Arbuscular mycorrhizal fungi enhance soil carbon sequestration in the coalfields, northwest China

Mycorrhizal inoculation enhanced tillering in field grown wheat, nutritional enrichment and soil properties

To meet food security, commercial fertilizers are available to boost wheat yield, but there are serious ill effects associated with these fertilizers. Amongst various organic alternatives, inoculating crop fields with mycorrhizal species is the most promising option. Although, mycorrhizae are known to enhance wheat yield, but how the mycorrhizae influence different yield and quality parameters of wheat, is not clear. Therefore, this study was undertaken to investigate the influence of indigenous mycorrhizal species on the growth of wheat, its nutritional status and soil properties, in repeated set of field experiments. In total 11 species of mycorrhizae were isolated from the experimental sites with Claroideoglomus, being the most dominant one. Five different treatments were employed during the present study, keeping plot size for each replicate as 6 × 2 m. Introduction of consortia of mycorrhizae displayed a significant increase in number of tillers/plant (49.5%), dry biomass (17.4%), grain yield (21.2%) and hay weight (16.7%). However, there was non-significant effect of mycorrhizal inoculation on 1,000 grains weight. Moreover, protein contents were increased to 24.2%. Zinc, iron, phosphorus and potassium concentrations were also increased to 24%, 21%, 30.9% and 14.8%, respectively, in wheat grains. Enhancement effects were also noted on soil fertility such as soil organic carbon % age, available phosphorus and potassium were increased up to 64.7%, 35.8% and 23.9%, respectively. Herein, we concluded that mycorrhizal introduction in wheat fields significantly increased tillering in wheat and this increased tillering resulted in overall increase in wheat biomass/yield. Mycorrhizae also enhanced nutritional attributes of wheat grains as well as soil fertility. The use of mycorrhizae will help to reduce our dependance on synthetic fertilizers in sustainable agriculture.

Arbuscular Mycorrhizal Fungi Response on Soil Phosphorus Utilization and Enzymes Activities in Aerobic Rice under Phosphorus-Deficient Conditions

The prominence of arbuscular mycorrhizal fungi (AMF) in sustainable rice production has long been recognized. However, there is little information about AMF response in aerobic rice cultivation under phosphorus (P)-deficient conditions. The aim of this experiment was to compare and determine the preeminent AMF effects on rice mycorrhizal colonization, responsiveness, P utilization, and different growth-promoting traits under P-deficient conditions. Different AMF genera viz. (Funneliformis sp., Rhizophagus sp., Glomus sp., Acaulospora sp., and Claroideoglomus sp.) in four different aerobic rice varieties developed by ICAR-NRRI, India (CR Dhan 201, CR Dhan 204, CR Dhan 205, and CR Dhan 207) were investigated using the check P-susceptible variety (IR 36) and the P-tolerant variety (Kasalath IC459373). Data analyzed through linear modeling approaches and bivariate associations found that AMF colonization was highly correlated with soil enzymes, particularly fluorescein diacetate (FDA) and plant P uptake. The microbial biomass carbon (MBC) and FDA content were significantly changed among rice varieties treated with AMF compared to uninoculated control. Out of four different rice varieties, CR Dhan 207 inoculated with AMF showed higher plant P uptake compared to other varieties. In all the rice varieties, AMF colonization had higher correlation coefficients with soil enzymes (FDA), MBC, and plant P uptake than uninoculated control. The present study indicates that AMF intervention in aerobic rice cultivation under P-deficient conditions significantly increased plant P uptake, soil enzymes activities and plant growth promotion. Thus, the information gathered from this study will help us to develop a viable AMF package for sustainable aerobic rice cultivation.

AMF Inoculum Enhances Crop Yields of Zea mays L. 'Chenghai No. 618' and Glycine max L. 'Zhonghuang No. 17' without Disturbing Native Fugal Communities in Coal Mine Dump

For the agricultural development of dumps, increase in land use efficiency and protection of food security, to verify the safety, efficacy and sustainability of field-applied arbuscular mycorrhizal fungi (AMF) inoculum, and to exclude the risk of potential biological invasion, in this study, we determined the effect of AMF inoculation and intercropping patterns (maize-soybean) on the temporal dynamics of soil parameters, native AMF communities and crop yields. AMF communities were analyzed using Illumina MiSeq. A total of 448 AMF operational taxonomic units (OTUs) belonging to six genera and nine families were identified. AMF inoculation treatment significantly improved the yield of intercropping maize and increased the content of available phosphorus. AMF diversity was significantly influenced by cropping pattern and growth stage, but not by the inoculation treatment. Inoculation altered the AMF community composition in the early growth stage and facilitated a more complex AMF network in the early and late growth stages. These results indicate that AMF inoculation affects native AMF only in the early stage, and its impact on yield may be the consequence of cumulative effects due to the advantages of plant growth and nutrient uptake in the early stage.

Hedgerows increase the diversity and modify the composition of arbuscular mycorrhizal fungi in Mediterranean agricultural landscapes

Sustainable agriculture is essential to address global challenges such as climate change and biodiversity loss. Hedgerows enhance aboveground biodiversity and provide ecosystem services, but little is known about their impact on soil biota. Arbuscular mycorrhizal (AM) fungi are one of the key components of belowground biodiversity. We compared the diversity and composition of AM fungal communities at four farmland sites located in Central Spain, where 132 soil samples in total were collected to assess soil physical and chemical properties and the AM fungal communities. We compared the richness (number of AM fungal taxa), taxonomic, functional, and phylogenetic diversity, and structure of the AM fungal communities across three farmland habitat types, namely hedgerows, woody crops (olive groves and vineyard), and herbaceous crops (barley, sunflower, and wheat). Our results showed positive effects of hedgerows on most diversity metrics. Almost 60% of the AM fungal taxa were shared among the three farmland habitat types. Hedgerows increased AM fungal taxonomic richness (31%) and alpha diversity (25%), and especially so compared to herbaceous crops (45% and 28%, respectively). Hedgerows harbored elevated proportions of AM fungi with non-ruderal life-history strategies. AM fungal communities were more similar between hedgerows and woody crops than between hedgerows and adjacent herbaceous crops, possibly because of differences in tillage and fertilization. Unexpectedly, hedgerows reduced phylogenetic diversity, which might be related to more selective associations of AM fungi with woody plants than with herbaceous crops. Overall, the results suggest that planting hedgerows contributes to maintain belowground diversity. Thus, European farmers should plant more hedgerows to attain the goals of the EU Biodiversity Strategy for 2030.

Biotechnology of Microorganisms from Coal Environments: From Environmental Remediation to Energy Production

Simple Summary

Despite the wide perception that coal environments are extreme habitats, they harbor resident microbial communities. Coal-associated habitats, such as coal mine areas/drainages, spoil heaps, and coalbeds, are defined as complex ecosystems with indigenous microbial groups and native microecological networks. Resident microorganisms possess rich functional potentials and profoundly shape a range of biotechnological processes in the coal industry, from production to remediation.

Abstract

It was generally believed that coal sources are not favorable as live-in habitats for microorganisms due to their recalcitrant chemical nature and negligible decomposition. However, accumulating evidence has revealed the presence of diverse microbial groups in coal environments and their significant metabolic role in coal biogeochemical dynamics and ecosystem functioning. The high oxygen content, organic fractions, and lignin-like structures of lower-rank coals may provide effective means for microbial attack, still representing a greatly unexplored frontier in microbiology. Coal degradation/conversion technology by native bacterial and fungal species has great potential in agricultural development, chemical industry production, and environmental rehabilitation. Furthermore, native microalgal species can offer a sustainable energy source and an excellent bioremediation strategy applicable to coal spill/seam waters. Additionally, the measures of the fate of the microbial community would serve as an indicator of restoration progress on post-coal-mining sites. This review puts forward a comprehensive vision of coal biodegradation and bioprocessing by microorganisms native to coal environments for determining their biotechnological potential and possible applications.

Does Commercial Inoculation Promote Arbuscular Mycorrhizal Fungi Invasion?

Interventions with commercial inoculants have the potential to reduce the environmental footprint of agriculture, but their indiscriminate deployment has raised questions on the unintended consequences of microbial invasion. In the absence of explicit empirical reports on arbuscular mycorrhizal fungi (AMF) invasion, we examine the present framework used to define AMF invasion and offer perspectives on the steps needed to avoid the negative impacts of AMF invasion. Although commercial AMF isolates are potential invaders, invasions do not always constitute negative impacts on native community diversity and functions. Instead, the fates of the invading and resident communities are determined by ecological processes such as selection, drift, dispersal, and speciation. Nevertheless, we recommend strategies that reduce overdependence on introduced inoculants, such as adoption management practices that promote the diversity and richness of indigenous AMF communities, and the development of native propagules as a supplement to commercial AMF in applicable areas. Policies and regulations that monitor inoculant value chains from production to application must be put in place to check inoculant quality and composition, as well as the transport of inoculants between geographically distant regions.

Effect of crop cultivation on the soil carbon stock in mine dumps of the Loess Plateau, China

In the ecological restoration of mine dumps, soil carbon stock (SCS) improvement is an important issue. The type of land use and management approach taken can have a great influence on this issue. On the Loess Plateau, different crops have been cultivated on reclaimed land; however, the effect of long-term crop cultivation on SCS is poorly understood. To address this issue, a field investigation of mine dumps was performed at the Kee Open Pit Mine in Shanxi Province, China. Four sites utilizing different land management methods were analyzed: no reclamation (NR), reclamation with no crop cultivation (NC), and reclamation followed by 11 or 27 years crop cultivation (RC-11 and RC-27, respectively). SCS, associated soil properties (total nitrogen (TN), total phosphorus (TP), total potassium (TK), moisture content (MoiC), and pH), plant community (species composition, plant diversity, and traits), and microbial community operational taxonomic units (OTUs) of fungi and bacteria were determined by field investigation and laboratory analysis. Redundancy analysis was used to show the relationship between SCS and other environmental variables. Results varied by soil depth. At the depth range of 0-20 cm, the SCS of RC-11 was significantly greater compared to that in NR and NC, by 14.64- and 2.25-fold, respectively; whereas compared to RC-27, it was higher by 52.78%. At the depth of 20-40 cm, NC has the largest SCS; the SCS of RC-27 was the lowest, which was less compared to that in NC by 43.64%. Redundancy analysis showed a positive relationship between the SCS and TN, TP, MoiC, as well as average plant coverage, while the bacterial OTUs were negatively related with the SCS. This research suggests the potential of mine dumps for crop cultivation, which could improve the SCS of the mining area on the Loess Plateau.

Native forests but not agroforestry systems preserve arbuscular mycorrhizal fungal species richness in southern Ethiopia

The rapid conversion of native forests to farmland in Ethiopia, the cradle of biodiversity, threatens the diversity of the arbuscular mycorrhizal fungi (AMF) pivotal to plant nutrition and carbon sequestration. This study aimed to investigate the impact of this land-use change on the AMF species composition and diversity in southern Ethiopia. Soil samples were collected from nine plots in each of three land-use types: native forest, agroforestry, and khat monocropping. The plots of the three land-use types were located adjacent to each other for each of the nine replicates. Three 10 × 10m subplots per plot were sampled. AMF spores were extracted from the soil samples, spore densities were determined, and species composition and diversity were evaluated through morphological analysis. Both spore density and species richness were statistically significantly higher in the native forest than in the agroforestry plots with no clear difference to khat, whereas the true diversity (exponential of Shannon-Wiener diversity index) did not differ among the three land-use types due to high evenness among the species in agroforestry. In total, 37 AMF morphotypes belonging to 12 genera in Glomeromycota were found, dominated by members of the genera Acaulospora and Glomus. The highest isolation frequency index (78%) was recorded for Acaulospora koskei from native forest. Consequently, the agroforestry system did not appear to aid in preserving the AMF species richness of native forests relative to perennial monocropping, such as khat cultivation. In contrast, the native forest areas can serve as in situ genetic reserves of mycorrhizal symbionts adapted to the local vegetative, edaphic, and microbial conditions.

The potential of arbuscular mycorrhizal fungi in C cycling: a review

Arbuscular mycorrhizal fungi (AMF) contribute predominantly to soil organic matter by creating a sink demand for plant C and distributing to below-ground hyphal biomass. The extra-radical hyphae along with glomalin-related soil protein significantly influence the soil carbon dynamics through their larger extent and turnover period need to discuss. The role of AMF is largely overlooked in terrestrial C cycling and climate change models despite their greater involvement in net primary productivity augmentation and further accumulation of this additional photosynthetic fixed C in the soil. However, this buffering mechanism against elevated CO₂ condition to sequester extra C by AMF can be described only after considering their potential interaction with other microbes and associated mineral nutrients such as nitrogen cycling. In this article, we try to review the potential of AMF in C sequestration paving the way towards a better understanding of possible AMF mechanism by which C balance between biosphere and atmosphere can be moved forward in more positive direction.

Simulation of Mining-Induced Ground Damage Using Orthogonal Experiments to Determine Key Parameters of Super-Large Coalface: A Case Study in Shendong Coalfield in China

High-strength mining of super-large coalfaces in the Shendong coalfield causes significant damage to the ground surface. To study the key parameters of undermined coalfaces that affect ground damage, 25 numerical simulation models were designed using an orthogonal experimental method based on the geological and mining conditions of the Bulianta Mine. In the orthogonal design, four factors (the lengths in both the dip and strike directions, the thickness and the mining speed of the coalface) were considered, with five levels designed for each factor. The subsidence displacements and deformations caused by the excavation were then simulated and verified using field surveying data. A damage extent index (DEI) was introduced and used to assess the extent of global ground damage caused by each simulative excavation. Analysis of variance (ANOVA) method was then employed to determine the key parameters of the coalface that significantly influence the ground damage. It was found that the coalface dip length and thickness and the coalface thickness can be regarded as the key parameters for ground objects of building and timberland, respectively. This research provides theoretical and technical support for the coordinated exploitation of resources and environments in Shendong and other similar, ecologically fragile coalfields.

Formation of Common Mycorrhizal Networks Significantly Affect Plant Biomass and Soil Properties of the Neighboring Plants under Various Nitrogen Levels

Common mycorrhizal networks (CMNs) allow the transfer of nutrients between plants, influencing the growth of the neighboring plants and soil properties. Cleistogene squarrosa (C. squarrosa) is one of the most common grass species in the steppe ecosystem of Inner Mongolia, where nitrogen (N) is often a key limiting nutrient for plant growth, but little is known about whether CMNs exist between neighboring individuals of C. squarrosa or play any roles in the N acquisition of the C. squarrosa population. In this study, two C. squarrosa individuals, one as a donor plant and the other as a recipient plant, were planted in separate compartments in a partitioned root-box. Adjacent compartments were separated by 37 µm nylon mesh, in which mycorrhizal hyphae can go through but not roots. The donor plant was inoculated with arbuscular mycorrhizal (AM) fungi, and their hyphae potentially passed through nylon mesh to colonize the roots of the recipient plant, resulting in the establishment of CMNs. The formation of CMNs was verified by microscopic examination and 15N tracer techniques. Moreover, different levels of N fertilization (N0 = 0, N1 = 7.06, N2 = 14.15, N3 = 21.19 mg/kg) were applied to evaluate the CMNs' functioning under different soil nutrient conditions. Our results showed that when C. squarrosa-C. squarrosa was the association, the extraradical mycelium transferred the 15N in the range of 45-55% at different N levels. Moreover, AM fungal colonization of the recipient plant by the extraradical hyphae from the donor plant significantly increased the plant biomass and the chlorophyll content in the recipient plant. The extraradical hyphae released the highest content of glomalin-related soil protein into the rhizosphere upon N2 treatment, and a significant positive correlation was found between hyphal length and glomalin-related soil proteins (GRSPs). GRSPs and soil organic carbon (SOC) were significantly correlated with mean weight diameter (MWD) and helped in the aggregation of soil particles, resulting in improved soil structure. In short, the formation of CMNs in this root-box experiment supposes the existence of CMNs in the typical steppe plants, and CMNs-mediated N transfer and root colonization increased the plant growth and soil properties of the recipient plant.

The extraradical proteins of Rhizophagus irregularis: A shotgun proteomics approach

Arbuscular Mycorrhizal fungi (AMF, Glomeromycota) form obligate symbiotic associations with the roots of most terrestrial plants. Our understanding of the molecular mechanisms enabling AMF propagation and AMF-host interaction is currently incomplete. Analysis of AMF proteomes could yield important insights and generate hypotheses on the nature and mechanism of AMF-plant symbiosis. Here, we examined the extraradical mycelium proteomic profile of the arbuscular mycorrhizal fungus Rhizophagus irregularis grown on Ri T-DNA transformed Chicory roots in a root organ culture setting. Our analysis detected 529 different peptides that mapped to 474 translated proteins in the R. irregularis genome. R. irregularis proteome was characterized by a high proportion of proteins (9.9 % of total, 21.4 % of proteins with functional prediction) mediating a wide range of signal transduction processes, e.g. Rho1 and Bmh2, Ca-signaling (calmodulin, and Ca channel protein), mTOR signaling (MAP3K7, and MAPKAP1), and phosphatidate signaling (phospholipase D1/2) proteins, as well as members of the Ras signaling pathway. In addition, the proteome contained an unusually large proportion (53.6 %) of hypothetical proteins, the majority of which (85.8 %) were Glomeromycota-specific. Forty-eight proteins were predicted to be surface/membrane associated, including multiple hypothetical proteins of yet-unrecognized functions. However, no evidence for the overproduction of specific proteins, previously implicated in promoting soil health and aggregation was obtained. Finally, the comparison of R. irregularis proteome to previously published AMF proteomes identified a core set of pathways and processes involved in AMF growth. We conclude that R. irregularis growth on chicory roots requires the activation of a wide range of signal transduction pathways, the secretion of multiple novel hitherto unrecognized Glomeromycota-specific proteins, and the expression of a wide array of surface-membrane associated proteins for cross kingdom cell-to-cell communications.

Presidential address: recent advance of mycorrhizal research in China

I am honoured to address as the seventh president of the Mycological Society of China. Mycorrhizal research has a long history in China, including taxonomy, diversity, ecology, molecular biology, and application. Particularly in the past four decades, great progress in mycorrhizal field has been made by Chinese mycologists and ecologists. In this paper, through my own experience, I summarised the main and important advance of recent mycorrhizal researches in terms of mycorrhizal fungal diversity, community, responses to global environmental changes, molecular biology, and function in China. Some perspectives are also proposed for future mycorrhizal studies in China.