Fungal Root Research Articles

Studies on the arbuscular mycorrhizal fungal association in the plant species of theerthamalai hills, western ghats of dharmapuri district tamilnadu, india

The present study to investigate the arbuscular mycorrhizal fungal root colonization and spore population of some medicinal plants species at Theerthamalai hills Western Ghats of Dharmapuri district, Tamil Nadu. Root and rhizosphere soil samples were collected during the month of August, 2010-March, 2011. From the surface to 20 cm depth as well as pH were also measured. Totally 42 plant species belonging to 24 families recovered Arbuscular mycorrhizal fungal spore and root colonization. The results of the present study arbuscular mycorrhizal fungal spore population in the rhizosphere soil and root colonization of all the plant species. The maximum spore population was found in the rhizosphere soil samples of the plant species Leucas aspera (386/100g of soil) which belongs to the family Lamiaceae and lowest spore population was observed in the Wrightia tinctoria (117/100g of soil) belongs to Apocyanaceae. The maximum AM fungal infection was found in roots of Cassia auriculata (63%) belongs to the family Fabaceae, while the lowest AM fungal association was found in the root of Achyranthes aspera (17%) belongs to the family Amaranthaceae. A total of 24 AM fungal species belonging to 4 genera were recorded from the rhizosphere soil samples of this study region. Among these genus Glomus was dominant had seen in rhizosphere soil samples in all the medicinal plant species.

Fungal root colonization and arbuscular mycorrhizal fungi diversity in soils of grasslands with different mowing intensities

Grasslands are among the most dynamic and threatened plant communities, largely due to their dependence on management that has changed in recent decades. The intensity of human-induced disturbances (primarily removal of plant biomass by various methods) has decreased, leading to changes in plant species composition and declines in plant diversity in these communities. So far, no studies have shown how mowing affects fungal communities in both roots and soils and their relation with plant community parameters and soil chemical properties in different grassland types. We thus compared the impact of mowing intensity (low, moderate, high) on root colonization by common root-inhabiting fungi, namely arbuscular mycorrhizal fungi (AMF), dark septate endophytes (DSE), and Olpidium spp., as well as on AMF spore number, species richness and composition in soils for three seasons (spring, summer, autumn), in grasslands differing in soil moisture (wet, moderately wet, and dry). Mowing intensity had no effect on the fungal root colonization. The number of AMF spores and species, and AMF species composition did not differ between types of management as well. However, most of the fungal parameters in roots and soils varied across the types of grassland and/or seasons. Our results suggest that AMF, DSE, and Olpidium spp. colonization of plants as well as AMF diversity in soils in the studied grasslands are resilient to the mowing disturbance. This may be due to the low impact of the management on plant species richness and soil chemical properties, as well as the adaptation of these fungal communities to recurrent human-induced disturbances in semi-natural habitats.

Effect of arbuscular mycorrhizal fungi in roots on antioxidant enzyme activity in leaves of Robinia pseudoacacia L. seedlings under elevated CO2 and Cd exposure

Arbuscular mycorrhizal fungi (AMF) are easily influenced by increasing atmospheric CO2 concentration and heavy metals including cadmium (Cd), which can regulate antioxidant enzyme in host plants. Although the effect of AMF under individual conditions such as elevated CO2 (ECO2) and Cd on antioxidant enzyme in host plants has been reported widely, the effect of AMF under ECO2 + Cd receives little attention. In this study, a pot experiment was conducted to study the effect of AMF community in roots on superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities in leaves of 135-d Robinia pseudoacacia L. seedlings under ECO2 + Cd. The activities of SOD and CAT increased and POD activity and the richness and diversity of AMF community decreased under ECO2 + Cd relative to Cd alone. The richness and diversity of AMF were negatively related to Cd content in roots and leaves. The richness and OTUs of AMF community positively and AMF gene abundance negatively affected POD activity under the combined treatments. Superoxide dismutase and POD activities were negatively and positively related to Archaeospora and Scutellospora, respectively, under ECO2 + Cd. Cadmium in roots and leaves was negatively and significantly related to Glomus, Scutellospora, and Claroideoglomus abundance under ECO2 + Cd. Overall, AMF diversity and Archaeospora and Scutellospora in roots significantly influenced SOD, POD, and CAT activities. The response of AM symbiosis to ECO2 might regulate antioxidant capacity in host plants upon Cd exposure. Glomus, Scutellospora, and Claroideoglomus might be applied to phytoremediation of Cd-contaminated soils.

Plant neighbours can make or break the disease transmission chain of a fungal root pathogen.

Summary Biodiversity can reduce or increase disease transmission. These divergent effects suggest that community composition rather than diversity per se determines disease transmission. In natural plant communities, little is known about the functional roles of neighbouring plant species in belowground disease transmission.Here, we experimentally investigated disease transmission of a fungal root pathogen (Rhizoctonia solani) in two focal plant species in combinations with four neighbour species of two ages. We developed stochastic models to test the relative importance of two transmission‐modifying mechanisms: (1) infected hosts serve as nutrient supply to increase hyphal growth, so that successful disease transmission is self‐reinforcing; and (2) plant resistance increases during plant development.Neighbouring plants either reduced or increased disease transmission in the focal plants. These effects depended on neighbour age, but could not be explained by a simple dichotomy between hosts and nonhost neighbours. Model selection revealed that both transmission‐modifying mechanisms are relevant and that focal host–neighbour interactions changed which mechanisms steered disease transmission rate.Our work shows that neighbour‐induced shifts in the importance of these mechanisms across root networks either make or break disease transmission chains. Understanding how diversity affects disease transmission thus requires integrating interactions between focal and neighbour species and their pathogens.

First report of Eutypella species associated with dying cotton (Gossypium hirsutum L.)

A rapid increase in the number of Gossypium hirsutum L. plants suddenly wilting and dying in a commercial cotton field in Central Queensland initiated this study. The aim was to characterise fungal species recovered from discoloured vascular tissue of dead plants and determine if they contributed to their death. Isolations were consistently dominated by one fungus based on culture morphology. Identification was established on sequences of the internal transcribed spacer (ITS) region of ribosomal DNA and revealed that the isolates all belong to Diatrypaceae, with high homology to Eutypella scoparia. Further analyses showed that there were two distinct Eutypella species present in the isolates, which are quite different from E. scoparia from the sequence dissimilarity due to the presence of ITS1 and ITS2 insertions. In diseased root samples, community profiling showed two operational taxonomic units (OTUs) related to E. scoparia were the most abundant fungi accounting for 45 to 99% of all sequences. Pathogenicity tests showed that a Eutypella isolate when inoculated into the stem of healthy G. hirsutum using two inoculation methods caused cankerous growth and necrosis of vascular tissue, typical of trunk disease. The fungus caused a red—brown streaking of the vascular tissue like that observed in diseased field plants. This study shows that the fungal isolates, which form a distinct group within the Eutypella, are associated with the root and stem of dying G. hirsutum and were the dominant fungi of diseased roots. This is the first known case of Eutypella affecting cotton worldwide and is considered an expansion of this genus’ host range.

Arbuscular Mycorrhizal Communities in the Roots of Sago Palm in Mineral and Shallow Peat Soils

Communities of arbuscular mycorrhizal fungi (AMF) in plant roots improve host plant growth. In this study, AMF communities in the roots of the sago palm (Metroxylon sagu Rottb.) were investigated in mineral soil (MS) and shallow peat soil (SPS) in Sarawak, Malaysia. MS exhibited lower moisture content (MS, 38.1; SPS, 79.8%), higher pH (H2O) (MS, 4.6; SPS, 4.1), higher soil bulk density (MS, 1.03; SPS, 0.20 g cm−3), and higher nitrogen content (MS, 16.9; SPS, 2.7 kg m−3) than SPS at the same soil depth, while the phosphorus (P) content (Bray II) (MS, 1.6; SPS, 1.9 g P2O5 m−3) was similar. The AMF colonization rate was significantly lower in SPS (39.2 ± 12.5%) than in MS (73.2 ± 4.6%). The higher number of AMF operational taxonomic units (OTUs) was detected by amplicon sequencing of the partial small-subunit rRNA gene (MS, 78; SPS, 50). A neighbor-joining tree of obtained OTUs revealed that they belonged to Acaulosporaceae, Ambisporaceae, Claroideoglomeraceae, Gigasporaceae, and Glomeraceae. The lower abundance and diversity of AMF in SPS are possibly caused by abiotic factors, including soil physicochemical properties. Glomus and Acaulospora species detected in SPS might have strong tolerance against acidity and high soil moisture content.

Grazing Intensity Rather than Host Plant's Palatability Shapes the Community of Arbuscular Mycorrhizal Fungi in a Steppe Grassland.

Arbuscular mycorrhizal fungi (AMF) are the predominant type of mycorrhizal fungi in roots and rhizosphere soil of grass species worldwide. Grasslands are currently experiencing increasing grazing pressure, but it is not yet clear how grazing intensity and host plant grazing preference by large herbivores interact with soil- and root-associated AMF communities. Here, we tested whether the diversity and community composition of AMF in the roots and rhizosphere soil of two dominant perennial grasses, grazed differently by livestock, change in response to grazing intensity. We conducted a study in a long-term field experiment in which seven levels of field-manipulated grazing intensities were maintained for 13 years in a typical steppe grassland in northern China. We extracted DNA from the roots and rhizosphere soil of two dominant grasses, Leymus chinense (Trin.) Tzvel. and Stipa grandis P. Smirn, with contrasting grazing preference by sheep. AMF DNA from root and soil samples was then subjected to molecular analysis. Our results showed that AMF α-diversity (richness) at the virtual taxa (VT) level varied as a function of grazing intensity. Different VT showed completely different responses along the gradient, one increasing, one decreasing, and others showing no response. Glomeraceae was the most abundant AMF family along the grazing gradient, which fits well with the theory of disturbance tolerance of this group. In addition, sheep-grazing preference for host plants did not explain much of the variation in AMF α-diversity. However, the two grass species exhibited different AMF community composition in their roots and rhizosphere soils. Roots exhibited a lower α-diversity and higher β-diversity within the AMF community than soils. Overall, our results suggest that long-term grazing intensity might have changed the abundance of functionally diverse AMF taxa in favor of those with disturbance-tolerant traits. We suggest our results would be useful in informing the choice of mycorrhizal fungi indicator variables when assessing the impacts of grassland management choices on grassland ecosystem functioning.

Fusarium temperatum shows a hemibiotrophic infection process and differential pathogenicity over different maize breeds from Mexico

AbstractThe genus Fusarium contains several species that cause diseases, such as drowning and wilting, in cultivable plants. Fusarium temperatum has been included in the Giberella fujikuroi complex and has been reported as a devastating pathogen for maize in Asia, Europe and South America. In Mexico, maize is one of the most important crops, so we consider it of great importance to describe the infection process of F. temperatum on maize plantlets and the susceptibility of several breeds of maize. We use in vivo assays to determine the infectivity of 6 maize breeds from Mexico. The most resistant breed was Pepitilla with less than 10 percent of damage, while Harinoso de 8, Tuxpeño and Tepecintle showed moderate resistance, while Reventador and Zapata 2 showed the most extensive damage. Because of its susceptibility, Zapata 2 was used to follow the infection process of F. temperatum. To follow the fungus in the infected roots we use a transformed strain that expresses GFPs. We found that the fungus directly penetrates the root tissue without forming an appressorium. We were able to establish a hemibiotrophic infection pattern for F. temperatum (biotrophic stage: 5–10 dpi; transition stage: 15 dpi; necrotrophic stage: 20 dpi). Our results described that F. temperatum presents a hemibiotropic infection pattern and suggests the presence of maize breeds in Mexico that have natural resistance to F. temperatum.

The fungal root endophyte Serendipita vermifera displays inter-kingdom synergistic beneficial effects with the microbiota in Arabidopsis thaliana and barley

Plant root-associated bacteria can confer protection against pathogen infection. By contrast, the beneficial effects of root endophytic fungi and their synergistic interactions with bacteria remain poorly defined. We demonstrate that the combined action of a fungal root endophyte from a widespread taxon with core bacterial microbiota members provides synergistic protection against an aggressive soil-borne pathogen in Arabidopsis thaliana and barley. We additionally reveal early inter-kingdom growth promotion benefits which are host and microbiota composition dependent. Using RNA-sequencing, we show that these beneficial activities are not associated with extensive host transcriptional reprogramming but rather with the modulation of expression of microbial effectors and carbohydrate-active enzymes.

Evaluation of yield and resistance of sugar beet cultivars to fungal root rots under drought stress

Evaluation of yield and resistance of sugar beet cultivars to fungal root rots under drought stress

Untangling the Pea Root Rot Complex Reveals Microbial Markers for Plant Health.

Plant health is recognised as a key element to ensure global food security. While plant breeding has substantially improved crop resistance against individual pathogens, it showed limited success for diseases caused by the interaction of multiple pathogens such as root rot in pea (Pisum sativum L.). To untangle the causal agents of the pea root rot complex and determine the role of the plant genotype in shaping its own detrimental or beneficial microbiome, fungal and oomycete root rot pathogens, as well as previously identified beneficials, i.e., arbuscular mycorrhizal fungi (AMF) and Clonostachys rosea, were qPCR quantified in diseased roots of eight differently resistant pea genotypes grown in four agricultural soils under controlled conditions. We found that soil and pea genotype significantly determined the microbial compositions in diseased pea roots. Despite significant genotype x soil interactions and distinct soil-dependent pathogen complexes, our data revealed key microbial taxa that were associated with plant fitness. Our study indicates the potential of fungal and oomycete markers for plant health and serves as a precedent for other complex plant pathosystems. Such microbial markers can be used to complement plant phenotype- and genotype-based selection strategies to improve disease resistance in one of the world’s most important pulse crops of the world.

Mouldy Matriarchs and Dangerous Daughters

Mouldy Matriarchs and Dangerous Daughters

Endophytic fungi in roots of native orchids of rupestrian grasslands (campos rupestres) in Serra do Cipó, Brazil

Root endophytic fungi are essential to the life cycle of orchids. Many of them act as growth promoters of the host plant and mycorrhizal endophytes are indispensable to seed germination. This study aimed to evaluate the cultivable endophytic fungal richness of five native orchids of rupestrian grasslands (campos rupestres) in Serra do Cipó, Brazil. Healthy roots were sampled and the endophytes isolated, from which total DNA was extracted and the Internal Transcribed Spacer (ITS) region amplified and sequenced. Analysis of 32 fungal sequences permitted the identification of 25 species of the phyla Ascomycota and Basidiomycota. Nine isolates belonged to the Basidiomycota genera Sebacina Tul. & C. Tul. and Tulasnella J. Schröt., which contain important mycorrhizal endophytes of orchids. Same fungal species were obtained from different orchids growing on distinct substrates. Fungal molecular identification indicates high endophyte richness supporting the life cycle of orchids in rupestrian grasslands.

Drought induces shifts in soil fungal communities that can be linked to root traits across 24 plant species.

Root traits respond to drought in a species-specific manner, but little is known about how soil fungal communities and root traits respond to drought in concert. In a glasshouse experiment, we determined the response of soil pathogens, saprotrophs, and mutualistic and all fungi associated with the roots of 24 plant species subjected to drought. At harvest, soil fungal communities were characterized by sequencing. Data on root traits were extracted from a previously published work. Differences in fungal beta diversity between drought and control were plant species specific. For some species, saprotrophic fungi increased in relative abundance and richness with drought, whereas mutualistic fungi showed the opposite pattern. Community structure of pathogenic fungi was plant species specific but was slightly affected by drought. Pathogen composition was correlated with specific root surface area and root:shoot, saprotroph abundance with root tissue density, whereas mutualist composition was correlated with root:shoot. All these were the fungal attributes that best predicted shoot mass. Fungal response to drought depended highly on the fungal group and was related to root trait adjustments to water scarcity. This provides new insights into the role that root trait adjustments to drought may have in modulating plant-fungus interactions in grasslands ecosystems.

Function and Characterization of Fungal Communities in Chestnut Soils (Castanea crenata) of Kansai Region, Japan

Chestnut (Castanea crenata) is an important fruit crop in Japan, grown under three cultivation systems in Kansai region, which succumb to fungal root disease pathogens. The fungal community in soils of chestnut in these cultivation systems were characterized along with the potential of soil bacterial species as biological control agent against these root-invading fungi. Bacteria from the chestnut soil rhizosphere were identified and their ability to suppress diseases in vitro was evaluated. Bacteria DAC17225011 and DAC17225014 showed 99% similarity to Bacillus aryabhattai and Pseudomonas frederiksbergensis, respectively, which could suppress the growth of Armilaria mellea and Phytophtora cambivora, respectively, in in vitro conditions. The assay in vivo indicated the positive effect of these bacteria on the reduction of disease infection spots in chestnut roots; however, no visible symptoms were detected aboveground. For microbial community analysis, chestnut soil was sampled from four locations (Wachi, Ayabe, Fukuchiyama and Sasayama) considering three management systems, conventional, organic and wild. The amplicon from the ITS region (The genomic library of the fungal detection in soils) was sequenced by Illumina MiSeq 250bp and used to analyze the fungal community in the sampled soil. Nectriaceae, which contains pathogenic fungi, was very common in all samples, but lower in wild areas. Ceratobasidiacea was also higher in conventional areas. For the symbiotic families, Hypocraceae and Russulaceae were typical in wild soils, whereas Amanitaceae was found in organic soils. The fungal community was clearly distinct in the wild system, differing from conventional and organic systems.

High temperature associated microRNAs and their potential roles in mediating heat tolerance in the leaf of banana inoculated with Serendipita indica

ABSTRACT Serendipita indica (S. indica) is an endophytic root fungus that sustains the growth and enhances tolerance of plants to biotic and abiotic stresses. However, little is known on the symbiosis mediated high temperature stress (HT) tolerance regulated at microRNAs (miRNAs) level. In this study, we have elucidated the impact of miRNAs in regulating the S. indica-mediated heat tolerance in the leaves of ‘Tianbao’ banana (Musa acuminata cv.). The small RNA (sRNA) sequence analysis of the leaves of ‘Tianbao’ banana inoculated and exposed to HT of 45°C established a set of 278 differentially abundant miRNAs in response to HT stress. These included 185 known miRNAs differentially expressed (DE) and 93 novel miRNAs. GO and KEGG analysis showed that the DE miRNAs were significantly associated with nutrient sources uptake, secondary metabolism, growth regulators, auxin-responsive factor, signal transduction pathways. In summary, our study revealed that miRNA play important regulatory roles during the banana-HT tolerance by regulating the genes involved in heat shock protein, peroxidase, transcription factor, phenylalanine, sucrose synthase, protein kinase, 7-hydroxymethyl chlorophyll. Our result unravelled a framework for future functional analysis of selected miRNAs and their targets in response to HT stress, which may contribute towards the future development of S. indica application to plants.

Deep learning-based quantification of arbuscular mycorrhizal fungi in plant roots.

Soil fungi establish mutualistic interactions with the roots of most vascular land plants. Arbuscular mycorrhizal (AM) fungi are among the most extensively characterised mycobionts to date. Current approaches to quantifying the extent of root colonisation and the abundance of hyphal structures in mutant roots rely on staining and human scoring involving simple yet repetitive tasks which are prone to variation between experimenters. We developed Automatic Mycorrhiza Finder (AMFinder) which allows for automatic computer vision-based identification and quantification of AM fungal colonisation and intraradical hyphal structures on ink-stained root images using convolutional neural networks. AMFinder delivered high-confidence predictions on image datasets of roots of multiple plant hosts (Nicotiana benthamiana, Medicago truncatula, Lotus japonicus, Oryza sativa) and captured the altered colonisation in ram1-1, str, and smax1 mutants. A streamlined protocol for sample preparation and imaging allowed us to quantify mycobionts from the genera Rhizophagus, Claroideoglomus, Rhizoglomus and Funneliformis via flatbed scanning or digital microscopy, including dynamic increases in colonisation in whole root systems over time. AMFinder adapts to a wide array of experimental conditions. It enables accurate, reproducible analyses of plant root systems and will support better documentation of AM fungal colonisation analyses. AMFinder can be accessed at https://github.com/SchornacklabSLCU/amfinder.

Seasonal dynamics of the pink root fungus (Setophoma terrestris) in rhizosphere soil: Effect of crop species and rotation

AbstractSetophoma terrestris, a ubiquitous inhabitant of soil, causes pink root rot in various crops. In the present study, the density of S. terrestris was estimated by quantitative real‐time PCR in onion and non‐onion fields of Hokkaido, the northernmost island of Japan. Three‐year observations in monoculture and rotation fields demonstrated that the fungus grew significantly from the third year onwards, and declined in fields planted with poor hosts (e.g., sugar beet and soybean) that produced few or no chlamydospores of S. terrestris. Seasonal analysis revealed that the population of S. terrestris consistently increased when the tops of onions fell over in summer, which is when root activity declines. However, the soil inoculum potential estimated by a seedling bioassay showed distinct seasonal patterns, which rose from post‐harvest in winter and remained high until the subsequent planting in spring. Detailed surveys on depth distribution in an onion field detected a high population of S. terrestris in the effective layer (10–30 cm deep) but not below the hardpan (40 cm), implying that the fungus is intimately associated with roots. These results indicate that the proliferation of the fungus is closely related to root senescence and that over‐wintered propagules play an important role in primary infections, affecting disease severity. The present study shows that the temporal dynamics of S. terrestris depend exclusively on the activity of infecting roots and provides circumstantial evidence on the deleterious impact of monoculture on crop production.

A Review on Mycorrhizae and Related Endophytic Fungi as Potential Sources of Enzymes for the Bio-Economy

Ericoid mycorrhizal (ERM) fungi and related fungal root endophytes do form symbiotic associations with roots of ericaceous plants. These groups of fungi can have profound impact on community of plants in soil environment. Studies conducted on Hymenoscyphus ericae revealed that H. ericae can produce extracellular enzymes such as phosphatases, proteases, cellulases and pectinases, which support the utilization of nitrogen, phosphorus and permitting access to other valuable nutrient embedded within the soil and decaying plant tissues. Most studies conducted on extracellular enzymes from these fungi majorly focused on the use of plating method to determine activity. Currently, there is little information on extracellular enzymes from ERM for the bio-economy, but there are proofs that some ericoid, ectomycorrhizal and dark septate endophytic fungi have the potential to produce a good number of hydrolytic enzymes in vitro. Therefore, this review seeks to employ available information on these fungi and their ability to produce enzymes when growing in liquid medium where their production can be optimized for commercial purposes.

Effect of crop rotation on the incidence of soil-borne fungal wheat pathogens

Nine varieties of soft spring wheat (Altayskaya 70, Altayskaya 75, Krasnoyarskaya 12, Novosibirskaya 15, Novosibirskaya 16, Novosibirskaya 29, Novosibirskaya 31, Novosibirskaya 41 and Svirel) were studied in the field experiment using fallow as a predecessor and wheat as a predecessor both with and without nitrogen fertilizer for an incidence of root infection caused by Fusarium spp., Alternaria spp. and Bipolaris sorokiniana. Average by varieties and variants of experiment incidence of Fusarium spp., Alternaria spp. and B. sorokiniana was 7.5, 5.7 and 10.8%, respectively. Wheat as a predecessor statistically significantly increased average by varieties incidence of both Fusarium spp. and Alternaria spp. in comparison with fallow. Nitrogen fertilizer statistically significantly increased average incidence of Fusarium spp., Alternaria spp. and B. sorokiniana. The incidence of fungal root infection and the effects of predecessor and fertilization statistically significantly depended on the variety.