Root Colonization Research Articles

Co-applications of Rhizobium and arbuscular mycorrhizal fungi synergistically alleviate heavy metal uptake and toxicity in lentil plants (Lens culinaris Medik.) grown in sewage sludge amended soil

Reusing sewage sludge as a mode of nutrients and an organic amendment may be a viable choice for the appropriate treatment of organic waste. This study examined the impact of symbiotic microbes such as Rhizobium and two selected arbuscular mycorrhizal fungi (AMF), Funneliformis caledonius (Nicolson & Gerd.) and Glomus bagyarajii (Mehrotra), on the growth, photosynthetic pigments, biochemical content, microbial population, and heavy metal uptake in lentil plants grown in soil mixed with 20 % sewage sludge. Lentil seeds were inoculated with Rhizobium prior to sowing and with either of the AMF (Funneliformis caledonius or Glomus bagyarajii) in pots filled with soil-sewage sludge mixture. The results showed that the tested microbial inoculum enhanced the growth and productivity of lentil plants. Lentil plants inoculated with Rhizobium and AMF had better nodulation and root colonization, leading to an increase in the nitrogen, phosphorus and potassium (NPK) content and a decrease in the stress marker, proline, in plant parts. In addition, the inoculated microbes also improved the photosynthetic and biochemical contents of the plant. Lentil plants grown in sewage sludge-amended soil when inoculated with Rhizobium and either of AMF were found to be more effective in accumulating Cd, Cr, Pb, Ni, and Zn in the roots, while restricting their translocation to the above-ground parts of the plant, thereby improving plant health. Overall, the study outcomes provide evidence that Rhizobium and AMF have the potential to tolerate heavy metal stress caused by the addition of sewage sludge to soil, which has important implications for sustainable agriculture practices. The study also highlights the importance of microbial inoculants, such as Rhizobium and AMF in enhancing growth and yield, particularly under heavy metal stress in economically important lentil.

Use of manganese oxide nanoparticle (MnO2 NPs) and Pseudomonas putida for the management of wilt disease complex of carrot

Wilt disease complex of carrot is caused by Ralstonia solancearum and Meloidogyne incognita and is responsible for considerable yield loss. Manganese oxide nanoparticle (MnO2 NPs) and Pseudomonas putida were used alone and in combination for the management of wilt disease complex. In vitro, MnO2 NPs 0.10 g.L-l caused 49.36% reduction in hatching and 14.23% mortality of second stage juveniles (J2) of M. incognita while paper disc dipped in MnO2 NPs suspension caused 0.51 mm inhibition zone around R. solanacearum in nutrient agar medium. Inoculation of P. putida to plants with pathogens caused a similar increase in plant growth, chlorophyll and carotenoid contents as caused by foliar spray with 0.10 g.L−1 MnO2 NPs. Use of P. putida with NPs foliar spray to plants with pathogens caused a greater increase in plant growth, chlorophyll and carotenoid contents than with P. putida or NPs foliar spray. Inoculation of M. incognita/R. solanacearum/M. incognita plus R. solanacearum/P. putida/MnO2 NPs and MnO2 NPs plus P. putida caused increase in proline contents. Root colonization by P. putida was reduced in plants with test pathogens. Foliar application of MnO2 NPs and P. putida reduce wilt disease indices. Galling and populations of M. incognita was also reduced in plants co-inoculated with R. solanacearum. The greatest reduction in nematode populations and galling was observed in plants with NPs spray together with P. putida. Principal component analysis demonstrated a clear influence of NPS and P. putida and their combination on various studied parameters in diseased plants.

Pervasive associations between dark septate endophytic fungi with tree root and soil microbiomes across Europe

Trees interact with a multitude of microbes through their roots and root symbionts such as mycorrhizal fungi and root endophytes. Here, we explore the role of fungal root symbionts as predictors of the soil and root-associated microbiomes of widespread broad-leaved trees across a European latitudinal gradient. Our results suggest that, alongside factors such as climate, soil, and vegetation properties, root colonization by ectomycorrhizal, arbuscular mycorrhizal, and dark septate endophytic fungi also shapes tree-associated microbiomes. Notably, the structure of root and soil microbiomes across our sites is more strongly and consistently associated with dark septate endophyte colonization than with mycorrhizal colonization and many abiotic factors. Root colonization by dark septate endophytes also has a consistent negative association with the relative abundance and diversity of nutrient cycling genes. Our study not only indicates that root-symbiotic interactions are an important factor structuring soil communities and functions in forest ecosystems, but also that the hitherto less studied dark septate endophytes are likely to be central players in these interactions.

Defense responses and symbiotic functional initiation in trifoliate orange‒arbuscular mycorrhizal fungi interaction

Arbuscular mycorrhizal fungi (AMF) trigger beneficial effects on their hosts, but it is unknown how plants modulate their defense responses during root colonization of AMF and the symbiotic benefits are initiated. The purpose of this study was to analyze the root mycorrhizal colonization process of trifoliate orange and the responsive patterns of plant growth, root peroxide hydrogen (H2O2), antioxidant enzymes and their encoding gene expression, and sugar, lipid and phosphate transporter protein gene expression at 7‒56 days of inoculation (doi) with Funneliformis mosseae (Fm). Fm developed appressoriums on the root surface at 7 doi, followed by abundant arbuscules in root cortical cells at 28 doi, intracellular vesicles at 42 doi, and root mycorrhizal colonization rate of 41.54% at 56 doi. Plant growth improvement by Fm started at 28 doi. The immune defense response of roots was initiated at 7 doi, as evidenced by the increase of H2O2 levels and superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity, as well as the up-regulation of PtMn-SOD, PtCu/Zn-SOD, PtPOD, and PtCAT expression, which lasted until 14 doi. Starting at 28 doi, a sugar transporter gene (PtSWEET), a lipid transporter gene (PtSTR), and a phosphate transporter gene (PtPT6) were initiated to be up-regulated, followed by the up-regulation of PtSTR2, PtPT3, and PtPT5 at 42 doi and PtFe-SOD at 56 doi. Arbuscule formation and plant growth improvement together at 28 doi suggested that arbuscules trigger improved growth responses of host plants. This study also reveals the initiation of host immune defense response and function in early root AMF colonization.Graphical

Arbuscular mycorrhizal fungi and phosphorus affect Araucaria angustifolia seedling growth

Symbioses between plants and arbuscular mycorrhizal fungi (AMF) provide many advantages, including a reduced need for fertilization. In this study, the effects of AMF inoculation and phosphorus application on the growth and nutritional status of Araucaria angustifolia seedlings were evaluated. The treatments included inoculation with AMF (Gigaspora margarita, Rhizophagus intraradices, Acaulospora colombiana, Acaulospora scrobiculata, or Dentiscutata heterogama), inoculation with a mixture of AMF in 100 g of 50-year-old araucaria forest soil, application of two doses of P2O5 (25 or 100 mg kg-1), and the control. A completely randomized design was used, with seven replicates per treatment. The growth parameters, macronutrient and micro-nutrient contents, root colonization, and mycorrhizal effects on the extracted nutrients were evaluated at 75 and 150 d post germination. Analysis of variance, correlations, and principal component analysis (PCA) were used to evaluate that data. Inoculation with AMF had favorable effects on growth parameters, root colonization, and the extraction of macronutrients and micro-nutrients. In particular, the mixture of AMF from the 50-year-old araucaria forest soil, R. intraradices, and A. colombiana were beneficial. Similarly, the application of 25 mg of P2O5 significantly affected the growth of A. angustifolia seedlings compared to other treatments and increased the efficiency of root colonization.

Micorrizas arbusculares em pomares de mangueira no semiárido brasileiro: influência da fenologia, do manejo e da variedade

ABSTRACT: Arbuscular mycorrhizal fungi (AMF) increase the absorption surface of roots, providing greater absorption of water and nutrients from the soil by plants. Thus, it is important to know how arbuscular mycorrhizae are affected by factors such as phenology, management and varieties in mango (Mangifera indica) orchards in the irrigated semi-arid region. With this objective, soil and root samples were collected during the vegetative, flowering and fruiting stages, and in the water stress period before flowering, always on the same trees. The study was carried out in mango orchards of the Keitt and Palmer varieties, in agricultural farms located in Juazeiro - BA and Petrolina - PE, both under conventional management (with fertilizers and paclobutazol). The soil was used to quantify the number of AMF spores and phosphorus content. Mycorrhizal colonization in roots was evaluated in qualitative terms (presence of hyphae, vesicles and arbuscles) and quantitative terms (% of colonization). Total mycorrhizal colonization was high, with averages above 65%, and higher values in the fruiting period. Colonization by vesicles and arbuscles was on average above 45% and 17%, respectively, with higher means also during fruiting. The number of AMF spores in the soil averaged over 130 spores in 50 g of soil, with higher values in the period of water stress. The phosphorus content in the soil did not influence mycorrhizal colonization and the number of spores in the soil. The association of AMF with mango trees was generally affected by management and phenology, regardless of the cultivated varieties.

Función de los hongos micorrícicos y las bacterias solubilizadoras de fosfatos en la absorción de elementos esenciales y metálicos en las plantas en suelos contaminado con metales pesados

The objective of this study was to compare the effect of different types of inoculants (control, vesicular arbuscular mycorrhizae fungi [VAMF], phosphate-solubilizing bacteria [PSB], and co-inoculant [VAMF-PSB]) on root colonization, plant growth, macronutrient (P and N) uptake, and metal element uptake under heavy metal-contaminated soil conditions. Three species of vegetable plants, namely tomato (Solanum lycopersicum L. cv. Ratna), red chili (Capsicum annuum L. cv. Gada), and hot chili (Capsicum frutescens L. cv. Pusaka Brengolo), were grown in heavy metal (Zn, Ca, Ni and Cd) –contaminated soil for eight weeks. Plants co-inoculated with VAMF-PSB showed significantly higher root colonization by VAMF as well as P and N concentrations in shoot and root than plants inoculated with only VAMF or PSB; consequently, the plant biomass also increased. In heavy metal-contaminated soil, VAMF colonization and PSB application could significantly improve the essential metal concentration (Cu and Zn) in the shoot, although there were no significant effects on the roots. On the contrary, co-inoculation with VAMF-PSB could significantly decrease Cd and Ni concentrations in the shoot, although Cd and Ni concentrations did not show a significant difference in the root. The concentrations of Cu, Zn, Cd, and Ni were higher in the roots than in the shoots of the three plant species tested. The type of inoculant used in this study selectively discriminated between plant essential (Cu, Zn) and non-essential elements (Cd, Ni).

Effects of a dark septate endophyte and extracellular metabolites on alfalfa root exudates: a non‐targeted metabolomics analysis

AbstractDark septate endophytes (DSE) are widespread colonizers of plant roots and have important ecological functions such as the regulation of plant growth and nutrient uptake. The mechanisms by which DSE mycelium and its extracellular metabolites promote plant growth have not yet been determined. Here, the growth‐promoting effects of DSE mycelium (H) and extracellular metabolites (M) on alfalfa (Medicago sativa L.) were investigated. Treatments H, M and HM increased the total biomass of alfalfa by 23.9%, 47.2% and 47.1%, respectively. H and M modified root structure by increasing root volume and reducing root tissue density, and promoting nutrient uptake. Metabolomic analysis indicates that alfalfa root exudates contained 204 metabolites of different types, mainly lipids and lipid‐like molecules, organic acids and derivatives, benzenoids. There were more organoheterocyclic compounds and fewer organic acids and derivatives in root exudates in treatment H than in treatment M. Pathway analysis shows that DSE and its extracellular metabolites had greater effects on glycerophospholipid metabolism and N‐glycan biosynthesis pathway. The results provide information on the mechanisms involved in the metabolic regulation of plant growth promotion by DSE.

Arbuscula Mycorrhizal Fungi on The Rhizosphere Three in The Ex-Sand Mine at Cipancur-Kuningan West Java

Sand and stone mining activities in Kuningan Regency cause damage to soil and environmental ecosystems, so reclamation and revegetation are carried out. The purpose of this study is to determine the existence of indigenous / local Arbuscular Mycorrhizal Fungi (FMA) found in the rhizozofer stands of Sengon (Paraserianthes falcataria) and Acacia (Acacia mangium) which are revegetation plants on the land of former sand and stone mines Cipancur village, Kalimanggis district, Kuningan regency. Sampling using the composite sampling method, FMA isolation technique using the wet pour method is then continued with the centrifugation technique and root colonization observation technique using the root staining technique (staining). The temperature of the ex-mining soil ranges from 28C – 29C, the soil pH is 5.5 including acidic, the soil moisture varies between wet, medium (slightly wet) and dry (dry) but during the rainy season the soil will become wet and even flooded. The results showed that there were 5 genera, it are Acaulospora, Glomus, Gigaspora, Sclerocytis and Scutellospora. The dominant genus is Glomus. The highest spore density was found in Sengon stands with 1,157 spores per 50 grams of soil. The highest percentage of AMF infection was at the root of Sengon stands at 69% from the ex-sand mining area.

Osmotolerant plant growth promoting bacteria mitigate adverse effects of drought stress on wheat growth.

Drought stress represents a major constraint with significant impacts on wheat crop globally. The use of plant growth-promoting bacteria (PGPB) has emerged as a promising strategy to alleviate the detrimental impacts of water stress and enhance plant development. We investigated 24 strains from diverse ecosystems, assessed for PGP traits and tolerance ability to abiotic stresses (drought, salinity, temperature, pH, heavy metals, pollutants, herbicides, and fungicides). The most effective bacterial strains Providencia vermicola ME1, Pantoea agglomerans Pa, Pseudomonas knackmussi MR6, and Bacillus sp D13 were chosen. Furthermore, these strains exhibited PGP activities under osmotic stress (0, 10, 20, and 30% PEG-6000). The impact of these osmotolerant PGPBs on wheat (Triticum durum L.) growth under drought stress was assessed at two plant growth stages. In an in vitro wheat seed germination experiment, bacterial inoculation significantly enhanced germination parameters. In pot experiments, the potential of these bacteria was evaluated in wheat plants under three treatments: Well-watered (100% field capacity), moderate stress (50% FC), and severe stress (25% FC). Results showed a significant decline in wheat growth parameters under increasing water stress for uninoculated seedlings. In contrast, bacterial inoculation mitigated these adverse effects, significantly improving morphological parameters and chlorophyll pigment contents under the stress conditions. While malondialdehyde (lipid peroxidation) and proline contents increased significantly with drought intensity, they decreased after bacterial inoculation. The antioxidant enzyme activities (GPX, CAT, and SOD) in plants decreased after bacterial inoculation. The increased root colonization capacity observed under water stress was attributed to their ability to favorable adaptations in a stressful environment. This study highlighted the potential of selected PGPB to alleviate water stress effects on wheat, promoting practical applications aimed at enhancing crop resilience under conditions of water shortage.

OsCBL1 mediates rice response to local nitrate signaling: insights into regulatory networks and gene expression.

Nitrate is a significant source of nitrogen in soils and also serves as a critical signal for root development. Previous studies have demonstrated that the local nitrate supply promotes lateral root elongation primarily through local nitrate signals, rather than nutritional effects. In this study, we report that Calcineurin B-like protein 1 (OsCBL1) positively regulates local nitrate signaling, thereby triggering lateral root colonization, as revealed by a comparative analysis of the phenotype and whole transcriptome of the knockdown mutant (OsCBL1-KD) and the wild-type (WT). In the split-root system, the knockdown of OsCBL1 was found to inhibit local nitrate-induced lateral root growth. Transcriptome analyses identified 398 differentially expressed genes (DEGs) that were under the control of OsCBL1 and associated with the phenotype of nitrate-induced lateral root colonization. Further analysis revealed that the nitrate transporter/sensor gene OsNRT1.1B was up-regulated under Sp-NaNO3 conditions compared to Sp-NaCl in WT but not in OsCBL1-KD plants. Pathway mapping of DEGs (i.e., genes exhibiting a significant change in expression in the Sp-NaNO3 condition compared to the Sp-NaCl condition) revealed a preferential upregulation of genes involved in lignin biosynthesis and a downregulation of genes involved in auxin and salicylic acid signaling. This suggests that OsCBL1 might function as a transmitter within the auxin, salicylic acid signaling, lignin biosynthesis, and nitrate sensor (OsNRT1.1B)-mediated pathways in response to local nitrate signaling. We also identified a transcriptional regulatory network downstream of OsCBL1 in nitrate-rich patches that is centered on several core transcription factors. Our study provides new insights into how plants adapt to an inhomogeneous distribution of nitrogen in the soil.

Inoculation of tomato roots with single and mixed suspensions of Trichoderma harzianum ITEM 3636 conidia and Pseudomonas putida PCI2 cells

ABSTRACT Mixes of compatible beneficial microorganisms can perform better than single strains to support plant health and growth. This study examined effects of inoculating tomato (Solanum lycopersicum L.) roots with individual and mixed suspensions of Trichoderma harzianum ITEM 3636 and Pseudomonas putida PCI2 on growth and yield in field assays. Culture filtrates were used to observe in vitro compatibility between strains. Effects of ITEM 3636 on tomato seedlings in vitro were studied. Scanning electron microscopy was used to examine root colonization by the bacterial and fungal strains. ITEM 3636 was compatible with PCI2 and improved root density in vitro. When compared to other treatments, co-inoculation of tomato plants consistently resulted in increases in the number of fruit and yield under field conditions. Co-inoculating tomato roots during transplanting with the studied microorganisms may improve plant survival and increase productivity.

Keanekaragaman Fungi Mikoriza Arbuskula pada Tegakan Kelicung (Diospyros macrophylla Blume) di KHDTK Rarung, Lombok Tengah

Kelicung tree (Diospyros macrophylla) is a native tree species of West Nusa Tenggara. It is a slow-growing tree with very good wood ornament, strength, and durability properties. Symbiotic mutualism between kelicung and mycorrhiza has not been documented. Mycrorrhiza is a mutualism symbiosis between fungi and plant roots that could improve plant growth due to increase nutrient and water absorbtion. Therefore, the objective of this study is to investigate mycorrhizal symbiosis in kelicung roots. Soil and root samples were taken in the Rarung Special Purpose Forest Area at 0 – 20 cm depth. Isolation and identification of arbuscular mycorrhizal fungi used screening and centrifugation methods to identify spore density, diversity, abundance, and frequency. Furthermore, root staining and colonization of arbuscular mycorrhizal fungi were carried out by observing the structure of vesicles, arbuscules, hyphae, and spores on Kelicung roots. The research results showed that the average number of spores found was 846 spores/50 g of soil. Spores were identified in two genera: Glomus sp and Acaulospora sp. Glomus spores found were round, the colour of the spores was yellow, the spores did not react when Melzer's solution was dropped, and the spore walls of the Arbuscular mycorrhizal fungi of the genus Glomus consisted of 1-2 layers of cell walls. Observation of root colonization, no structures of root arbuscular mycorrhizal fungi were found in Kelicung.
 Keywords: Acaulospora sp., Arbuscular mycorrhizal fungi, Diospyros macrophylla, Glomus sp., Kelicung

Adjuvant Pluronic F68 Is Compatible with a Plant Root-Colonizing Probiotic, Pseudomonas chlororaphis O6

Plant probiotic bacteria are being increasingly used to maximize both the productivity and quality of field crops. Pseudomonas chlororaphis O6 (PcO6) is a plant root colonizer with probiotic activities. This bacterium produces an array of metabolites, including a group of phenazines that are functional in plant protection. The paper reports responses of PcO6 to a nonionic triblock copolymer surfactant, Pluronic F68. This Pluronic exhibits membrane “healing” activity and improves cryopreservation recovery in eukaryotic cells. The product is FDA-approved and is applied as an adjuvant in formulations used in agriculture, medicine, and biotechnology. Growth of PcO6 on lysogeny broth at 25 °C was unhindered by 0.1 and 1.0 g/L F68, reduced at 10 g/L, and with significant inhibition at 100 g/L F68; micelle formation could account for inhibited growth at higher doses. Phenazine production was not changed by F68, whereas the surfactant activity of F68 induced the spread of bacterial colonization on 0.5% agar. Exposure of cells to fluorescein-labeled F68 resulted in intense fluorescence, stable to washing, showing a direct association of the Pluronic with the bacterium. However, neither protection nor harm was found for PcO6 cells suspended in either 0.1% or 1% F68 after three freeze (−20 °C)/thaw cycles. These findings suggest that F68 could be compatible for use in agricultural formulations with little effect on probiotics such as PcO6.

Mycorrhiza-triggered changes in leaf food quality and secondary metabolite profile in tea at low temperatures

Tea is a popular cash crop around the world that often endures low temperatures in the spring, thereby negatively affecting tea yield and quality. The objective of this study was to examine the effects of an arbuscular mycorrhizal fungus, Clariodeoglomus etunicatum, on plant growth, root morphology, leaf food quality, associated gene expression, and secondary metabolite profiles in tea (Camellia sinensis cv. Fuding Dabaicha) seedlings grown at low temperatures. A seven-day low temperature (4 °C) treatment significantly reduced root colonization rate by C. etunicatum by 21.08%. Uninoculated plants' growth was considerably impeded by low temperatures, whereas C. etunicatum inoculation significantly increased leaf number and leaf, stem and root biomass at low temperatures. Low temperatures had little effect on root morphology, whereas C. etunicatum inoculation significantly increased root surface area at low temperatures. In addition, low temperatures reduced leaf quality variables, whereas C. etunicatum significantly increased the levels of glucose, fructose, sucrose, tea polyphenols, catechin, free amino acids, and caffeine at low temperatures, along with up-regulated expression of CsGDH, CsGOGAT, and CsHMGR, as well as down-regulated expression of CsGs. Non-targeted metabolomics identified 767 differential metabolites, of which 65 differential metabolites were observed at low temperatures by C. etunicatum inoculation, including 42 (e.g., catechin, (−)-epicatechingallate, protoanemonin, epicatechin, and 4-dodecylbenzenesulfonic acid) up-regulated and 23 (e.g., 4-hydroxybenzoic acid, raffinose, L-theanine, melezitose, and D-serine) down-regulated. Mycorrhiza-triggered differential metabolites enriched 268 metabolic pathways at low temperatures, including isoquinoline alkaloid biosynthesis, lysine biosynthesis, tyrosine metabolism, and others. These findings reveal that C. etunicatum can function as a fungal stimulant to improve the plant growth and leaf quality in tea while also changing the secondary metabolite profile at low temperatures.

The role of mycorrhiza and humic acid on quantitative and qualitative traits of faba bean plant under different fertilizer regimes

In sustainable agricultural ecosystem management, a key focus is on minimizing chemical fertilizer use and maximizing the use of non-chemical alternatives. Our study was designed to explore the impact of mycorrhizal fungi and humic acid (HA) on the quantitative and qualitative characteristics of faba beans under varying chemical fertilizer levels. The experiment involved different treatments, which included HA and mycorrhiza in four variations (control, HA, HA+ mycorrhiza, and mycorrhiza alone), and nitrogen, phosphorus, and potassium (NPK) fertilizers at three different dosages (50%, 75%, and 100% of the recommended amount). The findings revealed that combining HA with mycorrhiza significantly influenced root colonization, with the highest chlorophyll a concentration (1.58 mg g⁻¹) observed in the HA+ mycorrhiza treatment at 75% NPK. This treatment also led to the highest counts in seeds per pod, number of pods, and weight of 100 seeds. Between the 100% and 75% NPK levels in the HA+ mycorrhiza treatment, no significant differences were noted in terms of grain and biological yield. The greatest grain yields were measured at 4356 kg ha⁻¹ and 4322 kg ha⁻¹ for the HA+ mycorrhiza treatment at 100% and 75% NPK, respectively. Additionally, the highest concentrations of Fe, N, P, K, and Zn were observed with the HA+ mycorrhiza application at the 100% NPK level.

Endophytic microbiota and ectomycorrhizal structure of Alnusglutinosa Gaertn. at saline and nonsaline forest sites

The tolerance of European alder (Alnusglutinosa Gaertn.) to soil salinity can be attributed to symbiosis with microorganisms at the absorptive root level. However, it is uncertain how soil salinity impacts microbial recruitment in the following growing season. We describe the bacterial and fungal communities in the rhizosphere and endosphere of A.glutinosa absorptive roots at three tested sites with different salinity level. We determined the morphological diversity of ectomycorrhizal (ECM) fungi, the endophytic microbiota in the rhizosphere, and the colonization of new absorptive roots in the following growing season. While bacterial diversity in the rhizosphere was higher than that in the absorptive root endosphere, the opposite was true for fungi. Actinomycetota, Frankiales, Acidothermus sp. and Streptomyces sp. were more abundant in the endosphere than in the rhizosphere, while Actinomycetota and Acidothermus sp. dominated at saline sites compared to nonsaline sites. Basidiomycota, Thelephorales, Russulales, Helotiales, Cortinarius spp. and Lactarius spp. dominated the endosphere, while Ascomycota, Hypocreales and Giberella spp. dominated the rhizosphere. The ECM symbioses formed by Thelephorales (Thelephora, Tomentella spp.) constituted the core community with absorptive roots in the spring and further colonized new root tips during the growing season. With an increase in soil salinity, the overall fungal abundance decreased, and Russula spp. and Cortinarius spp. were not present at all. Similarly, salinity also negatively affected the average length of the absorptive root. In conclusion, the endophytic microbiota in the rhizosphere of A.glutinosa was driven by salinity and season, while the ECM morphotype community was determined by the soil fungal community present during the growing season and renewed in the spring.

Fine root presence and increased phosphorus availability stimulate wood decay in a central Amazonian rainforest

In the Amazon basin, approximately 60% of rainforest thrives on geologically old and highly weathered soils, thus decomposition represents an important mechanism for recycling nutrients from organic matter. Although dead logs and branches constitute up to 14% of the carbon stored in terrestrial ecosystems, woody debris decomposition and mainly the effect of direct nutrient cycling by plant root interaction is poorly studied and often overlooked in ecosystem carbon and nutrient budgets. Here we monitored the decomposition of five different local woody species covering a range of wood density by conducting a long‐term wood decomposition experiment over two years with factorial root presence and phosphorous (P) addition treatments in a central Amazonian rainforest. We hypothesized that woody debris decomposition is accelerated by colonizing fine roots mining for nutrients, possibly strongly affecting wood debris with lower density and higher nutrient concentration (P). We found that root colonization and P addition separately increased wood decay rates, and although fine root colonization increased when P was added, this did not result in a change in wood decay. Nutrient loss from wood was accelerated by P addition, whereas a root presence effect on nutrient mobilization was only detectable at the end of the experiment. Our results highlight the role of fine roots in priming wood decay, although direct nutrient acquisition by plants seems to only occur in more advanced stages of decomposition. On the other hand, the positive effect of P addition may indicate that microbial nutrient mobilization in woody material is driven mainly by wood stoichiometry rather than priming by root activity.

Earthworms as conveyors of mycorrhizal fungi in soils

Earthworms are emblematic soil organisms, known to be highly beneficial to soil functioning and ecosystem sustainability. In the current context of agroecological transition, they can be inoculated in degraded soil for their beneficial effect on soil structure and plant growth. We here advocate that earthworms can be also used as conveyors of beneficial mycorrhizal fungi in soils, thus enhancing plant nutrition and promoting primary production. Through a review of the literature on earthworms and mycorrhizal fungi, this paper aims at answering the following questions: Do earthworms ingest mycorrhizal fungi? Do they convey mycorrhizal fungi in their digestive tube so they are still active when leaving earthworm intestines? Is there a spatial correlation between earthworm casts and plant roots which could enhance mycorrhizal colonization of the root system? Considering that earthworms may ingest, transport, keep active in their intestine and bring mycorrhizal fungi to the roots, they could be used as conveyors of mycorrhizal fungi in soils. Although depending on the species, their presence was found to improve the colonization of roots by mycorrhizal fungi and to increase significantly the mycorrhization percentage. This perspective paper also underlines precautions that should be taken to make available and relevant this Nature-based soil improvement method.

Genetic transformation of Trichoderma with GUS and Hyg Genes to study root colonisation in Groundnut

A stable β-glucoronidase, hygromycin transformed Trichoderma harzianum was obtained by Agrobacterium mediated transformation.The confirmation was made with PCR and gel electrophoresis. This transformed strain was used to study the activity ofTrichoderma in the groundnut root with the aid of βglucoronidase gene expression. Microscopic analysis revealed Trichoderma colonization and the presence of GUSstained mycelium in the root section.