number of fungi (average number of links: 31.6 ± 3.8), and orchids from the same species tended to have significantly more similar fungal partners than orchids from different species. The network of interactions was significantly nested (NODF = 41.59, p < 0.01), but not significantly compartmentalized (M = 0.26, Mrandom = 0.27). Phylogenetic analyses showed that the interaction network was not significantly affected by the phylogenies of the orchids or the fungi. Overall, these results indicate that the studied orchid species associated with multiple fungi simultaneously, and that the network of associations was built on asymmetric and weak reciprocal dependences. Associating with multiple fungi may be a successful strategy of orchids to colonize vacant sites and to increase survival of established plants in epiphytic habitats.

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Qiang Liu

Papers

Mycorrhizal fungal diversity and community composition in a lithophytic and epiphytic orchid

The impact of life form on the architecture of orchid mycorrhizal networks in tropical forest

The Architecture of the Network of Orchid–Fungus Interactions in Nine Co-occurring Dendrobium Species