Levels Of Mycorrhizal Colonization Research Articles

The effect of herbicides on arbuscular mycorrhizal fungi associated with annual invasive Asteroideae weeds

Invasive plants Galinsoga parviflora and Erigeron canadensis are common in crops and adjacent territories. One of the factors contributing to their spread is the community of arbuscular mycorrhizal fungi associated with these species. The nature of the symbiotic relationship between the host plant and AMF is determined by their phylogenetic position and place of growth. The aim of this work was to determine the level of mycorrhizal colonization of E. canadensis и G. parviflora growing in arable fields and along them. For plants at the flowering stage, high rates of frequency and intensity of mycorrhization were revealed. It has been shown that the level of mycorrhizal colonization of E. canadensis and G. parviflora is significantly influenced by the range of herbicides applied. The application of 2.4 D slightly reduced the intensity of colonization, but significantly stimulated the formation of arbuscules in plant roots. In turn, metribuzin prevented the formation of mycorrhiza. AMF associated with these plants formed a separate clade. This group, in our opinion, is responsible for more effective symbiosis with invasive plants of the Asteroideae subfamily and requires further closer study.

Cadmium uptake and mycorrhization by cacao clones in agroforestry and monoculture systems of Peruvian Amazon

The production system influences the cadmium (Cd) content and mycorrhization in cocoa plantations. The objective of this study was to determine the effects of different production systems on Cd uptake and the presence of mycorrhizas in cacao clones in field conditions, in the Peruvian Amazon. Twelve subplots of 108 m2 were selected in representative cocoa cultivation systems under agroforestry (AF) and monoculture (MON), with the cocoa clones ICS and CCN. Significant differences and data distribution were evaluated using ANOVA, principal component analysis, and Tukey's tests. Mycorrhizal colonization was higher in the AF_ICS system (71.11%) while the length of the extraradical mycelium was higher in the AF_CCN system (17.23%). The highest Cd content in soils was found under the AF_CCN and AF_ICS systems, both with 0.39 mg kg-1. The Cd content in cacao roots, leaves, and beans were higher in the MON_CCN system with 1.87, 2.06, and 1.12 mg kg-1 respectively. Cocoa monocultures (with both clones) generally showed lower levels of mycorrhizal colonization than agroforestry systems, which in turn (also for both clones) presented higher Cd content in beans, even exceeding the limit established by the world health authorities.

Effects of arbuscular mycorrhizal fungi on plant growth and herbivore infestation depend on availability of soil water and nutrients.

Fitness of plants is affected by their symbiotic interactions with arbuscular mycorrhizal fungi (AMF), and such effects are highly dependent on the environmental context. In the current study, we inoculated the nursery shrub species Artemisia ordosica with AMF species Funneliformis mosseae under contrasting levels of soil water and nutrients (diammonium phosphate fertilization), to assess their effects on plant growth, physiology and natural infestation by herbivores. Overall, plant biomass was synergistically enhanced by increasing soil water and soil nutrient levels. However, plant height was surprisingly repressed by AMF inoculation, but only under low water conditions. Similarly, plant biomass was also reduced by AMF but only under low water and nutrient conditions. Furthermore, AMF significantly reduced leaf phosphorus levels, that were strongly enhanced under high nutrient conditions, but had only minor effects on leaf chlorophyll and proline levels. Under low water and nutrient conditions, specific root length was enhanced, but average root diameter was decreased by AMF inoculation. The negative effects of AMF on plant growth at low water and nutrient levels may indicate that under these conditions AMF inoculation does not strongly contribute to nutrient and water acquisition. On the contrary, the AMF might have suppressed the direct pathway of water and nutrient absorption by the plant roots themselves despite low levels of mycorrhizal colonization. AMF inoculation reduced the abundance of the foliar herbivore Chrysolina aeruginosa on plants that had been grown on the low nutrient soil, but not on high nutrient soil. Fertilization enhanced the abundance of this herbivore but only in plants that had received the high water treatment. The lower abundance of the herbivore on AMF plants could be related to their decreased leaf P content. In conclusion, our results indicate that AMF negatively affect the growth of Artemisia ordosica but makes them less attractive to a dominant herbivore. Our study highlights that plant responses to AMF depend not only on the environmental context, but that the direction of the responses can differ for different components of plant performance (growth vs. defense).

Arbuscular mycorrhizal fungi inoculation and phosphorus application improve growth, physiological traits, and grain yield of rice under alternate wetting and drying irrigation

Climate change and agricultural malpractices are exacerbating drought in many parts of the world causing a substantial agricultural production loss. The improvement of drought tolerance in rice is crucial for maintaining productivity and ensuring global food security. Alternate wetting and drying (AWD) irrigation along with plant-microbe interaction through arbuscular mycorrhizal fungi (AMF) is a potential approach for enhancing rice production through AMF-induced up-regulation of tolerance and resilience against drought stress. Therefore, the ameliorative role of AMF inoculation and phosphorus (P) application on growth, physiological traits, and grain yield of rice was evaluated under water stress imposed through AWD irrigation. A factorial experiment consisting of four fertilizer treatments where the P percentage varied along with the recommended dose of nitrogen (N) with or without AMF inoculation (P100 as the control, P100 + AMF, P75 + AMF, and P50 + AMF), three soil water potential levels (0, −15, and −30 kPa), and two cultivation methods (wet direct seeding and transplanting) was conducted in a polyhouse. The subscript values of 100, 75, and 50 under P represent 100%, 75%, and 50% of the recommended field application dose. Data were collected on selected growth parameters, physiological traits, levels of mycorrhizal colonization, yield and its components, and water productivity of rice. The results revealed that P100 + AMF inoculated plants had 11%, 14%, 74%, and 54% higher leaf greenness, leaf relative water content, net photosynthetic rate, and grain yield, respectively, for wet direct-seeded plants at reduced soil water potential (−30 kPa) compared with non-inoculated plants (P100). Free proline accumulation gradually enhanced with decreasing soil water potential, and it was maximized by 77% at −30 kPa compared with 0 kPa for P50 + AMF (for transplanted plants). Free proline accumulation was also higher with decreasing soil water potential in AMF-inoculated plants than non-inoculated plants regardless of cultivation methods. Leaf osmotic potential was reduced by −0.5 to −1.2 MPa at −30 kPa compared with 0 kPa under different fertilizer doses. However, AMF inoculation (P100 + AMF and P75 + AMF) improved leaf osmotic potential of plants under severe water stress (−30 kPa) maintained through AWD irrigation resulting in better osmotic adjustment than non-inoculated plants. AMF inoculation improved the response of most of the evaluated physiological traits of rice and enhanced grain yield with higher P availability (even with a 25% reduction in its recommended dose) in the rhizosphere under drought stress. Thus, it can be concluded that AMF inoculation coupled with judicious P management is a promising approach for improving physiological and biochemical traits, grain yield, and water productivity of rice under AWD irrigation regardless of cultivation methods.

Evidence for the evolution of native plant response to mycorrhizal fungi in post-agricultural grasslands.

Plant–microbe interactions play an important role in structuring plant communities. Arbuscular mycorrhizal fungi (AMF) are particularly important. Nonetheless, increasing anthropogenic disturbance will lead to novel plant–AMF interactions, altering longstanding co‐evolutionary trajectories between plants and their associated AMF. Although emerging work shows that plant–AMF response can evolve over relatively short time scales due to anthropogenic change, little work has evaluated how plant AMF response specificity may evolve due to novel plant–mycorrhizal interactions. Here, we examine changes in plant–AMF interactions in novel grassland systems by comparing the mycorrhizal response of plant populations from unplowed native prairies with populations from post‐agricultural grasslands to inoculation with both native prairie AMF and non‐native novel AMF. Across four plant species, we find support for evolution of differential responses to mycorrhizal inocula types, that is, mycorrhizal response specificity, consistent with expectations of local adaptation, with plants from native populations responding most to native AMF and plants from post‐agricultural populations responding most to non‐native AMF. We also find evidence of evolution of mycorrhizal response in two of the four plant species, as overall responsiveness to AMF changed from native to post‐agricultural populations. Finally, across all four plant species, roots from native prairie populations had lower levels of mycorrhizal colonization than those of post‐agricultural populations. Our results report on one of the first multispecies assessment of local adaptation to AMF. The consistency of the responses in our experiment among four species provides evidence that anthropogenic disturbance may have unintended impacts on native plant species' association with AMF, causing evolutionary change in the benefit native plant species gain from native symbioses.

Effect of soil bacteriomes on mycorrhizal colonization by Rhizophagus irregularis—interactive effects on maize (Zea mays L.) growth under salt stress

In this study, we investigated the interactive effects of the arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis and soil bacteriomes on maize growth under salt stress (100 mM NaCl) and also the effect of salt and bacteriomes on the mycorrhizal infection levels. We found that soil bacteriomes directly promoted the growth of maize and indirectly enhanced maize biomass by increasing mycorrhizal colonization levels, irrespective of salt stress. Although R. irregularis by itself had no maize growth-promoting effect even at a high mycorrhizal colonization level in roots, its benefits to maize were reflected in other aspects, evidenced by the significantly increased rate of arbuscule formation (a proxy for a functional plant-AMF nutritional exchange) under salinity. A negative correlation between arbuscule colonization and root biomass suggested R. irregularis expands the role of maize roots. Besides, the positive correlation between the overall AMF colonization level and shoot biomass supported the tenet of a positive contribution of R. irregularis to maize growth. Our findings suggest that soil bacteriomes interactively work with R. irregularis, modulating the growth of maize by affecting the colonization of AMF in roots.

Interactive effect of biocontrol agents in the management of Fusarium rot in cardamom and its impact on plant defense mechanism

Cardamom plantations are subjected to constant threat due to the Fusarium rot disease caused by Fusarium oxysporum Schlecht which is pronounced during summer months. The current study deals with the identification of an effective and ecofriendly management practice for the disease through the use of biocontrol agents. Survey conducted between February and May 2019 revealed maximum disease severity and incidence in Pampadumpara panchayat of Nedumkandam block (84.40% and 100%) and minimum in Erattaar panchayat of Kattappanablock (50.40% and 60.00%). A pot culture experiment was conducted to study the effect of three bioagents (Glomus fasciculatum, Trichoderma asperellum and Pseudomonas fluorescens) individually as well as in combinations. Root inoculation of G. fasciculatum with basal application and spray with P. fluorescens as well as root inoculation of G. fasciculatum along with basal application of T. asperellum and P. fluorescens spray were identifiedto be effective against the disease. Disease suppression by the above bioagents was facilitated by reduced pathogen antagonist ratio in the soil, high level of mycorrhizal colonization in the roots and enhanced biochemical activity of defense enzymes like peroxidase, poly phenol oxidase and phenylalanine ammonia lyase in the plants.

Diversity of arbuscular mycorrhizal fungi (Glomeromycota) in adjacent areas of different land use in Nepal

Disturbances can affect the incidence of Arbuscular Mycorrhizal Fungi (AMF) in both agricultural and natural ecosystems. The present study is a first attempt for the qualitative assessment of AMF diversity in adjacent areas of a forest ecosystem with different land uses and assess levels of mycorrhizal colonization by these fungi. A total of five soil samples were taken randomly from each of the following areas situated within the same landscape: undisturbed coniferous forest (UF), degraded forest (DF) and cultivated land (CL). A total of 22 taxa of arbuscular mycorrhizal fungi belonging to eight genera were identified morphologically, Glomus and Acaulospora being the most common. Species richness ranged from 11-14 among land use areas, with 14 species in UF and 11 species in CL. Acaulospora mellea, Gigaspora sp. and two non-identified Glomus species were detected in all areas. While species richness did not differ significantly amongst areas, diversity at the family level was 43% less in CL than in UF. Mean mycorrhizal colonization was higher in DF (28%) than CL (20%). We concluded that land use mainly affected fungal diversity only at the family level and had no impact on mycorrhizal development in sampled roots. This work provides the first step to identify native AMF species in Nepal that might be cultured for further use by small farmers in a sustainable agriculture approach.

The individual and interactive role of arbuscular mycorrhizal fungi and Trichoderma viride on growth, protein content, amino acids fractionation, and phosphatases enzyme activities of onion plants amended with fish waste

The Green Revolution faced a great cost to meet ever-increasing demands for food, where indiscriminate use of agrochemicals resulted in non-friendly habitats. Therefore, the development of a sustainable approach to better crop production of onion seeds (Allium cepa L.) is very crucial. It is time to use organic waste as a replacement for agrochemicals by using arbuscular mycorrhizal fungi (AMF) and Trichoderma. Fish waste as representative of food waste acts as a leading cause of contamination of the environment. The interaction of AMF and Trichoderma viride on biomass, total soluble protein, mycorrhizal colonization, amino acids, phosphatases and phosphorus and nitrogen contents of onion plants grown in fish waste amended soil was studied. Fish waste has caused a slight increase in onions biomass, total free amino acids, and soluble protein content while with AMF and T. viride dual inoculation more increments were recorded; such increases were related to an increase in mycorrhizal colonization. T. viride application significantly increased the mycorrhizal colonization levels, but these were significantly reduced with waste addition. Analysis of amino acids in plants showed that their concentrations had changed as a result of waste addition combined with AMF and/or T. viride. The effectiveness of fish waste combined with low cost and health/environmental safety leads to a prediction that the introduction of fish waste coupled with fungi will become a more popular feature of agriculture in the future.

Soil biological response to multi-species cover crops in the Northern Great Plains

Farmers in semi-arid regions are experimenting with cover crop mixtures as partial summer fallow replacement, with the goal of increasing soil biological activity. We compared extracellular enzyme activity, microbial biomass, potentially mineralizable nitrogen (PMN) and mycorrhizal colonization levels after growing cover crops comprised of one or four functional groups. We asked whether cover crops can alter those soil processes and components relative to fallow during the cash crop growing season, and whether a cover crop mixture (CCM) will have a greater impact than a single-species legume green manure (LGM) after one and two rotations with wheat. Cover crops were planted at two sites in Montana April 2012 and May 2014, and at two additional sites in May 2013, and April 2015, terminated at each site approximately 60 days after seeding. Wheat was the cash crop for the following growing season. Cover crop treatments included a fallow control, a sole pea LGM, and a FULL mix consisting of eight species, with two species of each of four functional groups. Four additional treatments of single functional groups were compared following the second rotation of cover crops. The geometric mean of soil enzyme activity increased after cover crops relative to fallow (1.1–1.3 fold) at two sites after the first rotation, and by 1.1–1.4 fold after the second rotation at three sites. At the fourth site, the geometric mean of the FULL mix was greater than LGM or fallow by 1.4 and 1.5 fold. The response of individual enzymes was less consistent. Microbial biomass and PMN increased after LGM and/or FULL at three of eight site-years, by 1.2–1.7 for microbial biomass and 1.6–2.1 for PMN. Mycorrhizal colonization of wheat increased in at least one cover crop treatment relative to fallow at four of six site-years, and decreased in cover crops relative to fallow at one site. There were no differences in soil biological traits measured among single-functional-group treatments. Soil biological parameters were correlated with cover crop biomass in 7 of 16 comparisons at two sites after one rotation. After two rotations, 5 of 8 soil parameters were correlated with cover crop biomass at one site, with no correlations for the remaining sites. Precipitation declined 30–50 % from the first rotations at those three sites. Positive effects of cover crops on soil biological parameters in semi-arid systems may be measurable only when environmental conditions do not limit growth.

Odgovor industrijske rajčice na primjenu arbuskularnih mikoriznih gljiva u uvjetima konvencionalne proizvodnje

The potential effect of pre-inoculation of processing tomato (Solanum lycopersicum L.) plants with arbuscular mycorrhizal fungi (AMF) on yield and fruit properties was investigated in conventional production. Tomato seeds were sown in seedling trays filled with a substrate non-inoculated (AMF-) or inoculated (AMF+) by selected mycorrhizal strains. Seedlings were transplanted in Terra rossa soil and grown in conditions with mineral fertilization and irrigation. Tomato fruits were sampled at harvest. Tomato plants under both treatments had high levels of mycorrhizal colonization, due to applied inoculum (AMF+) or indigenous (AMF-) inoculum present in the soil. Applied AMF+ treatment increased P and decreased K content in tomato fruits. Content of trace elements such as As and V significantly increased, while Pb content significantly decreased in the fruits of AMF+ when compared to the AMF- treatment. No significant effect of AMF+ treatment was observed on yield, fruit quality (soluble solids, pH, total acidity, fruit firmness), lycopene and antioxidant activity of tomato fruits. The overall results suggest that processing tomato is highly susceptible to the indigenous AMF, while seedlings inoculation with selected AMF improves only total phenolic and P fruit content. This means that AMF have a potential application in commercial processing tomato production, however a targeted adaptation of management decissions is required for more extensive results.

Ectomycorrhizae determine chestnut seedling growth and drought response

Although agriculture focuses on row crops in the Midwestern US, chestnut (Castanea) would be a possible multipurpose agroforestry crop in erodible locations within this region. As ectomycorrhizal (ECM) colonization is often crucial for tree establishment and production, we addressed the importance of ECM colonization on chestnut performance by assessing: (1) natural ECM colonization in an established chestnut orchard, and (2) the effect of ECM inoculation on seedling establishment and drought response in a greenhouse. We selected 50 Chinese American hybrid chestnuts trees in a commercial orchard and assessed their level of mycorrhizal colonization in relation to distance from an adjacent forest, the source of inoculum. In the green house, we grew 80 seedlings from this orchard with and without mycorrhizal inoculation. Half were harvested to assess inoculation success and biomass; the remainder were subjected to experimental water stress which was evaluated with chlorophyll fluorescence using Fv/Fm values. In the orchard planted with uninoculated plants, ECM colonization decreased with distance from adjacent oak forest (P = 0.015), the putative ECM source, with an average of 29% root tips colonized. ECM inoculation increased seedling aboveground biomass by 16.4% in the greenhouse and generated 1.14 times more, but smaller stomata on leaves. Water stress in ECM inoculated seedlings also recovered faster from an experimental drought having significantly higher Fv/Fm value (P = 0.004) than uninoculated seedlings. Our study clearly indicates that ectomycorrhizal colonization can help chestnut trees in their early growth and stress tolerance and should be included into field plantings to minimize dependence on agricultural amendments.

The Integration of Bio and Organic Fertilizers Improve Plant Growth, Grain Yield, Quality and Metabolism of Hybrid Maize (Zea mays L.)

Expanding eco-friendly approaches to improve plant growth and crop productivity is of great important for sustainable agriculture. Therefore, a field experiment was carried out at the Faculty of Agriculture Farm, Mansoura University, Egypt during the 2018 and 2019 growing seasons to study the effects of different bio- and organic fertilizers and their combination on hybrid maize growth, yield, and grain quality. Seeds were treated with Azotobacter chrocoocum, arbuscular mycorrhizal fungi (AMF), Bacillus circulans, biogas slurry, humic acid (HA), and their combination aiming to increase the growth and yield of maize and to reduce the need for chemical fertilizers. The results showed that combined application of the biofertilizer mixture (Azotobacter chrocoocum, AMF, and Bacillus circulans) with organic fertilizers enhanced maize growth, yield, and nutrient uptake. Moreover, the bio-organic fertilization has improved the soluble sugars, starch, carbohydrates, protein, and amino acid contents in maize seeds. Additionally, the bio-organic fertilization caused an obvious increase in the microbial activity by enhancing acid phosphatase and dehydrogenase enzymes, bacterial count, and mycorrhizal colonization levels in maize rhizosphere as compared with the chemical fertilization. Additionally, the bio-organic fertilizers has improved α-amylase and gibberellins (GA) activities and their transcript levels, as well as decreased the abscisic acid (ABA) level in the seeds as compared to the chemical fertilizers. The obtained results of bio-organic fertilization on the growth parameters and yield of maize recommend their use as an alternative tool to reduce chemical fertilizers.

Neighborhood effects on soil properties, mycorrhizal attributes, tree growth, and nutrient status in afforested zones

A harmonious interspecies relationship is the key to the success of mixed afforestation. This study was conducted to assess the responses of afforestation species to their neighboring trees. We examined five types of stands—monocultures of Chinese pine (Pinus tabuliformis), black locust (Robinia pseudoacacia), sea‐buckthorn (Hippophae rhamnoides), and two mixtures (Chinese pine × black locust mixture and Chinese pine × sea‐buckthorn mixture)—in the Loess Plateau, northwestern China. The height and diameter at breast height of each tree species were measured, and rhizosphere soil, shoot, and root were sampled. In monocultures, black locust was taller than Chinese pine and sea‐buckthorn, while the height of Chinese pine and sea‐buckthorn was similar. In mixtures, Chinese pine grew better with sea‐buckthorn than alone as a result of modified soil properties and plant nutrition, but not with black locust. When Chinese pine was used as neighbors, it affected the level of arbuscular mycorrhizal (AM) colonization of black locust, soil properties and AM fungal spore density of black locust and sea‐buckthorn, but did not significantly affect their growth. Our results suggest that the reciprocal effects between tree species in mixture are not symmetric, and thus planning for efficient mixed afforestation requires knowledge of species‐specific growth rate, nutrient requirements, and species interactions.

Assessment of Local and Systemic Changes in Plant Gene Expression and Aphid Responses during Potato Interactions with Arbuscular Mycorrhizal Fungi and Potato Aphids.

This research examined aphid and plant responses to distinct levels (none, low, and high) of arbuscular mycorrhizal (AM) fungal root colonization by studying the association between potato aphids (Macrosiphum euphorbiae), potatoes (Solanum tuberosum), and AM fungi (Rhizophagus intraradices). It extends knowledge on gene expression changes, assessed by RT–qPCR, of ten defense-related genes at two time-points post-herbivory (24 h and 10 days), focusing on aphid-infested local leaves, non-infested systemic leaves, and roots. The results showed that aphid fitness was not altered by AM symbiosis. At 24 h, ETHYLENE RECEPTOR 1 gene expression was repressed in roots of aphid-infested non-mycorrhizal plants and aphid-infested plants with a high level of AM fungal root colonization, but not on aphid-infested plants with a low level of AM fungal root colonization. At 10 days, ALLENE OXIDE CYCLASE and POTATO TYPE I PROTEASE INHIBITOR were upregulated exclusively in local leaves of aphid-infested plants with a low level of AM fungal root colonization. In addition, local and systemic changes in plant gene expression appeared to be regulated exclusively by AM status and aphid herbivory. In summary, the gene expression data provide insights on mycorrhizal potato responses to aphid herbivory and serve as a starting point for future studies using this system.

Granular Bioactive Formulation of Trichoderma viride and Arbuscular Mycorrhizal Fungi for Biological Control of Cumin Wilt Disease

Cumin wilt caused by Fusarium oxysporum f. sp. cumini is the most destructive abundant disease, limiting the cumin production in Egypt. The objective of this study was to evaluate the efficacy of granular bioactive formulation of Trichoderma viride (GBTV) and arbuscular mycorrhizal fungi (AM) for biological control of cumin wilt disease. Ten Trichoderma species were isolated from the rhizosphere of healthy cumin plants and tested in dual culture assay against the growth of F. oxysporum. Trichoderma viride TC40, T. hamatum and T. koningii recorded the highest reduction in the growth of the target pathogen. Under greenhouse conditions, use of AM+GBTV formulation minimized F. oxysporum incidence and increased plant survival percentages. GBTV treatment alone came the second when compared to infected control. The greatest proportional increases in cumin plant growth were elicited by GBTV formulation and/or AM treatments. The highest level of mycorrhizal root colonization was noticed in the presence or absence of thepathogen. The biochemical parameters of the infected plants with AM or by GBTV treatment showed a pronounced increase in the plant content of total phenols, peroxidase and polyphenoloxidase activities. Under field conditions, AM+GBTV treatment highly reduced disease incidence of wilt symptoms and increased plant survival as equal as chemical fungicide. It also improved plant growth parameters and yield. The suggested formula is highly recommended for Fusarium wilt management and yield production of cumin plants.

Arbuscular mycorrhizal colonization of selected herbaceous plants under arid protected area in Tunisia

ABSTRACT Arbuscular mycorrhizal fungi (AMF) play an important role in plants growth and soils dynamic in all most ecosystems. The main objective of the present study was to evaluate the plant-AMF interactions on soil functions under arid protected area ‘Zarat-Gabès’ in Tunisia. AMF colonization was evaluated by visual observation of AMF in fine roots of eight herbaceous plants. The level of mycorrhizal colonization varied between plants. Astragalus corrugatus and Hippocrepis areolata showed the highest mycorrhizal performance. The relative spore number was significantly different across rhizosphere soils. Statistical analysis showed a clearly positive correlation between the number of spores and plant-mycorrhizal intensity. For microbiological parameters, our results showed that mycorrhizal plants improved significantly the various microbiological parameters. Rhizosphere soils of Astragalus corrugatus and Hippocrepis areolata presented the necessary microbial densities and microorganisms more stable compared to unplanted soil. This study allowed obtaining a new result that challenges us about the need for efficient management of natural resources in the objective of nature conservation.

Comparison of root colonization by arbuscular mycorrhizal fungi in energy crop species cultivated on arable land contaminated with heavy metals

Arbuscular mycorrhiza is a widespread terrestrial symbiosis, involving 80 – 85% of vascular plants in almost all ecosystems. AM fungi increase plant tolerance to heavy metals by developing mechanisms allowing immobilization metals within or near the root and preventing their translocation to the shoot. Therefore, AMF could be involved in phytostabilization of heavy metals contaminated soils. The aim of the presented study was to explore the effect of heavy metals on arbuscular mycorrhizal fungi (AMF) root colonization of selected energy crop species: Miscanthus x giganteus, Panicum virgatum and Spartina pectinata cultivated on heavy metals contaminated arable land under different fertilisation (NPK vs. microbial inoculation). All examined plant species formed arbuscular mycorrhizal associations and differences in degree of mycorrhizal colonization among experimental variants were found. Influence of soil fertilization on AMF root colonization wasspecies-dependent. Both NPK fertilization and microbial inoculation resulted in reduction of mycorrhizal colonization in Miscanthus x giganteus, whereas in Panicum virgatum degree of AMF root colonisation was increased. Soil fertilisation had no effect on degree of Spartina pectinata root mycorrhization, sincethey were almost fully colonized independly on fertilization. In conclusions, contamination with heavy metals did not result in restriction of mycorrhizal colonization, which could be a consequence of AMF adaptation to such conditions. Nevertheless, among tested species, higher level of mycorrhizal colonization was found for Spartina pectinata roots. It indicates the highest susceptibility of this species to development of mycorrhizal structures regardless of heavy metal pollution and fertilization.

Root-associated fungi increase male fitness, while high simulated herbivory decreases indirect defenses in Croton lachnostachyus plants

Plants interact with a diverse array of organisms below and above ground; some interactions with ants allow plants to be protected against herbivorous insects, influencing their growth or reproduction. In addition, indirect plant defenses—such as those mediated by extrafloral nectaries (EFNs)—could be affected by plant root symbionts. However, it is not clear how the suppression of root symbionts might affect extrafloral nectar (EFN) production and plant reproductive output. We made an experimental study with a shrub species with EFNs. Firstly, we tested if root-associated fungi (i.e., comparing plants with and without fungicide) increased the production of pollen (male function) and EFN (volume, nectar concentration, and total sugar content) in Croton lachnostachyus. Subsequently, we implemented a second experiment on the same plants, adding different levels of simulated herbivory (none, low, high) to assess the combined effects of root-associated fungi and herbivory. While we found high levels of mycorrhizal colonization, we found no signs of pathogenic fungi and negligible values of dark septate endophytes in roots so we attributed our results mostly to arbuscular mycorrhizal fungi (AMF). The first experiment showed that plants without the fungicide treatment increased pollen production and secreted a lower mean volume of EFN with higher concentration of dissolved soluble solids. In the second experiment, high levels of simulated herbivory showed a diminution on EFN variables; also, we detected a lower shoot dry mass on plants with low levels of herbivory and no interactions with AMF. Our results suggest complex ecological responses related to the root-associated fungal community and simulated herbivory.

High levels of arbuscular mycorrhizal fungus colonization on Medicago truncatula reduces plant suitability as a host for pea aphids (Acyrthosiphon pisum).

This study sheds light on a poorly understood area in insect–plant–microbe interactions, focusing on aphid probing and feeding behavior on plants with varying levels of arbuscular mycorrhizal (AM) fungus root colonization. It investigates a commonly occurring interaction of three species: pea aphid Acyrthosiphon pisum, barrel medic Medicago truncatula, and the AM fungus Rhizophagus irregularis, examining whether aphid‐feeding behavior changes when insects feed on plants at different levels of AM fungus colonization (42% and 84% root length colonized). Aphid probing and feeding behavior was monitored throughout 8 h of recording using the electrical penetration graph (EPG) technique, also, foliar nutrient content and plant growth were measured. Summarizing, aphids took longer to reach their 1st sustained phloem ingestion on the 84% AM plants than on the 42% AM plants or on controls. Less aphids showed phloem ingestion on the 84% AM plants relative to the 42% AM plants. Shoots of the 84% AM plants had higher percent carbon (43.7%) relative to controls (40.5%), and the 84% AM plants had reduced percent nitrogen (5.3%) relative to the 42% AM plants (6%). In conclusion, EPG and foliar nutrient data support the hypothesis that modifications in plant anatomy (e.g., thicker leaves), and poor food quality (reduced nitrogen) in the 84% AM plants contribute to reduced aphid success in locating phloem and ultimately to differences in phloem sap ingestion. This work suggests that M. truncatula plants benefit from AM symbiosis not only because of increased nutrient uptake but also because of reduced susceptibility to aphids.