Arbuscular Mycorrhizal Fungi Strains Research Articles

Physiological and Enzymatic Antioxidant Responses of Solanum tuberosum Leaves to Arbuscular Mycorrhizal Fungal Inoculation under Water Stress.

Solanum tuberosum is one of the most widely cropped plant species worldwide; unfortunately, drought is one of the major constraints on potato productivity because it affects the physiology, biochemical processes, and yield. The use of arbuscular mycorrhizal fungi (AMF) has exhibited beneficial effects on plants during drought. The objective of this study was to analyse the effect of AMF inoculation on two genotypes of potato plants exposed to water stress, and the photosynthetic traits, enzymatic antioxidant activity, and exudation of low-molecular-weight organic acids (LMWOAs) of potato plants inoculated with two strains of AMF, Claroideoglomus claroideum (CC) and Claroideoglomus lamellosum (HMC26), were evaluated. Stomatal conductance exhibited a similar trend in the CC and HMC26 treatments for both potato genotypes; moreover, the photosynthetic rate significantly increased by 577.9% between the 100% soil humidity (S0) and 40% soil humidity (S2) stress levels for the VR808 genotype under the CC treatment. The activities of the enzymes catalase (CAT) and ascorbate peroxidase (APX) showed similar trends. In this study, there were different responses among genotypes and treatments. Inoculation with CC under S2 stress levels is a promising potential approach for improving potato growth under drought conditions.

Improving vanadium removal from contaminated river water in constructed wetlands: The role of arbuscular mycorrhizal fungi

Industrial activities pose a significant ecological risk to water resources as they pollute surrounding waters with vanadium (V). Although the contribution of plants and substrates to V removal in constructed wetlands (CWs) has been reported, the role of arbuscular mycorrhizal fungi (AMF) is unclear. The aim of the present study was to investigate the role of AMF in V removal in CWs and to elucidate the underlying mechanisms. Reed plants (Phragmites australis) were inoculated with an AMF strain (Rhizophagus irregularis) in CW columns, creating AMF-inoculated (+AMF) and non-inoculated (-AMF) treatments. Three levels of influent V concentrations (low: 0.50 mg L−1, medium: 1.14 mg L−1 and high: 1.52 mg L−1) were examined. The + AMF treatment showed higher V removal (60%–98%) than the control (40%–82%) in all three conditions, although the difference was not significant in some cases. The mean mycorrhizal effects were 75%, 19%, and 28% for low, moderate, and high influent V concentrations, respectively. The +AMF treatment showed a higher GRSP-bonded V concentration (5.5 mg g−1) than the -AMF treatment (4.0 mg g−1). Furthermore, +AMF treatment showed larger plants with higher V concentrations in their tissues, accompanied by increased biological concentration factors and biological accumulation factors. Given the remarkable positive effect of AMF on V removal, our study suggests that treating AMF in CWs is a worthwhile approach.

Elevating Sorghum Prosperity: Unveiling Growth Trends through Phosphate-Solubilizing Bacteria and Arbuscular Mycorrhizal Fungi Inoculation in Phosphate-Enriched Substrates

This study aimed to elucidate the impact of phosphate-solubilizing bacteria (PSB) and arbuscular mycorrhizal fungi (AMF) inoculation on sorghum growth within substrates derived from phosphate solid sludge, with the overarching objective of repurposing phosphate sludge to be a viable agricultural substrate. Four PSB strains (Serratia rubidaea, Enterobacter bugandensis, Pantoea agglomerans, Pseudomonas sp.) were meticulously selected from phosphate solid sludge, along with two AMF strains (Rhizophagus intraradices and Funneliformis mosseae), constituting the experimental inocula. Phosphate solid sludge was judiciously blended with peat at varying volumetric proportions (0%, 10%, 20%, 40%, and 60%), providing the matrix for sorghum cultivation, and concomitantly subjected to inoculation with PSB and AMF. Following a meticulously monitored two-month duration, a comprehensive evaluation of diverse morphological parameters, biomass accrual, nitrogen content, total phosphorus concentration, potassium levels, calcium content, and root colonization in sorghum plants was conducted. The empirical findings underscored a discernible decline in the assessed parameters with escalating concentrations of phosphate solid sludge. Particularly noteworthy was the pronounced amelioration observed in plants inoculated with AMF in comparison to both the control and PSB-inoculated counterparts. In conclusion, the application of raw phosphate solid sludge as an agricultural substrate is deemed unsuitable, prompting the imperative need for further in-depth investigations to ascertain the nuanced intricacies underlying these outcomes.

Use of arbuscular mycorrhizal fungi (AMF) in the nutrition of <i>Leucacephala leucocephala </i>(Lam.) De wit for forage production

At present, the use of biofertilizers and protein plants in the nutrition of pastures and forage has increased. The investigation was carried out in the University Center of the municipality of Cumanayagua, county of Cienfuegos, Cuba with the objective of evaluating the response of Leucaena leucocephala (Lam.) De Wit to the inoculation of different arbuscular mycorrhizal fungi (AMF) strains. The experiment was carried out in polyethylene bags. The experiment used a random blocks design with three replicates and the following treatments: #1. Soil (Control treatment, without inoculation and NPK application), #2. Soil + inoculation with the AMF strain F. mosseae/INCAM-2, #3. Soil + inoculation with the AMF strain G. cubense/INCAM-4) and #4. Soil + NPK fertilization at plant establishment application of NPK (25, 40 y 120 kg ha-1 de N, P2O5 y K20) + N at each cut at 70% of the initial dose. The inoculation with AMF was simultaneous for all treatments. A establishment cut and five successive cuts were performed, with 51.33 average days between them. The biomass production, the content of gross protein of L. leucocephala in each harvest and the cumulative total, as well as mycorrhizal effectiveness, were quantified. L. leucocephala positively responded to F. mosseae/INCAM-2 inoculation. Biomass production for cut increased between 31,50 % (Treatment #2) y 19,40 % (Treatment #3) with respect to control treatment. Inoculation with F. mosseae/INCAM-2 showed higher mycorrhizal effectiveness. The highest value in gross protein was obtained in the variant with mineral fertilization and the inoculated variants overcame the control treatment, with better performance than treatment # 2 ( Soil+ Funneliformis mosseae/INCAM-2).

Effects of fungal endophytes and arbuscular mycorrhizal fungi on growth of Echium vulgare and alkannin/shikonin and their derivatives production in roots

Endophytic fungi as well as arbuscular mycorrhizal fungi (AMF) are known to stimulate plant growth and production of secondary metabolites in medicinal plants. Here, 10 endophytic fungi isolated from roots of wild Alkanna tinctoria plants and 5 AMF purchased from the Glomeromycota in vitro collection were evaluated, during two successive three-month greenhouse experiments, on the growth of Echium vulgare and alkannin/shikonin and their derivatives (A/Sd) production in the roots. Some of the endophytic fungi tested significantly increased plant growth parameters as compared to the control: Cladosporium allicinum, Cadophora sp., Clonostachys sp., Trichoderma hispanicum and Leptosphaeria ladina increased root volume, Plectosphaerella sp. And T. hispanicum root fresh weight and root water retention and T. hispanicum plant water retention. However, none of these fungi impacted A/Sd production. Conversely, none of the AMF strains tested impacted plant growth parameters, but those inoculated with Rhizophagus intraradices MUCL 49410 had a significantly higher concentration of alkannin/shikonin (A/S), acetyl-A/S, β,β– dimethylacryl-A/S, isovaleryl-A/S and total A/Sd, compared to the control plants. Further studies are needed to investigate the mechanisms involved in the production of A/Sd in plants associated to specific endophytic fungi/AMF and on the cultivation conditions required for optimal production of these compounds.

Antioxidant Response, Phenolic Compounds and Yield of Solanum tuberosum Tubers Inoculated with Arbuscular Mycorrhizal Fungi and Growing under Water Stress.

Solanum tuberosum (potato) is one of the most common crops worldwide; however, it is sensitive to water stress, which necessitates the identification of alternative tools to improve their production. Here, we evaluated the inoculation of two arbuscular mycorrhizal fungi (AMF) strains, Claroideoglomus claroideum (CC), Claroideoglomus lamellosum (HMC26), and the MIX (CC + HMC26) in yield and phenolic and antioxidant response using chromatographic and spectroscopic methods in potato crops, at increasing levels of water stress, namely, with 100% (0), 70% (S1), and 40% (S2) soil humidity. Two caffeoylquinic acid isomers were detected and their levels showed a tendency to increase under stress together with the AMF inoculation, reaching up to 19.2 mg kg-1 of 5-caffeoylquinic acid and 7.4 mg kg-1 of caffeoylquinic acid isomer when CC was inoculated, and potato plants grew at the highest water starvation condition (S2). Regarding antioxidant activities, a differentiated response was detected depending on the AMF strain, highlighting the effect of HMC26 on Trolox equivalent antioxidant capacity (TEAC) method and CC in cupric reducing antioxidant capacity (CUPRAC) method, reaching up to 1.5 μmol g-1 of TEAC in plants inoculated with HMC26 and 0.9 μmol g-1 of CUPRAC in plants inoculated with CC, both in potato tubers of plants growing under the S2 stress condition. Meanwhile, the use of AMF did not influence the number and biomass of the tubers, but significant changes in the biochemical properties of tubers were observed. The results suggest that specific AMF adaptations to water stress must be considered when inoculation procedures are planned to improve the yield and quality of tubers in potato crops.

Genotypic variation of tomato to AMF inoculation in improving growth, nutrient uptake, yield, and photosynthetic activity

Arbuscular mycorrhizal fungi (AMF) promote water and mineral nutrients uptake by plant roots, which can reduce the chemical fertilizer inputs in crop production. To gain better insight into the comparative effect of different strains of AMF in improving tomato performance at morphological and physiological levels, seedlings of two tomato cultivars (i.e., Better Boy and Roma) were inoculated with four strains of Glomus mosseae (i.e., HS 1–2, BEG 12, BEG 55, and BEG 54) under greenhouse conditions. Results showed that tomato growth and yield varied largely depending on the mycorrhizal strain and tomato cultivar, with wide variations in root colonization ranging from 5.30 to 78.63%. Overall, mycorrhization with BEG 54 showed significantly better tomato performance when compared to the BEG 55, HS 1–2 and BEG 12 strains. In the case of cultivars, Better Boy performed better than Roma cultivar in terms of growth, physiological traits, yield, and fruit quality. The highest plant height, dry matter, nitrogen, phosphorus, potassium, chlorophyll a, chlorophyll b, AMF colonization, yield, fruit juice, ascorbic acid, and titratable acidity contents were recorded in Better Boy cultivar while the highest stem diameter was found in Roma cultivar. Taken together, AMF colonization suggested a promising approach for large-scale tomato production by efficient absorption and utilization of nutrients, and encouraging plants’ symbiotic relationships with soil microorganisms.

Allelopathy and arbuscular mycorrhizal fungi interactions shape plant invasion outcomes

The novel weapon hypothesis suggests that allelopathy is an important mechanism for exotic plants to successfully invade native plant communities. Allelochemicals from exotic plants affect both native plants and arbuscular mycorrhizal fungi (AMF) in soil. To explore these effects, we conducted pot experiments using a native plant community comprising of Chenopodium album L., Vitex negundo L., Rhus chinensis Mill., and Acer truncatum Bunge. We incorporated AMF strains (Funneliformis mosseae, Glomus versiforme, and Rhizophagus intraradices in a 1:1:1 volume ratio) into a soil mixture comprising equal volumes of autoclaved field soil and grass ash at five concentrations (0 g L–1, CK; 10 g L–1, LRE; 20 g L–1, NRE; 30 g L–1, MRE; and 40 g L–1, HRE) to investigate the allelopathy of Rhus typhina L. root and its interactions with AMF on the native plant community. Our results indicated that low concentrations of allelochemicals promoted the relative growth rate and leaf nitrogen content in the native plant community, which was attributed to the increased environmental stress that improved the degree of leaf photosynthetic capacity and organic synthesis rate in the native communities. Moreover, allelochemicals with toxicity decreased the colonization rates of AMF. Meanwhile, the presence of allelopathic effects induced a decrease in leaf nitrogen, and allelopathy altered the effects of AMF on the native community. Specifically, the high concentration of allelochemicals altered the positive effect of AMF on the total aboveground biomass of the native plant community to a negative effect, likely by decreasing colonization rates or affecting soil physicochemical properties and the composition of the mycorrhizal communities. Consequently, it is necessary to consider the effects of AMF when testing the roles of allelopathy or the novel weapons hypothesis in biological invasions. Graphical abstract

Rhizoglomus variabile and Nanoglomus plukenetiae, Native to Peru, Promote Coffee Growth in Western Amazonia.

Coffee (Coffea arabica) is among the world's most economically important crops. Coffee was shown to be highly dependent on arbuscular mycorrhizal fungi (AMF) in traditionally managed coffee plantations in the tropics. The objective of this study was to assess AMF species richness in coffee plantations of four provinces in Perú, to isolate AMF isolates native to these provinces, and to test the effects of selected indigenous AMF strains on coffee growth. AMF species were identified by morphological tools on the genus level, and if possible further to the species level. Two native species, Rhizoglomus variabile and Nanoglomus plukenetiae, recently described from the Peruvian mountain ranges, were successfully cultured in the greenhouse on host plants. In two independent experiments, both species were assessed for their ability to colonize coffee seedlings and improve coffee growth over 135 days. A total of 35 AMF morphospecies were identified from 12 plantations. The two inoculated species effectively colonized coffee roots, which resulted in 3.0-8.6 times higher shoot, root and total biomass, when compared to the non-mycorrhizal controls. R. variabile was superior to N. plukenetiae in all measured parameters, increasing shoot, root, and total biomass dry weight by 4.7, 8.6 and 5.5 times, respectively. The dual inoculation of both species, however, did not further improve plant growth, when compared to single-species inoculations. The colonization of coffee by either R. variabile or N. plukenetiae strongly enhances coffee plant growth. R. variabile, in particular, offers enormous potential for improving coffee establishment and productivity. Assessment of further AMF species, including species from other AMF families should be considered for optimization of coffee growth promotion, both alone and in combination with R. variabile.

Impact of Arbuscular mycorrhizal Fungal Strains Isolated from Soil on the Growth, Yield, and Fruit Quality of Tomato Plants under Different Fertilization Regimens

Arbuscular mycorrhizal fungi (AMF) have emerged as a promising and environmentally friendly solution for sustainable agriculture, offering a reduction in dependence on chemical inputs. The objective of this greenhouse experiment was to assess the efficacy of a natural endomycorrhizal inoculum obtained from leek root fragments, which acted as a trap plant to capture indigenous fungal spores present in the soil of the Guercif region in Morocco. The investigation aimed to comprehensively evaluate the influence of this inoculum on various parameters related to tomato plant growth, yield, and sensory quality. Additionally, different levels of chemical fertilizers, equivalent to 50%, 75%, and 100% of the recommended dosage, were administered in combination with or without the inoculum. The findings elucidated significant advantages associated with mycorrhizal inoculation. The plants subjected to inoculation exhibited increased plant height, augmented leaf and root dry weights, and improved nutrient uptake compared to the control group. Notably, tomato plants treated with 75% of the recommended chemical fertilizer dosage yielded the highest crop production, with no statistically significant difference observed when compared to those receiving the full dosage (100%). Intriguingly, tomato plants grown in substrates receiving 50% chemical fertilizers demonstrated the highest levels of mycorrhization, exhibiting a frequency (F) of 100% and an intensity (M) of 63%. Importantly, the combination of inoculation with a reduced dose of NPK fertilizer (50% of the recommended amount) resulted in significantly elevated concentrations of calcium (Ca), potassium (K), iron (Fe), zinc (Zn), and phosphorus (P) in the plants, attributable to the heightened mycorrhizal colonization of the roots. In terms of fruit characteristics, no significant variations were detected in pH and electrical conductivity (EC) among the treatment groups. However, the inoculated plants exhibited a notable increase in the Brix index, an indicator of sweetness, compared to the control group across all fertilizer doses. Furthermore, inoculation positively influenced the levels of total carotenoids in the fruits. Remarkably, the values of these compounds in the inoculated plants subjected to 50% of the recommended fertilizer dosage surpassed those recorded in the non-inoculated plants receiving the full dosage.

Arbuscular mycorrhizal fungi impact the production of alkannin/shikonin and their derivatives in Alkanna tinctoria Tausch. grown in semi-hydroponic and pot cultivation systems.

Alkanna tinctoria Tausch. is a medicinal plant well-known to produce important therapeutic compounds, such as alkannin/shikonin and their derivatives (A/Sd). It associates with arbuscular mycorrhizal fungi (AMF), which are known, amongst others beneficial effects, to modulate the plant secondary metabolites (SMs) biosynthesis. However, to the best of our knowledge, no study on the effects of AMF strains on the growth and production of A/Sd in A. tinctoria has been reported in the literature. Here, three experiments were conducted. In Experiment 1, plants were associated with the GINCO strain Rhizophagus irregularis MUCL 41833 and, in Experiment 2, with two strains of GINCO (R. irregularis MUCL 41833 and Rhizophagus aggregatus MUCL 49408) and two native strains isolated from wild growing A. tinctoria (R. irregularis and Septoglomus viscosum) and were grown in a semi-hydroponic (S-H) cultivation system. Plants were harvested after 9 and 37 days in Experiment 1 and 9 days in Experiment 2. In Experiment 3, plants were associated with the two native AMF strains and with R. irregularis MUCL 41833 and were grown for 85 days in pots under greenhouse conditions. Quantification and identification of A/Sd were performed by HPLC-PDA and by HPLC-HRMS/MS, respectively. LePGT1, LePGT2, and GHQH genes involved in the A/Sd biosynthesis were analyzed through RT-qPCR. In Experiment 1, no significant differences were noticed in the production of A/Sd. Conversely, in Experiments 2 and 3, plants associated with the native AMF R. irregularis had the highest content of total A/Sd expressed as shikonin equivalent. In Experiment 1, a significantly higher relative expression of both LePGT1 and LePGT2 was observed in plants inoculated with R. irregularis MUCL 41833 compared with control plants after 37 days in the S-H cultivation system. Similarly, a significantly higher relative expression of LePGT2 in plants inoculated with R. irregularis MUCL 41833 was noticed after 9 versus 37 days in the S-H cultivation system. In Experiment 2, a significant lower relative expression of LePGT2 was observed in native AMF R. irregularis inoculated plants compared to the control. Overall, our study showed that the native R. irregularis strain increased A/Sd production in A. tinctoria regardless of the growing system used, further suggesting that the inoculation of native/best performing AMF is a promising method to improve the production of important SMs.

Contribution of Arbuscular Mycorrhizal and Endophytic Fungi to Drought Tolerance in Araucaria araucana Seedlings.

In its natural distribution, Araucaria araucana is a plant species usually exposed to extreme environmental constraints such as wind, volcanism, fires, and low rainfall. This plant is subjected to long periods of drought, accentuated by the current climate emergency, causing plant death, especially in its early growth stages. Understanding the benefits that both arbuscular mycorrhizal fungi (AMF) and endophytic fungi (EF) could provide plants under different water regimes would generate inputs to address the above-mentioned issues. Here, the effect of AMF and EF inoculation (individually and combined) on the morphophysiological variables of A. araucana seedlings subjected to different water regimes was evaluated. Both the AMF and EF inocula were obtained from A. araucana roots growing in natural conditions. The inoculated seedlings were kept for 5 months under standard greenhouse conditions and subsequently subjected to three different irrigation levels for 2 months: 100, 75, and 25% of field capacity (FC). Morphophysiological variables were evaluated over time. Applying AMF and EF + AMF yielded a noticeable survival rate in the most extreme drought conditions (25% FC). Moreover, both the AMF and the EF + AMF treatments promoted an increase in height growth between 6.1 and 16.1%, in the production of aerial biomass between 54.3 and 62.6%, and in root biomass between 42.5 and 65.4%. These treatments also kept the maximum quantum efficiency of PSII (Fv/Fm 0.71 for AMF and 0.64 for EF + AMF) stable, as well as high foliar water content (>60%) and stable CO2 assimilation under drought stress. In addition, the EF + AMF treatment at 25% FC increased the total chlorophyll content. In conclusion, using indigenous strains of AMF, alone or in combination with EF, is a beneficial strategy to produce A. araucana seedlings with an enhanced ability to tolerate prolonged drought periods, which could be of great relevance for the survival of these native species under the current climate change.

Impacts of Tillage Practices on Growth, Phosphorus Uptake, and Yield of Maize in Controlled and Field-Based Studies in Relation to Arbuscular Mycorrhizal Fungi

This study investigated the effects of arbuscular mycorrhizal fungi (AMF) on the growth, phosphorus (P) uptake, and yield of maize in the presence or absence of tillage. The two-year field experiment was conducted in Kanagawa, Japan. Firstly, we investigated whether the presence of indigenous AMF communities in the roots, as determined by amplicon sequencing analysis, contributed to maize growth in Experiment 1, a 2-year field-based study. The findings revealed that the maize (Zea mays L.) in rotary tillage had higher P uptake, growth at the six-leaves collar stage, and yield, compared to no tillage. The AMF communities colonizing maize roots were altered by the presence or absence of tillage; specifically, tillage increased the dominance of the Gigasporaceae, whereas no tillage increased the dominance of the Acaulosporaceae. Based on these findings, we confirmed whether the inoculation of similar AMF strains, as analyzed in the field study of tillage practices on maize roots, produces growth-promoting effects for maize growth in a controlled pot experiment consistent with the results of the field experiment. For experiment 2, Dentiscutata cerradensis TK-1, Cetraspora pellucida SZ-3 (Gigasporaceae), Acaulospora morrowiae AP-5, and A. longula F-1 (Acaulosporaceae) were inoculated as AMF inocula for a pot experiment. The results showed that aboveground biomass did not change with any inoculum compared to the control. The P concentration in maize was higher for D. cerradensis TK-1 and C. pellucida SZ-3 inoculation than for the control. However, inoculation with A. morrowiae AP-5 and A. longula F-1 did not change P concentrations from the control. This indicates that D. cerradensis TK-1 and C. pellucida SZ-3 are more effective in promoting P uptake in maize than in A morrowiae AP-5 and A. longula F-1. Based on field and pot experiments, our findings suggest that tillage practices lead to alterations in the AMF communities that colonize the roots, and this shift may also contribute to changes in P uptake and crop growth.

Engineering Approach for Production of Arbuscular Mycorrhizal Inoculum Adapted to Saline Soil Management

(1) Background: Soil salinity impacts plant growth and productivity in steppic regions. Thus, the current study aims at producing, at low cost, an inoculum composed of native arbuscular mycorrhizal fungi (AMF) strains adapted to saline soil management. (2) Methods: The propagation of the native AMF strains was carried out in three natural saline soils presenting increasing salinity levels (4.5, 8.5 and 9.3 dS·m−1 in Boughzoul (BG), Salt Rocket (SR) and Zaafrane (ZA) sites, respectively). Three host plant species (alfalfa, clover and leek) were tested as trap cultures. AMF spore richness and diversity, the quantification of soil microbial biomass and the determination of the most probable number (MPN) were carried out before and after 24 months culture. Moreover, the mycorrhizal rates of the host plant species were assessed. (3) Results: The moderate saline soil (SR) planted with alfalfa was found to be the most suitable for AMF inoculum production with a maximum of 650 spores, 10 g−1 of soil, a mycorrhizal rate of 86%, 70 propagules·g−1 of soil and the highest microbial biomass content. (4) Conclusion: This study points out the best combination for the production of a more adapted AMF biofertilizer for saline soil management and proposes several indicators for biofertilizer quality evaluation.

The function and community structure of arbuscular mycorrhizal fungi in ecological floating beds used for remediation of Pb contaminated wastewater

Arbuscular mycorrhizal fungi (AMF) have been demonstrated to be ubiquitous in aquatic ecosystems. However, their distributions and ecological functions are rarely studied. To date, a few studies have combined sewage treatment facilities with AMF to improve removal efficiency, but appropriate and highly tolerant AMF strains have not been explored, and the purification mechanisms remain unclear. In this study, three ecological floating-bed (EFB) installations inoculated with different AMF inocula (mine AMF inoculum, commercial AMF inoculum and non-AMF inoculated) were constructed to investigate their removal efficiency for Pb-contaminated wastewater. The AMF community structure shifts in the roots of Canna indica inhabiting EFBs during the three phases (pot culture phase, hydroponic phase and hydroponic phase with Pb stress) were tracked utilizing quantitative real-time polymerase chain reaction and Illumina sequencing techniques. Furthermore, transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) were used to detect the Pb location in mycorrhizal structures. The results showed that AMF could promote host plant growth and enhance the Pb removal efficiency of the EFBs. The higher the AMF abundance, the better the effect of the AMF on Pb purification by EFBs. Both flooding and Pb stress decreased the AMF diversity but did not significantly inhibit the abundance. The three inoculation treatments showed different community compositions with different dominant AMF taxa in different phases, and an uncultured Paraglomus species (Paraglomus sp. LC516188.1) was found to be the most dominant (99.65 %) AMF in the hydroponic phase with Pb stress. The TEM and EDS analysis results showed that the Paraglomus sp. could accumulate Pb in plant roots through their fungal structures (intercellular mycelium, intracellular mycelium, etc.), which alleviated the toxic effect of Pb on plant cells and limited Pb translocation. The new findings provide a theoretical basis for the application of AMF in plant-based bioremediation of wastewater and polluted waterbodies.

Mycorrhization of Xanthosoma sagittifolium L. Schott Plants (White Cultivar): Evaluation of Their Effect on Acid Phosphatase Activity During Growth and Production of Minitubers

This work's main objective was to evaluate the effect of certain strains of arbuscular mycorrhizal fungi on acid phosphatase activity during growth. The treatments applied were, control, Glomus intraradices, Acaulospora tuberculata, Gigaspora margarita, Glomus sp., and the mixture of these four AMF strains. Their effect on the growth of vitroplants was evaluated on days 60, 120, and 180 after inoculation. Mycorrhizal status following treatments and acid phosphatase activity were assessed. The minitubers obtained were subjected to a preservation and germination test. The results showed that the maximum growth peak of X. sagittifolium plants was obtained on day 120 for all treatments. The mixture of the four strains of AMF had more influence on the growth parameters with values of 18.40±0.54 Cm and 42.34±16.67 Cm2, respectively for the average number of roots and leaf area. Mycorrhization did not significantly influence the mean number of leaves and mean plant height. Mycorrhizal structures were observed in all mycorrhizal treatments applied. The frequency of mycorrhization was very high in plants inoculated with Glomus sp. The evaluation of the phosphatase activity shows a significant activity at the level of the leaves with a peak of activity in the plants inoculated with Glomus sp. (47.72±0.07 µM/min/g of FW). Compared to the control, the number of minitubers produced was two to three times higher. The best tuberization percentage (80%) was obtained in plants inoculated with a mixture of AMF strains. The temperature of 7~10°C allowed the preservation of 50% of the germination capacity of the minitubers after two months. Based on the obtained results, it was concluded that fertilization with AMF is beneficial for the stimulation of minitubers production.

Native Arbuscular Mycorrhizal Inoculum Modulates Growth, Oxidative Metabolism and Alleviates Salinity Stresses in Legume Species.

Soil salinity constitutes a major abiotic stress that contributes to soil degradation and crop yield reduction. Using arbuscular mycorrhizal fungi (AMF) inoculation can help to alleviate these deleterious effects. Most researches on AMF application are dealing with ecological restoration, whereas little consideration has been given to agriculture and legume production. The comparison of the efficacy of two AMF inoculums, one native originating from Algerian semiarid saline soils and one commercial inoculum, was carried out regarding their effects on the growth and the mineral nutrition of several legumes species, Medicago sativa, Medicago falcata, Trifolium repens and Trifolium alexandrinum, cultivated in semiarid Algerian saline soil under greenhouse conditions. Our results showed that native mycorrhizal inoculum enhanced shoot biomasses by 20%, mycorrhizal rate by 30%, shoot phosphorus content by 25% and K+/Na+ ratio by 45% for studied plants when compared with commercial inoculum. The best efficiency of the native AMF inoculum is probably due to the complementarity between the AMF strains which composed the inoculum. Funneliformis geosporum was the most abundant species recorded at the end of the experience in all plant roots especially with native inoculum. Our findings pointed out the effectiveness of native AMF inoculum application to promote agricultural production in semiarid saline soils.

Physiological and Metabolic Effects of the Inoculation of Arbuscular Mycorrhizal Fungi in Solanum tuberosum Crops under Water Stress.

Solanum tuberosum is one of the most important crops in the world; however, drought has caused significant losses in its production. One solution is the use of arbuscular mycorrhizal fungi (AMF). In this study, the phenolic profiles and antioxidant activity of the leaves of two potato genotypes (VR808 and CB2011-104) were evaluated over time in crops inoculated with two strains of AMF, as well as a consortium, in combination with a commercial fungicide. In addition, three usable humidity levels were established after the beginning of tuberization. The phenolic compounds found during the first sampling time in the VR808 genotype reached a maximum of 3348 mg kg−1, and in the CB2011-104 genotype, they reached a maximum of 2982 mg kg−1. Seven phenolic compounds were detected in the VR808 genotype, and eleven were detected in the CB2011-104 genotype, reaching the highest concentration at the last sampling time. The antioxidant activity in the first sampling was greater than the Trolox equivalent antioxidant capacity (TEAC), and in the third sampling, the cupric reducing antioxidant capacity (CUPRAC) predominated. The association of AMF with the plant by PCA demonstrated that these fungi assist in protecting the plants against water stress, since in the last harvest, the results were favorable with both mycorrhizae.

Arbuscular Mycorrhizal Fungi Alleviate Salt Stress Damage by Coordinating Nitrogen Utilization in Leaves of Different Species

With the intensification of coastal erosion, damage to coastal shelterbelts has gradually increased. Arbuscular mycorrhizal fungi (AMF) can improve the salinity tolerance and productivity of plants in saline–alkali soils using various strategies including nutrient uptake, osmotic regulation, soil shaping, etc. Thus, the application of AMF to alleviate the impacts of salinization for these shelterbelts has become a research hotspot. For this study, we investigated the effects of inoculation with different AMF strains on the growth and nitrogen (N) utilization of Gleditsia sinensis Lam. and Zelkova serrata (Thunb.) Makino leaves under different salt concentrations. As the salt concentration increased, the growth rates and leaf areas of the autoclaved AMF inoculant (CK) treatment exhibited a decreasing trend for both G. sinensis and Z. serrata, while Funneliformis mosseae (FM) and Corymbiglomus tortuosum (CT) treatments weakened this trend. Between them, on average, FM increased the G. sinensis height growth rate by 396.9%, ground diameter growth rate by 99.0%, and Z. serrata leaf area by 29.1%. At a salt concentration of 150 mM, the chlorophyll content and nitrate reductase activities of leaves under the FM treatment for both tree species were significantly higher than for CK, with an average increase in chlorophyll content of 106.1% and nitrate reductase activities by 74.6%. Moreover, the AMF inoculation significantly reduced the leaf N content and photosynthetic N-use efficiency of G. sinensis in contrast to Z. serrata. Further, in contrast to G. sinensis, the photosynthetic N-use efficiency was significantly positively correlated with the growth rate and leaf area of Z. serrata. Meanwhile, the nitrate reductase activity contributed most to the growth rate and leaf area of Z. serrata. Our results suggest that the issues with coastal shelterbelts might be effectively alleviated through appropriate AMF–plant combinations, which is of great significance for the optimization of forestry production.

Arbuscular Mycorrhizal Fungal Inoculation Increases Organic Selenium Accumulation in Soybean (Glycine max (Linn.) Merr.) Growing in Selenite-Spiked Soils.

Selenium (Se) is an essential trace element for humans. Arbuscular mycorrhizal fungi (AMF) play a crucial role in increasing plant micronutrient acquisition. Soybean (Glycine max (Linn.) Merr.) is a staple food for most people around the world and a source of Se. Therefore, it is necessary to study the mechanism of Se intake in soybean under the influence of AMF. In this study, the effects of fertilization with selenite and inoculation with different AMF strains (Claroideoglomus etunicatum (Ce), Funneliformis mosseae (Fm)) on the accumulation and speciation of Se in common soybean plants were discussed. We carried out a pot experiment at the soil for 90 days to investigate the impact of fertilization with selenite and inoculation with Ce and Fm on the Se fractions in soil, soybean biomass, accumulation and speciation of Se in common soybean plants. The daily dietary intake of the Se (DDI) formula was used to estimate the risk threshold of human intake of Se from soybean seeds. The results showed that combined use of both AMF and Se fertilizer could boost total Se and organic Se amounts in soyabean seeds than that of single Se application and that it could increase the proportion of available Se in soil. Soybean inoculated with Fm and grown in soil fertilized with selenite had the highest organic Se. The results suggest that AMF inoculation could promote root growth, more soil water-soluble Se and higher Se uptake. The maximum Se intake of soybean for adults was 93.15 μg/d when treated with Se fertilizer and Fm, which satisfies the needs of Se intake recommended by the WHO. Combined use of AMF inoculation and Se fertilizer increases the bioavailable Se in soil and promotes the total Se concentration and organic Se accumulation in soybean. In conclusion, AMF inoculation combined with Se fertilization can be a promising strategy for Se biofortification in soybean.