Head: Mgr. Martina Janoušková, PhD.

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We study mutualistic mycorrhizal associations between specific soil fungi and plant roots, namely arbuscular mycorrhiza, ectomycorrhiza and ericoid mycorrhiza. We also focus on interactions between various types of mycorrhiza and their interactions with soil saprophytic fungi. Find out more at https://www.ibot.cas.cz/mykosym/.

 

Research topics

• Diversity, biogeography and community ecology of root-associated fungi
• Relationship between the composition and symbiotic functioning of mycorrhizal fungal communities
• Functioning of arbuscular mycorrhiza under drought
• Fungal symbioses of seagrasses
• Microbial inoculants in the development of specific cultivation methodologies

 

Selected recent results

1/ Benefits in plant N uptake via the mycorrhizal pathway in ample soil moisture persist under severe drought

Pot-grown tomato (Solanum lycopersicum, cv. ‘Micro Tom’) plants, either mycorrhizal (M; inoculated with Rhizophagus irregularis) or non-mycorrhizal (NM), were cultivated under precisely controlled substrate moisture to establish a gradient ranging from ample moisture to the wilting point. Isotopically labeled nitrogen (N) source – either inorganic (15NH4Cl) or organic (15N-labeled clover biomass) – was provided into mesh bags that excluded growth of roots, but were penetrable by mycorrhizal hyphae radiating from roots of M plants. This setup enabled to quantify the immediate N uptake under specific moisture and distinguish it from the long-term cumulative uptake. We found that M plants acquired strikingly more 15N derived from either the inorganic or organic source than their NM counterparts. The advantage of M plants in 15N uptake was manifested across the entire moisture range, although a declining trend was observed toward the drought extreme. Our study presents strong evidence that mycorrhiza can provide their host plants with significant advantage in N acquisition from root inaccessible zones across a wide range of substrate moistures.

• Püschel D., Bitterlich M., Rydlová J., Bukovská P., Sudová R. & Jansa J. 2023: Benefits in plant N uptake via the mycorrhizal pathway in ample soil moisture persist under severe drought. Soil Biology & Biochemistry 187, 1 – 11. https://doi.org/10.1016/j.soilbio.2023.109220

 
Greenhouse pot experiment studying mycorrhizal pathway of nitrogen acquisition by plants on a gradient of soil moisture. Lids cover tubes for moisture measurement without direct contact of probe with the soil, the nylon meshes indicate the position of meshbags with inorganic or organic ¹⁵N sources.

 

2/ Transferred communities of arbuscular mycorrhizal fungal persist in novel climates and soils

The study investigates the stability and adaptability of arbuscular mycorrhizal fungal (AMF) communities when transferred to new soil and climatic conditions on an elevation gradient in northern Arizona. Using two ecotypes of the common native grass Bouteloua gracilis, we assessed the impact of initial inoculum, soil, and climate on AMF community composition, diversity, and root colonization ability. Results show that AMF community composition is primarily influenced by the initial inoculum, with soil and climate changes having much smaller effects. Root colonization levels were significantly affected by soil and climate, but not by community origin. The study thus reveals that AMF communities are resilient, maintaining composition and adapting root colonization in new environments, and provides insights into mycorrhizal responses to environmental changes.

• Janoušková M., Remke M., Johnson N. C., Blažková A., Rydlová J., Kolaříková Z. & Bowker M. A. 2023: Transferred communities of arbuscular mycorrhizal fungal persist in novel climates and soils. Soil Biology & Biochemistry 187, 1 – 13. doi:1016/j.soilbio.2023.109190

One of the experimental localities in northern Arizona, where the transplantation experiment with Bouteloua gracilis and soil microbial communities was conducted (Blue Chute locality of Southwest Experimental Garden Array).

 

4/ The fine‐tuning of mycorrhizal pathway in sorghum depends on both nitrogen−phosphorus availability and the identity of the fungal partner

We described fine‐scale differences between two common arbuscular mycorrhizal (AM) fungal species in nutrient supply to their host plant. Plant physiological parameters and expression patterns of its ammonium and phosphate transporters indicated that AM fungi can supply nutrients to the host plant in a generalist mode (with uniform efficiency across conditions) or in a specialist mode, tuned e.g. to low phosphorus availability. The study thus showed how seemingly similar AM fungi can act complementarily in fluctuating nutritional conditions.

• Boussageon R., Marro N., Janoušková M., Brulé D., Wipf D. & Courty P. E. 2022: The fine‐tuning of mycorrhizal pathway in sorghum depends on both nitrogen−phosphorus availability and the identity of the fungal partner. Plant Cell and Environment 45, 3354-3366. doi:0.1111/pce.14426

Schematic presentation of generalist and specialist arbuscular mycorrhizal fungi in nutrient supply to the host plant. The generalist (a) supplies both nutrients with similar efficiency across a gradient of nutritional conditions, while the specialist (b) efficiently supplies phosphorus but retains nitrogen at low availabilities.

 

5/ Metaanalysis of the effects of arbuscular mycorrhizal fungal species and taxonomic groups on plants

The analysis provides a comprehensive overview on the benefits of different AMF species and taxonomic groups to plants and useful insights for their management and use. AMF had stronger positive effects on phosphorus nutrition than on plant growth and nitrogen nutrition, the effects on the growth of plants facing biotic and abiotic stresses were similarly positive. Diversisporales were the most beneficial AM group to plants without stress and Gigasporales to plants facing biotic stress.

• Marro N., Grilli G., Soteras F., Caccia M., Longo S., Cofré N., Borda V., Burni M., Janoušková M. & Urcelay C. 2022: The effects of arbuscular mycorrhizal fungal species and taxonomic groups on stressed and unstressed plants: a global meta-analysis. New Phytologist 235, 320 – 332. doi:10.1111/nph.18102

Correlation of the effects of AM species on phosphorus uptake by the plant [P (effect sizes)] and the effects on growth [Biomass (effect sizes)].

 

6/ PacBio sequencing of Glomeromycota rDNA: a novel amplicon covering all widely used ribosomal DNA barcoding regions

We developed a PCR approach specific to arbuscular mycorrhizal fungi (AMF), where we amplified approx. 2.5 kb of the ribosomal DNA (rDNA); the PCR products were then sequenced on the PacBio platform. Using our new method, we described complex communities of these important symbiotic fungi in environmental root and soil samples and provided their robust phylogenetic assignment. We consolidated information about AMF taxon distributions coming from three widely used barcoding regions.

• Kolaříková Z., Slavíková R., Krüger C., Krüger M. & Kohout P. 2021: PacBio sequencing of Glomeromycota rDNA: a novel amplicon covering all widely used ribosomal barcoding regions and its applicability in taxonomy and ecology of arbuscular mycorrhizal fungi. New Phytologist 231, 490 – 499. doi:10.1111/nph.17372

The ribosome-encoding gene operon, with the target 2.5 kb fragment highlighted in green. Three regions (SSU, ITS and LSU) often used in arbuscular mycorrhizal fungal community studies are shown using their flanking primers. Locations of the regions and PCR primers are shown approximately to scale.

 

7/ Drought accentuates the role of mycorrhiza in phosphorus uptake.

In a greenhouse experiment Medicago truncatula plants – either grown with or without symbiosis with arbuscular mycorrhizal fungi – were exposed to a unique 15-step gradient of substrate moisture, ranging from plentitude of water to severe deficiency. The application of phosphorus isotopes to the substrate and tracing in plant biomass revealed that mycorrhizal fungi significantly increased the immediate uptake of phosphorus by the plants, particularly so in intermediate moisture or under drought.

• Püschel D., Bitterlich M., Rydlová J. & Jansa J. 2021: Drought accentuates the role of mycorrhiza in phosphorus uptake. Soil Biology & Biochemistry 157, 1 – 11. doi:10.1016/j.soilbio.2021.108243

Scheme of an experiment exploring the role of mycorrhizal symbiosis in plant phosphorus uptake on a gradient of substrate moisture.

 

8/ Relative abundance of arbuscular mycorrhizal fungal species in communities is functionally relevant

The identity and diversity of arbuscular mycorrhizal (AM) fungal symbionts strongly affect the functioning of mycorrhiza, but little is still known about the functional relevance of the individual taxa abundances within AM fungal communities. We demonstrated, in controlled experimental conditions with medic (Medicago truncatula), the importance of the abundances of certain AM fungal species for plant nutrient uptake and growth as well as carbon drain into the fungi.

• Blažková A., Jansa J., Püschel D., Vosátka M. & Janoušková M. 2021: Is mycorrhiza functioning influenced by the quantitative composition of the mycorrhizal fungal community? Soil Biology & Biochemistry 157, 1 – 10. doi:10.1016/j.soilbio.2021.108249

Experimentally grown medic.

 

9/ Alien ectomycorrhizal plants differ in their ability to interact with co-introduced and native ectomycorrhizal fungi in novel sites

Establishment of alien trees outside their native range can be constrained by the absence of suitable fungal partners. Our metastudy shows that alien conifers rely upon association with co-introduced fungi from their native range, while alien eucalypts often form novel associations with fungi native to the region of introduction. Successful establishment of distinct groups of exotic trees can vary depending on their ability to associate with local fungi.

• Vlk L., Tedersoo L., Antl T., Větrovský T., Abarenkov K., Pergl J., Albrechtová J., Vosátka M., Baldrian P., Pyšek P. & Kohout P. (2020). Alien ectomycorrhizal plants differ in their ability to interact with co-introduced and native ectomycorrhizal fungi in novel sites. The ISME Journal, 14(9), 2336–2346. doi: 10.1038/s41396-020-0692-5

Global distribution of analysed ectomycorrhizal (EM) fungal communities (pie charts) associated with (a) alien conifers and (b) alien eucalypts. Colors of the pie charts indicate share of the three strategies that alien EM plants adapted to establish in new areas: interaction with co-introduced EM fungi from their native range (red), association with EM fungi which naturally occur in both native as well as introduced regions of the host plant (green), and establishment of novel associations with native EM fungal species (yellow). Native distribution ranges of Pinaceae and eucalypts are highlighted by green colour.

 

10/ Early successional ectomycorrhizal fungi are more likely to naturalize outside their native range than other ectomycorrhizal fungi

Ectomycorrhizal (EM) fungi are the key symbionts of numerous species of woody plants around the globe. Some have been co-introduced to a number of ecosystems along with their plant hosts. In this metastudy we investigated EM fungal communities associated with alien trees worldwide to assess the numbers and ecology of introduced EM fungi worldwide. Overall, we provide evidence that early succesional EM fungal species are more likely to naturalize in new areas on global scale.

• Vlk L., Tedersoo L., Antl T., Větrovský T., Abarenkov K., Pergl J., Albrechtová J., Vosátka M., Baldrian P., Pyšek P. & Kohout P. (2020). Early successional ectomycorrhizal fungi are more likely to naturalize outside their native range than other ectomycorrhizal fungi. New Phytologist, 227(5), 1289-1293. doi: 10.1111/nph.16557

 

11/ Interactions of saprotrophic and root symbiotic fungi control the transformation of humic substances and phosphorus in Norway spruce needle litter

 Our results show that interactions of fungi from different ecological guilds (saprotrophic, mycorrhizal, endophytic) influence the flow of phosphorus in decaying plant litter and the transformation of the soil organic matter itself. Mineralization of plant litter promoted by saprobes was slowed down by mycorrhizal but not by endophytic fungi. The tested fungi did not affect the amount of produced humic substances but changed their chemical characteristics. Dark pigmented fungi increased the relative proportion of carboxylic moieties in the humic substances probably via the production and incorporation of melanins. Effect of fungal interactions on the  humification and phosphorus flow was not uniform over the tested species demonstrating importance of species identity in the transformation process. Fungal root endophytes can significantly contribute to litter transformation along with mycorrhizal and saprotrophic fungi.

• Mrnka L., Koukol O., Hrabal R., Novák F. (2020) Soil biology and biochemistry 149: 107919, doi: https://doi.org/10.1016/j.soilbio.2020.107919

 

12/ Taxonomic placement and description of Posidoniomyces atricolor gen. et sp. nov., the dominant root symbiont of the Mediterranean seagrass Posidonia oceanica

It is assumed that seagrasses do not form mycorrhizae or any other specific root-fungus symbioses. The dominant Mediterranean seagrass Posidonia oceanica is an exception – recently, our team discovered that its roots host a unique symbiosis formed by a hitherto undescribed pleosporalean fungus, resembling the ubiquitous terrestrial root symbiosis with the so-called Dark Septate Endophytes. Thus, the aims of the present study were 1/ to investigate the distribution of the symbiosis, 2/ to describe the total fungal diversity in P. oceanica roots and 3/ to place taxonomically and describe the dominant pleosporalean symbiont. The symbiosis was present at all 32 investigated localities across the NW Mediterranean. At the same time, the total root fungal diversity was very low and dominated by the pleosporalean fungus. A multigene phylogenetic analysis confirmed that the fungus represents a new monotypic genus in the recently established Aigialaceae family and it was described as Posidoniomyces atricolor. The fungus is not known from any other hosts or environments and represents the only biotrophic representative in the Aigialaceae.

• Vohník M., Borovec O., Kolaříková Z, Sudová R, Réblová M. (2019) Extensive sampling and high-throughput sequencing reveal Posidoniomyces atricolor gen. et sp. nov. (Aigialaceae, Pleosporales) as the dominant root mycobiont of the dominant Mediterranean seagrass Posidonia oceanica. MycoKeys 55: 59–86. doi: 10.3897/mycokeys.55.35682

Posidoniomyces atricolor – characteristic root colonization pattern in the seagrass Posidonia oceanica and morphology of its colonies during isolation on nutrient media. a. In vivo colonization on the root surface (arrows) and in the hypodermis (asterisks) of P. oceanica; b. Dark septate endophytic colonization on the root surface; c. Germinating microsclerotia stained with trypan blue (arrows); d. Compact colony developed from microsclerotia (arrow); e. Surface-sterilized root segments yielding P. atricolor compact colonies (black arrows), sometimes with substrate mycelium (white arrows); f. Compact colonial morphotype of P. atricolor; g. Mycelial colonial morphotype of P. atricolor; h. Mycelial morphotype developing from microsclerotia (arrows) in transversal section. Scale bars: a, b = 20 μm, c = 50 μm, d = 100 μm, f, h = 200 μm, g = 500 μm.

 

13/ Survival and long-term infectivity of arbuscular mycorrhizal fungi in peat-based substrates stored under different temperature regimes

The study tested long-term infectivity of arbuscular mycorrhizal fungi (AMF) when introduced to a peat-based horticultural substrate and stored in five different temperature regimes (constant temperatures of −20, 5 or 20 °C) and two outdoor regimes simulating actual practice (shade and direct sunlight). Eight AMF inocula were tested, including 5 monocultures applied as 4% (v) of the substrate or their mixture in 1%, 4% and 8% (v) doses. Their infectivity was monitored for 56 weeks at 8-week intervals. In general, infectivity significantly decreased with time, but in three regimes including periods of cold (5 °C, shade and sunlight), cold stratification probably broke spore dormancy and led to temporal stimul­ation of AMF infectivity. Two AMF were found most resistant among the tested AMF. Except for storage at 5 °C, where a wider AMF spectrum maintained sufficient long-term viability, infectivity became very low after one year. Temperature fluctuations in direct sunlight were less negative than expected, whereas infectivity decline was surprisingly strong also in mild storage conditions (20 °C). Higher inoculum dose lengthened AMF infectivity. We ascribe the general decline of infectivity to unfavourable properties inherent to peat.

• Püschel D., Kolaříková Z., Šmilauer P. & Rydlová J. (2019). Survival and long-term infectivity of arbuscular mycorrhizal fungi in peat-based substrates stored under different temperature regimes. Applied Soil Ecology 140: 98-107. doi: 10.1016/j.apsoil.2019.04.020

 

14/ Abiotic conditions determine the functioning of mycorrhizal symbiosis independently of the community composition of the fungal symbionts

The experimental study addressed the relationship between abiotic conditions, the composition of mycorrhizal fungal communities and the host plant’s benefit from mycorrhiza. While the abiotic conditions fundamentally influenced the plant benefit, the fungal community composition was determined by the fungal species’ traits. The functioning of mycorrhiza on the continuum between mutualism and parasitism had only a small and transient effect on the fungal community.

• Voříšková A., Jansa J., Püschel D., Vosátka M., Šmilauer P. & Janoušková M. (2019). Abiotic contexts consistently influence mycorrhiza functioning independently of the composition of synthetic arbuscular mycorrhizal fungal communities. Mycorrhiza 29: 127-139. doi: 10.1007/s00572-018-00878-8

Greenhouse experiment focusing on the relationship of abiotic conditions, the composition of mycorrhizal fungal communities and the functioning of mycorrhizal symbiosis.