Arbuscular Mycorrhizal Fungi Population Research Articles

Populasi dan Keanekaragaman Fungi Mikoriza Arbuskular pada Rizosfer Tanaman Lada (Piper nigrum L.) Monokultur dan Polikultur

Arbuscular mycorrhizal fungi (AMF) is a type of fungus that comes from the endomycorrhizal group, these fungi have the ability to form symbiosis with almost 90% of higher plant species. Population and diversity of AMF are influenced by biotic factors and abiotic factors. This research aims to determine the differences in population, diversity and dominant types of AMF in the rhizosphere of pepper planted in monoculture and pepper in polyculture. The soil samples were taking from monoculture and polyculture pepper plantations in Air Naningan District, Tanggamus Regency. The AMF population was tested using the One way Annova test. Culture trapping was done using a factorial treatment with the first factor being the origin of the soil sample (K) and the second actor being the type of host plant (T). Treatments design used was randomize design (CRD). The results showed that the AMF population in polyculture pepper plantation soil samples was higher than monoculture pepper, based on the Shannon-Wiener Diversity Index, AMF diversity in monoculture pepper and coffee intercropping pepper plantations was higher than in cocoa intercropping pepper plantations, and the type of AMF was dominant. from the results of trapping culture with monoculture pepper garden soil samples, namely spores of the species code S7, in samples of coffee intercropping pepper plantations the code S7 is dominant, while in cocoa intercropping pepper plantations it is dominated by code S6. Keywords: Arbuscular mycorrhizal fungi, diversity, population.

Spores of arbuscular mycorrhizal fungi host surprisingly diverse communities of endobacteria.

Arbuscular mycorrhizal fungi (AMF) are ubiquitous plant root symbionts, which can house two endobacteria: Ca. Moeniiplasma glomeromycotorum (CaMg) and Ca. Glomeribacter gigasporarum (CaGg). However, little is known about their distribution and population structure in natural AMF populations and whether AMF can harbour other endobacteria. We isolated AMF from two environments and conducted detailed analyses of endobacterial communities associated with surface-sterilised AMF spores. Consistent with the previous reports, we found that CaMg were extremely abundant (80%) and CaGg were extremely rare (2%) in both environments. Unexpectedly, we discovered an additional and previously unknown level of bacterial diversity within AMF spores, which extended beyond the known endosymbionts, with bacteria belonging to 10 other phyla detected across our spore data set. Detailed analysis revealed that: CaGg were not limited in distribution to the Gigasporaceaefamily of AMF, as previously thought; CaMg population structure was driven by AMF host genotype; and a significant inverse correlation existed between the diversity of CaMg and diversity of all other endobacteria. Based on these data, we generate novel testable hypotheses regarding the function of CaMg in AMF biology by proposing that they might act as conditional mutualists of AMF.

Arbuscular mycorrhizal fungi association and root rot disease in mungbean (<i>Vigna radiata</i>) growing areas of Haryana

The study was carried out during rainy (kharif) seasons of 2021 and 2022 at Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana to provide a comprehensive understanding of how the presence and activity of arbuscular mycorrhizal (AM) fungi may influence the development of root rot in mungbean (Vigna radiata L.) crops in different mungbean-growing areas of Haryana. Root colonization by AM fungi in Hisar, Bhiwani, Mahendragarh, and Charkhi Dadri districts of Haryana ranged from 16.45 to 24.07%, 7.71 to 16.73%, 7.02 to 21.43% and 7.59 to 22.28%, respectively. This variability underscores the diverse interactions between mungbean plants and AM fungi in these distinct geographical regions, reflecting the influence of environmental factors and local soil conditions on mycorrhizal associations. Sporocarp numbers in these districts ranged from 76.5 to 131.5, 37 to 102, 54 to 119.5 and 65.5 to 118 per 100 g of soil, respectively. These findings emphasize the dynamic nature of AM fungal populations and their potential impact on the overall soil health and plant-microbe interactions in mungbean cultivation. Similarly, root rot incidence in these districts varied from 6.59 to 11.62%, 7.48 to 11.29%, 7.05 to 11.43% and 5.88 to 11.76%, while root rot intensity ranged from 2.77 to 4.82%, 2.70 to 4.61%, 2.06 to 4.61% and 2.43 to 4.85% in Hisar, Bhiwani, Mahendragarh, and Charkhi Dadri districts, respectively. This variability in root rot incidence and intensity highlights the susceptibility of mungbean crops to this detrimental disease and emphasizes the importance of region-specific strategies for disease management.

The influence of a soil amendment on the abundance and interaction of arbuscular mycorrhizal fungi with arable soils and host winter wheat.

Arbuscular mycorrhizal (AM) fungi have been shown to be associated with an estimated 70 % of vascular terrestrial plants. Such relationships have been shown to be sensitive to soil disturbance, for example, tillage in the preparation of a seed bed. From the application of arable soil management, AM fungal populations have been shown to be negatively impacted in abundance and diversity, reducing plant growth and development. The present study aims to utilise two sources (multipurpose compost and a commercial inocula) of mycorrhizal fungi for the amendment of arable soils supporting Zulu winter wheat under controlled conditions and quantify plant growth responses. A total of nine fields across three participating farms were sampled, each farm practicing either conventional, reduced, or zero tillage soil management exclusively. Soil textures were assessed for each sampled soil. Via the employment of AM fungal symbiosis quantification methods, AM fungi were compared between soil amendments and their effects on crop growth and development. The present study was able to quantify a mean 6 cm increase to crop height (P<0.001), 10 cm reduction to root length corresponding with a 2.45-fold increase in AM fungal arbuscular structures (P<0.001), a 1.15-fold increase in soil glomalin concentration corresponding to a 1.26-fold increase in soil carbon, and a 1.32-fold increase in the relative abundance of molecular identified AM fungal sequences for compost amended soils compared to control samples. Mycorrhizal inocula, however, saw no change to crop height or root length, AM fungal arbuscules were reduced by 1.43-fold, soil glomalin was additionally reduced by 1.55-fold corresponding to a reduction in soil carbon by 1.31-fold, and a reduction to relative AM fungal species abundance by 1.26-fold. The present study can conclude the addition of compost as an arable soil amendment is more beneficial for the restoration of AM fungi beneficial to wheat production and soil carbon compared to the addition of a commercial mycorrhizal inocula.

ANALISIS KORELASI KARAKTERISTIK TANAH (P TERSEDIA, BAKTERI PELARUT FOSFAT, C ORGANIK, DAN KAPASITAS TUKAR KATION) TERHADAP PRODUKTIVITAS JAGUNG DI KECAMATAN CIBUGEL, KABUPATEN SUMEDANG

Maize is the main strategic food crop in Indonesia's food supply, but the productivity of maize in Indonesia is still low. Increasing the productivity of maize can be done by understanding information about the characteristics of the soil on maize planting areas. The research aimed to evaluate the relationship of soil biological and chemical characteristics (available P, phosphate solubilizing bacterial population, arbuscular mycorrhizal fungal population, organic C, and cation exchange capacity) on maize plant productivity. The research was carried out in Cibugel District, Sumedang Regency. The research used descriptive survey and comparative methods on 18 soil samples. The maize planting area was obtained based on analysis and overlapping of land units in the form of; slope, elevation, climate and shelled maize production area. Maize planting land is at an altitude of 500-1,000 meters above sea level and with a slope of 10-30%. The results of correlation analysis showed that organic C, cation exchange capacity, and phosphate solubilizing bacteria had a positive correlation with maize productivity, while available P and arbuscular mycorrhizal fungi had a negative correlation. organic C had the highest close relationship with a value of r = 0.43, while the other parameters have a weak relationship.

Arbuscular Mycorrhizae Fungi Diversity in the Root–Rhizosphere–Soil of Tetraena mongolica, Sarcozygium xanthoxylon, and Nitraria tangutorum Bobr in Western Ordos, China

Arbuscular mycorrhizal fungi (AMF) are considered to be an essential indicator of ecosystem biodiversity and can increase a plant’s ability to withstand arid conditions. Despite the obvious significance of AMF in the root and rhizosphere system, little is known about how the AMF variety varies between the soil and roots of endangered plants and how this varies depending on habitats in dry and semiarid regions. This study aimed to address this research gap by investigating the characteristics and diversity of AMF colonization in Zygophyllaceae. Using Illumina MiSeq high-throughput sequencing, indigenous AMF in the roots and rhizosphere soil of three endangered plants (Tetraena mongolica, Sarcozygium xanthoxylon, and Nitraria tangutorum Bobr) were investigated. The three threatened plants had different AMF populations in their root and rhizosphere soils, according to a hierarchical clustering analysis. AMF communities in rhizosphere soil were more sensitive to LDA than root AMF communities based on linear discriminant analysis effect size (LEfSe). Glomus, Septoglomus, and Rhizophagus were seen to function as dominant fungi as the soil and root AMF populations carried out their various tasks in the soil and roots as a cohesive collective. Distance-based redundancy analysis (db-RDA) showed that pH, total phosphorus, and accessible potassium were closely associated with AMF communities. The pH of the soil appears to be an important factor in determining AMF community stability. These findings can serve as a guide for the use of AM fungus in the rehabilitation of agricultural land in arid regions. In summary, our work contributed new knowledge for the scientific preservation of these endangered plant species and for the further investigation of the symbiotic link between AMF and endangered plant species.

Taxonomical and functional analysis of four arbuscular mycorrhizal fungi populations obtained from a Ricinus communis rhizospheric Cr(VI) polluted soil

In a global context of climate change and loss of biodiversity, phytoremediation appears as a viable strategy to recover polluted soil. Phytoremediation is defined as a strategy to recover polluted soils by means of plants and the associated microorganisms. Arbuscular mycorrhizal fungi (AMF) are one of the most widespread soil microorganisms, they live in symbiosis with 70% of terrestrial plants. In the symbiotic relation, the fungal partner incorporates carbohydrates and lipids facilitated by the plant and the plant incorporates minerals facilitated by the fungal partner. Then, the inclusion of AMF in phytoremediation strategies should become a priority, not only because the presence of AMF will help the plant to adapt to the polluted soil but also because it could enhance the incorporation of carbon to the soil. In addition, the actual context of global biodiversity loss prioritizes the study of local populations in order to promote the incorporation of the local biodiversity to soil management, that includes phytoremediation. In the present work we aimed to taxonomically characterise four AMF populations obtained from Ricinus communis rhizospheric Cr(VI) polluted soil. In addition, we aimed to study the symbiosis and the mineral uptake of some elements, including phosphorus and chromium, in R. communis plants associated with each AMF population and re-exposed to Cr(VI). We found that three AMF populations grouped near Rhizophagus and one near Paraglomus accessions and that the four AMF populations were tolerant to the re-exposure to 8 ppm Cr(VI) substrate concentration. Finally, from the mineral content analysis, our results strongly suggest that Paraglomus sp., a taxon which appeared earlier in the evolution of AMF, was the population that best adapted to the re-exposure of 8 ppm Cr(VI). Thus, we suggest that future phytoremediation studies should include taxa from this early diverged genus.

Effect of arbuscular mycorrhizal fungi inoculation on revegetation at Nukui Dam site, Japan

The establishment of the surviving arbuscular mycorrhizal (AM) fungi, Gigaspora margarita Becker &amp; Hall, inoculated in revegetation at the Nukui Dam was studied. The population of AM fungi and AM colonization of three plant species Japanese hill cherry (Prunus jamasakura Sieb. ex Koidz, yamazakura-inoculated plant), eulalia (Miscanthus sinensis Anderss, susuki), and mugwort (Artemisia vulgaris Pampan, yomogi) were investigated to compare inoculated and non-inoculated treatments. The AM colonisation was enhanced in inoculated plots although natural or accidental AM fungi were involved in non-inoculated plots and successfully colonised. Coverage of soil surface was more than 80% and even reached nearly 100% in summer regardless of the soil amendment type.The number of spores and the percentage of colonisation of investigated plant roots, as well as the density of typical AM structures such as arbuscules, auxiliary cells, vesicles, and coiling hyphae by AM fungi in inoculated plots were higher than those in non-inoculated ones. Some spores were Gigaspora andGlomus-inoculated species and were relatively rich in inoculated plots of Yamazakura. There was a significant increase in the number of AM spores in inoculated treatments at a 5% confidence level (ANOVA, p&lt;0.05) in Susuki and Yamazakura. Much more spores of Gigaspora sp.occurred in the rhizosphere soil of Yamazakura and Susuki plants in inoculated plots than in non-inoculated plots (2.33 and 3.73 times, respectively).The colonisation intensity and spore number in the rhizosphere were positively correlated. Therefore, inoculation at an early establishment should be important for the successive development of AM-plant symbiosis formation.

Linking soil health to human health: Arbuscular mycorrhizae play a key role in plant uptake of the antioxidant ergothioneine from soils

Societal Impact StatementEvidence has emerged that the antioxidant ergothioneine may be important in preventing many inflammatory diseases in humans. However, ergothioneine is not produced by humans or plants and is only made by fungi and some bacteria in soils. As such, humans get ergothioneine from eating fungi (mushrooms) or plants that take it up from the soil. In this study, we found that growing plants with beneficial fungi called arbuscular mycorrhizal fungi increased the amount of ergothioneine in plant tissues. This suggests that promoting agricultural practices that maintain healthy populations of beneficial soil fungi may improve the nutritional quality of crops.Summary The amino acid ergothioneine (ERGO) has recently gained attention as an antioxidant that benefits human health. ERGO is produced by fungi and mycobacteria in soils and is acquired only from diet. The mechanism by which ERGO is transferred from soil to plant is unknown. Recent work has shown that tillage reduces the amount of ERGO in crops. As tillage also reduces arbuscular mycorrhizal fungi (AMF) populations, we examined the relationship between AMF and plant ERGO uptake. We grew asparagus, black beans, wheat, and oats with a variety of single and mixed species AMF inocula and compared ERGO levels of these plants to plants that were uninoculated. Mycorrhizal inoculation enhanced ERGO content across all plants. There was a positive correlation between AMF colonization level and plant ERGO content. AMF appear to be important mediators of plant ERGO uptake. Future research is needed to identify the mechanism that leads to higher ERGO in plants colonized by AMF in order to promote farming practices that enhance AMF populations and increase crop ERGO concentration in field settings.

Managing Arbuscular Mycorrhizal Fungi in Arid Columbia Basin Vineyards of the Pacific Northwest United States

<h3>Abstract</h3> <h3>Background and goals</h3> Arbuscular mycorrhizal fungi (AMF) are root symbionts that help grapevines acquire nutrients from soil. Growers in many regions, including the Columbia River basin of Oregon and Washington, lack information needed to best manage AMF. Such lacking information includes understanding whether natural AMF populations are sufficient to ensure healthy colonization in new plantings, and what factors influence AMF in established plantings. <h3>Methods and key findings</h3> AMF colonization of grapevine fine roots was determined in 32 commercial vineyards and in a vineyard that was heavily infested by the northern root-knot nematode (NRKN, <i>Meloidogyne hapla</i>). Root colonization by AMF was as extensive in young vines (one- to two-years-old) as in older vines (&gt;15-years-old) examined in the survey, and was high throughout the season in the single vineyard trial. AMF colonization was greater overall in red wine grape cultivars than in white wine grape cultivars. AMF colonization correlated negatively with soil nitrate and leaf nitrogen (N) concentrations across vineyards, while arbuscules in roots correlated negatively with NRKN populations in soil. Both AMF and arbuscules in roots correlated negatively with NRKN populations per unit of fine root length at the beginning and end of the growing season in the heavily infested vineyard. <h3>Conclusions and significance</h3> Results suggest that AMF populations in soils of the Columbia River basin are ample to ensure high levels of grapevine root colonization, so inoculation is likely not needed when planting or replanting vineyards in the region. AMF colonization was reduced by high N and high populations of NRKN in soil.

Study of Arbuscular Mycorrhizal Fungi population in the rhizosphere of oil palm planted on 4 different soil types in Central Kalimantan Indonesia

Arbuscular mycorrhizal fungi (AMF) are naturally found in the soil. The population of this fungus is influenced by environmental factors such as soil type. Different soil types have different characteristics and will affect the AMF population in the soil. Therefore, this study was carried out to determine the AMF population in the soil based on the number of spores in the rhizosphere of oil palm planted in 4 different soil types, namely Dystrudepts, Paleudults, Haplohumods, and Haplosaprists. Soil samples were taken from each soil type at 4 sample points. At each sample point, soil samples were taken from 5 adjacent oil palm trees. Rhizosphere soil samples were taken at 4 points inside the oil palm circle at a depth of up to 15 cm and 4 points from the outside and then composited to represent 1 sample point for inside and outside the circle. Extraction of AMF spores from soil samples was carried out by the wet sieving method. The results showed that the average number of AMF spores per 50 g of rhizosphere soil from inside and outside the oil palm circle were 66,7 and 53,5 spores for Dystrudepts, 115,5 and 91,5 spores for Paleudults, 27 and 71,8 spores for Haplohumods, and 83,3 and 55 spores for Haplosaprists respectively. In Dystrudepts, Paleudults, and Haplosaprists soil types, the number of spores in the rhizosphere of oil palm inside the circle was higher than outside. On the other hand, for Haplohumods soil types, the number of spores inside the circle was lower than outside the circle.

The Importance of Mycorrhizal Fungi in the Development and Secondary Metabolite Production of Echinacea purpurea and Relatives (Asteraceae): Current Research Status and Perspectives

The cultivation of Echinacea purpurea for commerce and obtaining high-quality plant material on a large scale remain a challenge for growers. Another challenge for the following decades is to create sustainable agriculture that meets society’s needs, has no environmental impact, and reduces the use of fertilizers and pesticides. The aims of this overview were: (1) to present the importance of the chemical compounds reported in E. purpurea; (1) to synthesize results about cultivation of the E. purpurea with arbuscular mycorrhizal fungi (AMF) and associated microorganisms; (2) to exemplify similar research with plants from the Asteraceae family, due to the limited number of published Echinacea studies; (3) to collect recent findings about how the inoculation with AMF affects gene expressions in the host plants; (4) to propose perspective research directions in the cultivation of E. purpurea, in order to increase biomass and economic importance of secondary metabolite production in plants. The AMF inocula used in the Echinacea experiments was mainly Rhizophagus irregularis. The studies found in the selected period (2012–2022), reported the effects of 21 AMFs used as single inocula or as a mixture on growth and secondary metabolites of 17 plant taxa from the Asteraceae family. Secondary metabolite production and growth of the economic plants were affected by mutualistic, symbiotic or parasitic microorganisms via upregulation of the genes involved in hormonal synthesis, glandular hair formation, and in the mevalonate (MVA), methyl erythritol phosphate (MEP) and phenylpropanoid pathways. However, these studies have mostly been carried out under controlled conditions, in greenhouses or in vitro in sterile environments. Since the effect of AMF depends on the variety of field conditions, more research on the application of different AMF (single and in various combinations with bacteria) to plants growing in the field would be necessary. For the identification of the most effective synergistic combinations of AMF and related bacterial populations, transcriptomic and metabolomic investigations might also be useful.

Impact of the Cultivation System and Plant Cultivar on Arbuscular Mycorrhizal Fungi of Spelt (Triticum aestivum ssp. Spelta L.) in a Short-Term Monoculture.

Native communities of arbuscular mycorrhizal fungi (AMF) constitute a natural biofertilization, biocontrol, and bioprotection factor for most agricultural crops, including cereals. The present study investigated the native AMF population in cultivated spelt, i.e., a cereal that has not been analyzed in this respect to date. In particular, the aim of the study was to determine the number of spores and the degree of AMF root colonization in two spelt cultivars (Franckenkorn and Badengold) from a 3-year monoculture grown in two different cultivation systems: conventional tillage and no-tillage systems. The study showed considerable accumulation of AMF spores in the soil (on average 1325 in 100 g of air-dry soil), with a wide range of their numbers, and not a very high degree of endomycorrhizal colonization (on average from 3.0% to 31%). The intensity of AMF growth in the subsequent cultivation years gradually increased and depended on the cultivation system as well as the growth stage and cultivar of the spelt. It was found that both analyzed AMF growth indices in the no-tillage system were positively correlated with each other. Moreover, their values were higher in the no-tillage system than in the conventional system, with statistical significance only for the number of spores. This was mainly observed in the variant with the Franckenkorn cultivar. The effect of the growing season was evident in both cultivation systems and spelt cultivars. It was reflected by intensification of sporulation and mycorrhization of spelt roots by AMF in summer (maturation stage) compared with the spring period (flowering stage).

Exploration And Morphology Identification of Spores Asbuscular Mycorrhizal Fungi from Horticultural Plantation

Differences in location and rhizosphere cause differences in species diversity and population of Arbuscular Mycorrhizal Fungi (AMF). In addition, not all AMF have the same morphological and physiological characteristics, therefore it is very important to know their identity. This study aims to determine the presence and number of spores as well as to determine the morphological characteristics of AMF originating from the rhizosphere of several horticultural crops in the agricultural land of Payakumbuh State Agricultural Polytechnic. The method used in this research is descriptive exploratory method by means of purposive sampling for soil sampling. While the stages of this research include: taking and collecting data in the field, determining the point of location for soil sampling, taking soil samples, analyzing soil properties in the laboratory, isolating AMF spores and identifying AMF spores morphologically. The conclusions of this study are 1) The population of AMF spores in horticultural land is high. The highest spore population was found in soil samples of the root area of shallot plants (556 spores per 10 g of soil), while the lowest number of spores was in soil samples of eggplant root areas (271 spores per 10 g of soil), 2) AMF exploration in several horticultural crops in the agricultural land of the Payakumbuh State Agricultural Polytechnic, based on morphological identification (shape, color and size), the AMF found consisted of three genera, namely Glomus sp, Gigaspora sp, and Scutelospora sp.

Tembotrione combinations on enzyme activities and arbuscular mycorrhiza in maize planted soil

Tembotrione, a new generation low dose herbicide applied solely or in combination with atrazine or 2,4-D for controlling complex weed flora in maize field. Frequent use of herbicides at higher rate and in combinations might be a threat to soil biological health. Hence the effect of tembotrione applied at 120 and 240 g/ha and its combination with surfactant isoxadifen-ethyl, atrazine and or 2,4-D as tank mix on soil enzymes and arbuscular mycorrhiza fungi infection and sporulation was assessed in this study. The enzymes dehydrogenase and alkaline phosphatase and the arbuscular mycorrhizal fungi population and root colonization were hindered by tembotrione applied at higher dose and with surfactant and atrazine though significant weed control was achieved. Thus, the tembotrione with surfactant isoxadifen-ethyl should be applied at recommended rate to control weeds. Also, continuous monitoring is essential to avoid effect on non-target organisms and maintain soil biological health when applied with atrazine for broad spectrum weed control in irrigated maize.

Büyük ölçekli tarımsal uygulama için endofiz mikorrhizasının inokülum üretimi üzerinde substrat ve konak bitki olarak yer fıstığı atıklarının etkisi

A pot culture experiment was conducted to study the effect of soil amendment with different forms of groundnut waste on spore population and root infection of indigenous Arbuscular Mycorrhizal fungal species i.e. Glomus mosseae under polyhouse conditions. Two angiospermic plant species viz. sorghum and sesame were also examined for mycorrhization potential in the study. Observations were made for percent root colonization, spore density of AM fungi and the effectiveness of AM fungi on the shoot and root biomass of both host plants. The results indicated that AM fungal spore population and colonization levels were substantially enhanced by the application of compost groundnut waste as a substrate over dry groundnut waste. Among growth parameters, plant height, root length and plant biomass were recorded more in sorghum than Sesame. On the whole, mycorrhization was reported the highest with 75 g/pot concentration of waste. Also, Sorghum appeared to be a better host than sesame.

Native AMF Communities in an Italian Vineyard at Two Different Phenological Stages of Vitis vinifera.

Arbuscular mycorrhizal fungi (AMF) are beneficial soil microorganisms that can establish symbiotic associations with Vitis vinifera roots, resulting in positive effects on grapevine performance, both in terms of water use efficiency, nutrient uptake, and replant success. Grapevine is an important perennial crop cultivated worldwide, especially in Mediterranean countries. In Italy, Piedmont is one of the regions with the longest winemaking tradition. In the present study, we characterized the AMF communities of the soil associated or not with the roots of V. vinifera cv. Pinot Noir cultivated in a vineyard subjected to conventional management using 454 Roche sequencing technology. Samplings were performed at two plant phenological stages (flowering and early fruit development). The AMF community was dominated by members of the family Glomeraceae, with a prevalence of the genus Glomus and the species Rhizophagus intraradices and Rhizophagus irregularis. On the contrary, the genus Archaeospora was the only one belonging to the family Archaeosporaceae. Since different AMF communities occur in the two considered soils, independently from the plant phenological stage, a probable role of V. vinifera in determining the AMF populations associated to its roots has been highlighted.

Phosphate Suppression of Arbuscular Mycorrhizal Symbiosis Involves Gibberellic Acid Signaling.

Most land plants entertain a mutualistic symbiosis known as arbuscular mycorrhiza with fungi (Glomeromycota) that provide them with essential mineral nutrients, in particular phosphate (Pi), and protect them from biotic and abiotic stress. Arbuscular mycorrhizal (AM) symbiosis increases plant productivity and biodiversity and is therefore relevant for both natural plant communities and crop production. However, AM fungal populations suffer from intense farming practices in agricultural soils, in particular Pi fertilization. The dilemma between natural fertilization from AM symbiosis and chemical fertilization has raised major concern and emphasizes the need to better understand the mechanisms by which Pi suppresses AM symbiosis. Here, we test the hypothesis that Pi may interfere with AM symbiosis via the phytohormone gibberellic acid (GA) in the Solanaceous model systems Petunia hybrida and Nicotiana tabacum. Indeed, we find that GA is inhibitory to AM symbiosis and that Pi may cause GA levels to increase in mycorrhizal roots. Consistent with a role of endogenous GA as an inhibitor of AM development, GA-defective N. tabacum lines expressing a GA-metabolizing enzyme (GA methyltransferase—GAMT) are colonized more quickly by the AM fungus Rhizoglomus irregulare, and exogenous Pi is less effective in inhibiting AM colonization in these lines. Systematic gene expression analysis of GA-related genes reveals a complex picture, in which GA degradation by GA2 oxidase plays a prominent role. These findings reveal potential targets for crop breeding that could reduce Pi suppression of AM symbiosis, thereby reconciling the advantages of Pi fertilization with the diverse benefits of AM symbiosis.

Exploring arbuscular mycorrhizal symbiosis in wetland plants with a focus on human impacts

Presence and functional roles of arbuscular mycorrhizal (AM) fungi in wetland environment have gained a global importance in recent past. Wetlands build a low-oxygen atmosphere, forming a completely different ecological environment for AM fungi, known more to occur in terrestrial environment. Nevertheless, as many 101 of AM fungi species, belonging to 19 genera and 9 families have been observed in the rhizosphere of wetland plants. In order to obtain oxygen, AM fungi expand the aeration system of wetland plants, store oxygen through their own vesicles, or change the structure of AM to survive. Human activities negatively affect the wetland environment, thus, reducing the population of AM fungi, while certain AM fungi species still improved the survival and development of wetland plants. AM fungi regulate different physiological activities of wetland plants in response to waterlogging stress, including an enhancement of antioxidant defense system, increased proline accumulation, improved plant growth and root morphology, responses of nutrients and aquaporins, and suppression in ethanol accumulation. The current review briefly summarized different species of wetland plants forming AM structures, the population of AM fungi inhabiting the rhizosphere of wetland plant, AM fungi-colonization of wetland plants, and the effect of AM fungi on physiological functions of wetland plants to neutralize the negative impact of waterlogging in addition to outlook of researchable issues. This review also highlighted human impacts on AM fungi of wetland plants and the impact of AM fungi on wetland environments and wetland plants.

Arbuscular mycorrhizal colonization rate of an exotic plant, Galinsoga quadriradiata, in mountain ranges changes with altitude.

Arbuscular mycorrhizal fungi (AMF) are suggested to be important for invasions by many exotic plants. However, it is not yet known how associations between AMF and invasive plant populations change in mountains ranges and how changed associations affect further expansion of different populations in new habitats. We conducted a field survey to detect AMF colonization rate of the invasive Galinsoga quadriradiata along an elevational gradient ranging from 223 to 1947masl in the Qinling and Bashan Mountains, China. Additionally, a greenhouse experiment was conducted to compare plant growth performance among five elevational populations. In the field, total plant mass and seed production, as well as root AMF colonization rate, significantly decreased with elevation. When populations were grown in a novel soil environment in the greenhouse, the high-altitude populations achieved higher seed and total mass at lower AMF colonization rate than the low-altitude populations. Moreover, high AMF association was related to high intraspecific competition within low-altitude populations and limited seed production. Our results revealed that the associations between AMF and G. quadriradiata decrease with altitude in mountain ranges, and this may indicate that differentiation of association between AMF and elevational populations occurs during range expansion of G. quadriradiata. The results of the greenhouse experiment suggest that the high-altitude populations are more aggressive than the low-altitude populations in a non-stressful environment.