Arbuscular Mycorrhizal Fungi Spores Research Articles

Respuesta del pasto Yacaré (Urochloa híbrido cv. CIAT BR02/1752) a la biofertilización con hongos micorrízicos arbusculares

With the aim to evaluate the biofertilization effectiveness with arbuscular mycorrhizal fungi in Yacare pasture ( Urochloa hybrid) cultivated in Lixiviated Ferrallitic Red soil, an experiment was carried out at Nina Bonita Genetic Cattle Enterprise. Four treatments were evaluated: three species of arbuscular mycorrhizal fungi (AMF), Glomus cubense , Funneliformis mosseae , and Rizhophagus irregularis , in addition to a control without inoculating, distributed in a Latin square design. Different species inoculation of AMF was carried out at sowing time. The indicators evaluated were the frequency and intensity of mycorrhizal colonization, AMF spore number in the rhizosphere, the NPK biomass concentrations, the dry mass yield of the pasture and its nutritive value, as well as the efficiency index and AMF strains influence in pasture nutrition. All the strains produced significant increases in the evaluated variables; nevertheless, when G. cubense was inoculated, increases in the efficiency index and in pasture nutrition were obtained. It is concluded that biofertilization with G. cubense can be an effective agronomic practice to improve the yield and nutritive value of the Yacare pasture cultivated in Lixiviated Ferrallitic Red soil.

Soil environmental factors shape the rhizosphere arbuscular mycorrhizal fungal communities in South African indigenous legumes (Fabaceae)

Abstract. Alimi AA, Adeleke R, Moteetee A. 2021. Soil environmental factors shape the rhizosphere arbuscular mycorrhizal fungal communities in South African indigenous legumes (Fabaceae).Biodiversitas 22:2466-2476.The crucial role played by arbuscular mycorrhizalfungi (AMF) in the nutritional adaptation of plants tonutrient-deficientsoils is well recognized. However, little is known about the diversity of AM fungal communities in the rhizosphere of indigenous legumes of South Africa. This study presents the first morphological characterization of the AM fungal diversity present in the rhizosphere of eleven indigenous legume species fromtwo provinces in South Africa and correlates the diversity and community structure of AMF to soil physicochemical properties. Twenty AM fungal species belonging to ten genera were identified; Glomusand Acaulospora were the dominant genera, while Acaulospora colombiana, A. mellea, and Claroideoglomus etunicatumwere the prevalent species. The AM fungal spore density, diversity, andcommunity structurediffered markedly among the legume species in both provinces. Correlation and canonical correspondence analyses revealed that the diversity and spatial structure of AM fungal communitieswere significantly influenced by soil properties. This study providesa theoretical insight into the future potential of using the dominant AM fungal species as inoculants for sustainable management of legumes and indicated that soil factors are important environmental determinants of AM fungal diversity and community structure

Root Colonization and Spore Abundance of Arbuscular Mycorrhizal Fungi Along Altitudinal Gradients in Fragmented Church Natural Forest Remnants in Northern Ethiopia.

Arbuscular mycorrhizal fungi (AMF) spore density and root colonization are considered sensitive to host species and abiotic factors such as climate and soil. However, there is a knowledge gap about how fragmented native forest remnants might contribute to AMF conservation, what is the AMF spore density and root colonization, and to what extent climate change, particularly warming, might impact AMF. The aim of the study was to quantify the AMF spore density and root colonization along altitudinal gradients in three agro-ecological zones of nine church forests in northern Ethiopia. Data were collected from 45 plots. All the surveyed church forest species were colonized by AMF. However, we found a significant (p < 0.05) decrease in root colonization and AMF abundance in forests at high elevation. The topsoil had significantly (p < 0.05) higher root colonization and AMF abundance than subsurface soil. We found strong negative correlations between altitude and both spore density and root colonization and soil fertility. While we cannot separate whether spore density was temperature or soil limited, we can demonstrate the importance of conserving certain tree species, particularly Ficus species, which harbor high spore densities, in both lowland and midland church forests. In the highland, no Ficus species were found. However, Hagenia abyssinica, another Rosales, had the highest spore density in the highland ecoregion.

GRUPOS MICROBIANOS EN UN AGROECOSISTEMA MILPA INTERCALADA CON ÁRBOLES FRUTALES EN VALLES ALTOS DE PUEBLA, MÉXICO

&lt;p&gt;&lt;strong&gt;Background:&lt;/strong&gt; Microorganisms play a fundamental role in soil dynamics of agroecosystems. &lt;strong&gt;Objective:&lt;/strong&gt; To determine soil quality parameters and the abundance of functional groups of edaphic microorganisms in eight different contrasting sites evaluated in a milpa agroecosystem interclassed whit fruit trees (MIAF) and in monocultures system. &lt;strong&gt;Methodology:&lt;/strong&gt; Bulk density, humidity, pH, electrical conductivity, percentage of ash, oxidizable organic matter, oxidizable carbon, total nitrogen, inorganic nitrogen and nutrients (NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt;, Na&lt;sup&gt;+&lt;/sup&gt;, Ca&lt;sup&gt;2+&lt;/sup&gt; and K&lt;sup&gt;+&lt;/sup&gt;) were determined in composite soil samples by triplicate for each sites, as well as the diversity of weeds and abundance of total actinomycetes, nitrogen-fixing actinomycetes, yeasts, fungi, bacteria, and arbuscular mycorrhizal fungal spores. A principal component analysis was carried out to calculate a soil quality index (SQI). Analysis of variance, Tukey's mean comparison test (P ≤ 0.05), linear correlation, cluster analysis and canonical correlation were performed. &lt;strong&gt;Results:&lt;/strong&gt; A greater amount of total actinomycetes (&amp;gt; 4 Log CFU g&lt;sup&gt;-1&lt;/sup&gt; soil) and nitrogen-fixing actinomycetes (&amp;gt; 3.8 Log CFU g&lt;sup&gt;-1&lt;/sup&gt; soil) and fungi (&amp;gt; 1.7 Log CFU g&lt;sup&gt;-1&lt;/sup&gt; soil) were observed in the MIAF system compared to the monocultures. For the sites with corn-bean association in the MIAF system, a high positive correlation was observed between organic matter content and nitrogen-fixing actinomycetes (r = 0.60) and yeasts (r = 0.73), as well as with the percentage of total nitrogen with yeasts (r = 0.70) and nitrogen-fixing actinomycetes (r = 0.75). &lt;strong&gt;Implications:&lt;/strong&gt; The methodology used allowed the grouping of the sites studied, based on the SQI and a reduced set of variables. &lt;strong&gt;Conclusion:&lt;/strong&gt; The MIAF system favored the abundance of functional groups, soil quality parameters and the availability of nutrients in the soil compared to the monoculture sites.&lt;strong&gt; &lt;/strong&gt;&lt;/p&gt;

Propagation and characterization of viable arbuscular mycorrhizal fungal spores within maize plant (Zea mays L.).

The harmful effect of chemical fertilizer application on human health and the environment as a modern method of meeting the food demand of the increasing world population demands an urgent alternative that is environmentally friendly, which will pose no harm to human health and the environment. Arbuscular mycorrhizal fungi (AMF) are beneficial soil microorganisms that provide various ecological functions in increasing soil fertility and enhancing plant growth. This present study aimed to propagate, characterize and examine the effect of viable arbuscular mycorrhizal fungal spores on maize (Zea mays L) hosts using molecular methods. The propagation of AMF in the host plant using sterile soil and vermiculite was conducted in the greenhouse. The effect of AMF inoculation revealed a significant difference (P > 0.05) in maize growth, root colonization and AMF spore count when compared with the control. In all the parameters measured in this study, all the AMF spores propagated had a positive effect on the maize plant over the control, with the highest value mostly recorded in Rhizophagus irregularis AOB1. The molecular characterization of the spore using a specific universal primer for Glomeromycota established the success of the propagation process, which enhanced the classification of the AMF species into Rhizophagus irregularis OAB1, Glomus mosseae OAB2 and Paraglomus occultum OAB3. This finding will be a starting point in producing arbuscular mycorrhizal inoculum as a biofertilizer to enhance plant growth promotion. © 2021 Society of Chemical Industry.

Arbuscular mycorrhizal status of Erythrina brucei in different land use types in Ethiopia

Erythrina brucei is a leguminous tree commonly used in agro-forestry practices in southern and southwestern Ethiopia. It has desirable agro-forestry attributes that make it a good candidate for agro-forestry systems. However, there is a scarcity of information regarding species diversity and spore density of arbuscular mycorrhizal fungi (AMF) associated with E. brucei growing in different land use types. Therefore, this study was initiated to determine species diversity and richness in trap cultures of AMF associated with E. brucei growing in different geographic locations in various land use types of Ethiopia. Soil samples were collected from various E. brucei growing areas with different land use patterns. Trap culture was established using a portion of each soil sample by planting E. brucei as the host plant. AMF spore extraction was carried out in field and trap culture soils, and AMF species identification was done using spore morphology. Erythrina brucei root colonization with AMF structures was studied using trap culture, and AMF spore density in both field and trap culture soil samples was determined. A total of 11 AMF genera and 33 AMF species were recovered. The highest number of genera was recovered from forest land use type at Rebu Gebeya, followed by Adiskdam, live fence land use type. Glomus and Acaulospora were the dominant AMF genera covering 73% of the samples and contained 10 and 9 AMF species, respectively. All the soil samples contained indigenous AMF spore populations regardless of their origin and land use types. The highest mean AMF spore density in a field soil sample was recorded at a farmland in Bodite (280 spores 100 g−1 of dry soil), while the lowest was from Hossana (172 spores 100 g−1of dry soil). However, the highest mean AMF spore density in trap culture was detected from a farm land at Humbo (715 spores 100 g−1 of dry soil) and the lowest from Dhakallo (217 spores 100 g−1 of dry soil). Direct extraction of AMF from field soil samples showed lesser AMF spore density compared with trap culture in the same soil sample. All E. brucei root segments were colonized with the AMF structures, and the colonization status ranged from 34.4% to 49.1%. Both geographic location and land use type significantly affected AMF species richness (p < 0.05). Undisturbed land use types were characterized by high species richness. The soil pH and available phosphorus were negatively correlated to AMF spore density (p < 0.05), but AMF root colonization did not show any significant correlation. Moreover, significant correlations were also not observed between spore number and root colonization, and available phosphorus and root length colonization. We conclude that diverse and dominant AMF genera inhabited the rhizosphere of E. brucei, which can be used for the enhancement of host plant growth. To explore AMF species diversity and richness across geographic location and land use types in detail enhanced area coverage and the combination of both direct field soil and trap culture techniques are recommended.

Biocrusts inside and outside of Mimosa luisana resource islands as reservoirs of arbuscular mycorrhizal fungi in a Mexican semiarid ecosystem

Background: Arbuscular mycorrhizal fungi (AMF) and biocrusts (BC), occur inside and outside Mimosa luisana resource islands (M. luisana-RI) at the Tehuacán-Cuicatlán Valley, Puebla-Oaxaca, Mexico.&#x0D; Objectives: To determine: 1) Whether there are AMF within biocrusts, 2) The abundance and richness of AMF, and 3) The potential of AMF propagation in BC and soil below BC inside (BC-RI, soil-BC-RI) and outside (BC-ORI, soil-BC-ORI) M. luisana-RI, and open areas (OA), in the rainy (September 2011) and dry (May 2012) seasons.&#x0D; Methods: AMF were extracted of biocrusts and soil samples collected inside and outside M. luisana-RI and OA, in both seasons. Spore abundance and species richness, as well as potential propagation of AMF were determined in laboratory and greenhouse.&#x0D; Results and Conclusions: Biocrusts inside and outside M. luisana-RI form reservoirs of AMF spores and species richness (12 spp.), and act as “shields” protecting AMF compared with OA (5 spp.). Seasonal changes in the AMF composition within the biocrusts and the soil suggest that the availability of water drives AMF assemblages. The AM fungal spores in BC-RI and BC-ORI have a high potential of propagation; however, the BC-ORI by buffering the loss of AMF in soil-BC-ORI, they form mycorrhizal inocula within the soil.

Effect of single and mixed inoculation of arbuscular mycorrhizal fungi and phosphorus fertilizer application on corn growth in calcareous soil

Abstract. Ishaq L, Adu Tae ASJ, Airthur MA, Bako PO. 2021. Effect of single and mixed inoculation of arbuscular mycorrhizal fungi and phosphorus fertilizer application on corn growth in calcareous soil. Biodiversitas 22: 1920-1926. Low availability of soil phosphorus (P) in calcareous soil in West Timor has become a constraint in improving plant productivity. A field experiment was carried out in the calcareous soil to investigate the effect of single and mixed indigenous arbuscular mycorrhizal fungi (AMF) inoculation and P fertilizer application on growth and yield of corn in Kupang District, East Nusa Tenggara Timur Province, Indonesia. The experiment was laid out in a split-plot design consisting of indigenous AMF inoculation as the main plots and inorganic P fertilizer rates as the sub-plot treatments. The main plot treatments were: without AMF inoculation (M0), inoculated with single AMF inoculum (M1) and inoculated with mixed AMF inocula (M2). Sub-plots consisted of four P rates namely 25% (P1), 50% (P2), 75% (P3) and 100% (P4) of the recommended inorganic superphosphate dose of 200 kg SP36 ha-1. The results showed that there were significant interactions between AMF inoculation and P fertilizer dose on AMF spore density, AMF colonization and soil available P. Results indicated a strong correlation between AMF colonization and soil available P. Inoculation of both M1 and M2 significantly increased soil available P, plant growth and yield compared to the uninoculated plant. Spore production in the two AM responded differently to P fertilizer. Low doses of inorganic P fertilizer favored spore production in M1, whereas P fertilizer sporulation in M2 was adversely affected. The percentage of AMF root colonization of M1 and M2 decreased with an increase in P fertilizer applied. Further studies need to be conducted to evaluate the effectiveness of indigenous AMF in improving plant yield at low level of inorganic fertilizer application to achieve more sustainable agricultural practice in the region.

Combination of arbuscular mycorrhizal fungi and phosphate solubilizing bacteria on growth and production of Helianthus tuberosus under field condition

In this work, the effects of co-inoculation between an arbuscular mycorrhizal fungus (AMF) and a phosphate solubilizing bacteria (PSB) to promote the growth and production of sunchoke under field condition were investigated during 2016 and 2017. Four treatments were set up as follows: plants without inoculation, with AMF inoculation, with PSB inoculation and with co-inoculation of PSB and AMF. The results showed the presence of PSB and AMF colonization at the harvest stage in both years. This suggested the survival of PSB and successful AMF colonization throughout the experiments. According to correlation analysis, PSB positively affected AMF spore density and colonization rate. Also, both AMF and PSB positively correlated with growth and production of sunchoke. Co-inoculation could enhance various plant parameters. However, better results in 2016 were found in co-inoculation treatment, while AMF inoculation performed the best in 2017. All of these results suggested that our AMF and PSB could effectively promote growth and production of sunchoke under field conditions. Such effects were varied due to different environmental conditions each year. Note that this is the first study showing successful co-inoculation of AMF and PSB for promoting growth and yield of sunchoke in the real cultivation fields.

Effects of arbuscular mycorrhizal fungi on Solidago canadensis growth are independent of nitrogen form

Abstract Aims Invasive plants may alter soil fungal communities in a way that improves their growth. Nitrogen (N) content of soil affects the symbiosis between plants and arbuscular mycorrhizal fungi (AMF), further determining plant growth. Yet, it is unclear whether altered AMF communities change the dependence of invasive and native species on N-form, and whether N forms alter the invasive plant–AMF interaction (PSIM). Methods Two synthetic plant communities, including four Solidago canadensis individuals and four native plant species, were inoculated with AMF spores from S. canadensis-invaded soils and adjacent non-invaded soils, and were provided with nitrate, ammonia or glutamate. After their growth, the performance of the two plant communities in treatments of AMF origin and N forms, and the pathways of the N forms affecting S. canadensis growth and PSIM were evaluated. Important Findings Solidago canadensis had no obvious N-form dependence in any of the AMF inoculations. Native plant species showed weak N-form dependence, but invasive AMF could remove their N-form dependence. In the absence of N, AMF did not affect growth of S. canadensis and the native plants. In contrast, with N addition, invasive AMF significantly increased belowground and total biomass of the invasive plants but not those of the native plants. Positive PSIM of S. canadensis was also evidently greater than that of native plant species and was realized through directly or indirectly regulating phenotypic traits including plant height, leaf number and number of rhizomes. Our findings emphasize the importance of plant–AMF interactions and a unique N-acquisition strategy during plant invasions.

Interaction between mycorrhizal fungi and Meloidogyne javanica on the growth and essential oil composition of basil (Ocimum basilicum)

Plant-parasitic nematodes and arbuscular mycorrhizal fungi (AMF) have been reported to alter the yield and chemical composition of basil (Ocimum basilicum) essential oil. The aim of this study was to evaluate the effectiveness of AMF to control the root-knot nematode Meloidogyne javanica in basil and to investigate the effects of nematode-AMF interactions on plant growth, phosphorus (P) absorption, and essential oil composition. The experiment was conducted under greenhouse conditions following a completely randomized 3 × 2 factorial (two fungal species and an uninoculated control × inoculated and uninoculated seedlings) arrangement with 10 replicates. Substrates were inoculated with Claroideoglomus etunicatum, Rhizophagus clarus, or no fungi (control) and sown with basil seeds. After 20 days, half of the seedlings were inoculated with 4,000 M. javanica eggs. After 60 days, the vegetative parameters, P absorption, essential oil composition, nematode population density, AMF root-colonization efficiency, and AMF spore density were determined. The presence of AMF increased the basil’s fresh weight and ability to absorb P, while reducing the M. javanica reproduction. In total, 21 compounds were identified in basil essential oil, the concentrations of which varied according to the treatments. The major components were eucalyptol, linalool, eugenol, β-elemene, trans-α-bergamotene, and τ-cadinol. Inoculation with AMF decreased the linalool levels but increased the amount of eucalyptol. Mycorrhizal plants showed increased shoot height, P uptake, and essential oil yield and a decreased nematode population density in their roots

Biodiversity Arbuscular Mycorrhizal Fungi in the Former Gold Mine Area in North Sumatra

This study aims to determine the diversity of arbuscular mycorrhizal fungi in the area of the former gold mine in North Sumatra. This research was conducted with 5 soil sampling points. The research method used began with calculating the percentage of root colonization, spores density of arbuscular mycorrhizal fungi and types of arbuscular mycorrhizal fungal spores. In addition, physical and chemical conditions of the soil are also measured. The results showed that the rate of root colonization was at moderate to high with an average rate of root colonization at 22.8%. The density of arbuscular mycorrhizal fungi spores in this study averaged 10/50 g of sample soil. the number of spores in this study belongs to the moderate category, however the characteristics of the study location show the uniqueness of its own area that makes the population of mycorrhizal types not too much. Spore types were found in 4 types with each Glomus and Acaulospora. The conclusion obtained that there was a symbiosis between fungi and plants in the former gold mining area in North Sumatra.

Effect of land use type on arbuscular mycorrhizal fungi diversity in high altitude of Karo Highland

This study evaluated the spore density and diversity of arbuscular mycorrhizal fungi (AMF) in different land use type at Karo Highland. Sampling of soil AMF was conducted once as a material for trap culture by using Pueraria javanica as a host. The trap culture was used to observe the spore density and percentage of root colonization. The results showed that spore density and AMF colonization was not affected by different land use type, but rather by soil chemical properties. Soil acidity and phosphorus content had negative effect on root abundance and colonization, while carbon, nitrogen and potassium content gave positive effects. This study found 15 AMF spores from all types of land use dominated by Glomaceae followed by Acaulosporaceae and Gigasporaceae. The occurrence of AMF species was not specific to one type of land use but rather evenly dispersed in all types.

Colonization by arbuscular mycorrhizal fungi improves salinity tolerance of eucalyptus (Eucalyptus camaldulensis) seedlings

Soil salinity affects soil quality and reduces plant performance. Arbuscular mycorrhizal fungi (AMF) can enhance the tolerance of plants under salinity stress. Cultivation of eucalyptus (Eucalyptus camaldulensis), which exhibits high water use efficiency, is possible in saline areas to produce raw materials for the pulp industry. We determined the effects of arbuscular mycorrhizal fungi (AMF) on the growth and survival of eucalyptus seedlings under saline conditions. Three different clones of eucalyptus seedlings were pre-inoculated with three salt-tolerant AMF species, namely Glomus sp.2, Gigaspora albida and G. decipiens, and without pre-inoculation. The seedlings were grown in a greenhouse for 45 days. They were then transferred to individual pots, filled with field soil and subsequently treated with NaCl solution until electro-conductivity (EC) reached 10, 15 and 20 dS m−1. They were watered for 90 days under nursery conditions. The results show that increased salinity levels reduced plant performance, fractional AMF root colonization, spore number, and eucalypt K/Na ratio. AMF significantly increased chlorophyll and decreased leaf proline concentrations by more than 50% and 20% respectively and increased the K/Na ratio three- to six-fold compared with non-inoculated plants. Pre-inoculation with AMF before outplanting also improved plant performance by more than 30% under salinity stress compared to non-inoculated plants. We conclude that AMF can alleviate the negative impacts of salinity on plant physiological and biochemical parameters.

Long-term Fertilization with Liquid Cattle Manure Leaves Legacy Nutrients, but not Organic Carbon and Has No Effect on Soil Microbial and Physical Properties a Year after Last Application

ABSTRACT Long-term liquid cattle manure (LCM) application can enhance soil fertility, increase soil organic carbon, and improve soil properties. We investigated the residual effects of long-term fertilization with LCM on physical, chemical and microbial properties of a calcareous soil. The effects of LCM, common inorganic fertilization, recommended fertilization or non-fertilized control were investigated in field plots with corn (Zea mays L.), 1 year after the cessation of 16-years of experimentation. The residual concentrations of soil available P, K, Cu, Zn, B and total N but not NO3-N remained significantly higher with LCM, while there were no differences in soil pH, electrical conductivity and sodium adsorption ratio, compared to the other treatments. The previously observed increase of soil organic C with LCM was no longer evidenced. For aggregate size distribution and stability, microbial biomass N, easily extractable glomalin-related soil protein, number and morphotypes of arbuscular mycorrhizal fungal spores and percentage of root length colonization, there was no difference among treatments. Microbial growth and activity were limited by C, while the calcareous nature of the soil was more important than glomalin for soil aggregation. In conclusion, the residual effects of LCM were limited to soil nutrient increase.

Influence of Land Use Intensity and Management on Arbuscular Mycorrhizal Fungi-Avocado Symbiosis

This study was done to assess the effect of soil disturbance on arbuscular mycorrhizal fungi spore abundance and root colonization in avocado (Persea americana Mill.). Rhizosphere soil and root samples of avocado were collected from different farms in south Florida and analyzed for degree of mycorrhizal colonization in roots, spore density and diversity in soil along with soil characteristics. There was significant difference in the soil characteristics among the different farms. Similarly, there was a significant difference in the degree of mycorrhizal colonization in the roots and the arbuscular mycorrhizal fungi spore morphotypes among different land use and management practices. However, there was no significant difference in the total number of arbuscular mycorrhizal fungi spores among these sites. There was no correlation between the number of arbuscular mycorrhizal fungi spores and soil characteristics. However, arbuscular mycorrhizal fungi colonization in roots were strongly influenced by soil characteristics such as soil moisture, carbon, nitrogen, and organic matter. Further research is necessary to identify these AMF species and determine the role of in avocado growth tolerance to anthropogenic disturbance in highly disturbed urban soils.

Increasing flavonoid concentrations in root exudates enhance associations between arbuscular mycorrhizal fungi and an invasive plant

Many invasive plants have enhanced mutualistic arbuscular mycorrhizal (AM) fungal associations, however, mechanisms underlying differences in AM fungal associations between introduced and native populations of invasive plants have not been explored. Here we test the hypothesis that variation in root exudate chemicals in invasive populations affects AM fungal colonization and then impacts plant performance. We examined flavonoids (quercetin and quercitrin) in root exudates of native and introduced populations of the invasive plant Triadica sebifera and tested their effects on AM fungi and plant performance. We found that plants from introduced populations had higher concentrations of quercetin in root exudates, greater AM fungal colonization and higher biomass. Applying root exudates more strongly increased AM fungal colonization of target plants and AM fungal spore germination when exudate donors were from introduced populations. The role of root exudate chemicals was further confirmed by decreased AM fungal colonization when activated charcoal was added into soil. Moreover, addition of quercetin into soil increased AM fungal colonization, indicating quercetin might be a key chemical signal stimulating AM fungal associations. Together these results suggest genetic differences in root exudate flavonoids play an important role in enhancing AM fungal associations and invasive plants’ performance, thus considering root exudate chemicals is critical to unveiling mechanisms governing shifting plant-soil microbe interactions during plant invasions.

Differences in phenolics produced by invasive Quercus rubra and native plant communities induced changes in soil microbial properties and enzymatic activity

Invasive trees can alter soil properties and ecosystem functioning by producing phenolic compounds. Phenolics can influence carbon and nitrogen availability as well as enzymatic activity or act as signaling molecules. In plant-microorganism interactions, species-specific phenolics can be the source of food or toxicity. They may have antimicrobial, stimulatory or both (ambiguous) properties and thus affect soil microbial properties, enzymatic activity, and plant-soil feedbacks differently. We hypothesized that phenolic compounds with antimicrobial properties produced by invasive Quercus rubra would reduce soil microbial biomass and enzymatic activity, and alter microbial community structure. We expected these changes to be most pronounced in the soil organic horizon as they are driven by litter chemistry. We tested changes, potentially associated with the concentrations of 12 phenolic compounds in Q. rubra litter and soil, in microbial properties (respiration rate, bacterial and fungal biomass), enzymatic activity, and microbial community structure in organic and mineral soil horizons as well as in arbuscular mycorrhizal fungi (AMF) spore number and species richness in mineral soil horizon. We found that Q. rubra reduced several soil parameters, namely respiration rate, phosphatase activity, total microbial biomass, bacterial (both G + and G–) biomass, and 16:1ω5 NLFA AMF storage lipid marker as well as changed microbial community structure, which supports our hypothesis that the phenolics produced by Q. rubra have mostly toxic effect on native soil communities. However, Q. rubra did not affect arylsulfatase and urease activity, saprotrophic fungi population, and the number of AMF spores and species. The changes in soil microbial properties and enzymatic activity may be related to high amounts of ellagic acid, ferulic acid, phloridzin, and syringic acid provided with newly shed Q. rubra litter to the soil surface. Some phenolics found in soil, i.e., phloridzin and (–)-epicatechin, correlated negatively, while others, i.e., quercetin and chlorogenic acid, correlated positively with soil microbial parameters and/or enzymatic activity, which suggest either antimicrobial or stimulatory properties of these compounds. Our study demonstrated that invasive Q. rubra has multiple potential effects on soil microbial communities, which can mediate plant-soil feedbacks. Future research should address the long-term consequences of these changes for forest ecosystems and the fitness of native flora.

Efecto Bioprotector de Micorrizas Arbusculares en la Reducción de Roya (Hemileia vastatrix) en la Región San Martín

La roya es un problema generalizado que ha afectado a diferentes países de América Latina, generando pérdidas económicas en los productores cafetaleros. Se evaluó el efecto de los hongos micorrízicos arbusculares (HMA), sobre la presencia de roya (Hemileia vastatrix) en plantas de café. Se empleó un Diseño Completamente al Azar con dos factores: fuentes de inóculo HMA e Inoculación de roya, incluyendo tratamiento testigos (absoluto e infestado); se usó como sustrato tierra agrícola y arena (2:1); se inoculó plantas de café con 1 500 esporas de HMA procedente de Rioja, Lamas, Dorado y Huallaga, posteriormente se inóculo con esporas de roya; se evaluaron altura de planta, área foliar, biomasa seca y aérea, incidencia, severidad, colonización micorrízica y longitud de micelio extraradical. Los resultados mostraron que los tratamientos inoculados con HMA presentaron mejoras incrementos en morfología, micorrización y menor incidencia y severidad a roya.

Arbuscular Mycorrhiza and Sustainable Agriculture

Arbuscular mycorrhizal fungi (AMF) provide benefits to most crop species via enhanced nutrient uptake, increased drought and abiotic stress resistance, and reduced effects of pathogens and pests. Much remains unclear regarding the specific mechanisms influencing these processes, and the critical roles of AMF are often overlooked in planning agroecological systems. There is growing consensus, however, around the important roles AMF play in improving plant resilience and crop yield while also enhancing the functioning of soil microbial communities. Heterogeneous practices across all scales complicate the successful integration of AMF in agroecological systems. AMF symbioses with crops are passive, or stimulated by incorporation of crop wastes in soil, soil inoculation with AMF spores, or the planting inoculated of seeds. Here we suggest that AMF can have highest beneficial impacts in areas with low levels of agrochemical inputs. We argue that areas with intensive agrochemical inputs can also be made more sustainable with AMF enhancements.