Arbuscular Mycorrhizal Fungi Isolates Research Articles

Leveraging the complex interplay between arbuscular mycorrhizal fungi, seasonal dynamics, and genotypic diversity to optimize maize productivity in semi-arid agroecosystems

Maize production under low-input agricultural systems in semi-arid areas of Sub-Saharan Africa faces significant challenges, primarily stemming from the synergistic impacts of climate variability and suboptimal agronomic practices. Harnessing soil microbiota, particularly arbuscular mycorrhizal fungi (AMF), represents a pivotal strategy for bolstering low-input systems. However, their functional utility is contingent upon their compatibility with the prevailing environmental conditions and biotic interactions. This study examines the influence of two distinct AMF inoculants on the growth and yield attributes of diverse maize genotypes across varying seasons within semi-arid regions of Kenya. We hypothesized that AMF inoculants exhibit differential adaptability to varying environmental sites and seasons, and their interaction will enhance the provision of key ecosystem services important for maize production. Field experiments were conducted in three semi-arid Counties (Tharaka-Nithi, Embu, and Kitui) during the 2019/2020 cropping seasons. A randomized complete block design with three replications and three treatments was adopted. Treatments consisted of Rhizatech (a commercial AMF inoculant), a consortium of AMF isolates (Rhizophagus irregularis and Funneliformis mosseae), and a non-inoculated control. In season one, notable interaction effects were observed for both site × maize genotype (p = 0.0007) and site × AMF inoculation (p < 0.0001), whereby Duma 43 genotype had the highest yield in Embu (11.93 t ha−1) and Kitui (11.76 t ha−1) counties, and Rhizatech and consortium inoculation consistently led to elevated grain yields across all three genotypes in Kitui, surpassing non-inoculated controls. AMF inoculation notably augmented phosphorus (P) uptake, with Rhizatech demonstrating a 79.7 % increase and consortium showing a 38.7 % increase in shoot P content compared to control plants in season 1. These findings highlight the complex interplay between AMF effectiveness, seasonal variations, and maize diversity. Further research is needed to elucidate the underlying mechanisms driving these seasonal shifts, allowing for optimized AMF inoculation strategies for improved maize performance under diverse conditions.

Divergent colonization traits, convergent benefits: different species of arbuscular mycorrhizal fungi alleviate Meloidogyne incognita damage in tomato

Arbuscular mycorrhizal fungi (AMF) can increase plant tolerance and/or resistance to pests such as the root-knot nematode Meloidogyne incognita. However, the ameliorative effects may depend on AMF species. The aim of this work was therefore to evaluate whether four AMF species differentially affect plant performance in response to M. incognita infection. Tomato plants grown in greenhouse conditions were inoculated with four different AMF isolates (Claroideoglomus claroideum, Funneliformis mosseae, Gigaspora margarita, and Rhizophagus intraradices) and infected with 100 second stage juveniles of M. incognita at two different times: simultaneously or 2 weeks after the inoculation with AMF. After 60 days, the number of galls, egg masses, and reproduction factor of the nematodes were assessed along with plant biomass, phosphorus (P), and nitrogen concentrations in roots and shoots and root colonization by AMF. Only the simultaneous nematode inoculation without AMF caused a large reduction in plant shoot biomass, while all AMF species were able to ameliorate this effect and improve plant P uptake. The AMF isolates responded differently to the interaction with nematodes, either increasing the frequency of vesicles (C. claroideum) or reducing the number of arbuscules (F. mosseae and Gi. margarita). AMF inoculation did not decrease galls; however, it reduced the number of egg masses per gall in nematode simultaneous inoculation, except for C. claroideum. This work shows the importance of biotic stress alleviation associated with an improvement in P uptake and mediated by four different AMF species, irrespective of their fungal root colonization levels and specific interactions with the parasite.

Synergic effect of Arbuscular mycorrhizal fungi and potassium fertilizer improves biomass-related characteristics of cocoa seedlings to enhance their drought resilience and field survival

Abstract Drought is the most widespread threat to cocoa production. We assessed the combined effect of arbuscular mycorrhizal fungi (AMF) and potassium fertilizer on cocoa drought resilience and survival at the nursery to 2 years after transplanting to field. Nursery and field experiments were conducted at the FRNR farm (6°43N and 1°36W), Ghana, from 2020 to 2022. A 3 × 3 × 2 factorial experiment in a RCBD with three varieties of cocoa (CRG8914 × \times PA150; AMAZ315–15 × \times EQX78; PA150 × \times CRG 0314: V1; V2; V3 respectively), potassium (0, 2, and 4 g/plant), and mycorrhizal spore treatment (non-AMF and AMF inoculated) was used. Soil from the cocoa rhizosphere was collected and the wet sieving, decantation, and sucrose centrifugation techniques were used for the isolation of AMF. Rhizophagus irregularis was identified using the morphological method. The identified inoculum was prepared using the trap culture technique. K levels with AMF recorded the highest plant height (50.27 cm) than the non-AMF seedlings (41.4 cm). 2 g K × AMF in V1 and V2 had the highest (p &lt; 0.05) above-ground (5.13 g) and below-ground (2.81 g) biomass, respectively. At 24 months, V1 × 0 g and V3 × 4 g without AMF had mortality of 60% and 50%, respectively, while V1 × 4 g and V2 × 2 g with AMF had 2% mortality rate. In conclusion, this has implications for cocoa nutrient management, yield, and climate-smart strategies for the attainment of Sustainable Development Goal 13 (climate Action).

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.

Distinct impact of arbuscular mycorrhizal isolates on tomato plant tolerance to drought combined with chronic and acute heat stress

Arbuscular mycorrhizal (AM) fungi could mitigate individual drought and heat stress in host plants. However, there are still major gaps in our understanding of AM symbiosis response to the combined stresses. Here, we compared seven AM fungi, Rhizophagus irregularis, Funneliformis mosseae, Funneliformis geosporum, Funneliformis verruculosum, Funneliformis coronatum, Septoglomus deserticola, Septoglomus constrictum, distributed to many world regions in terms of their impacts on tomato endurance to combined drought and chronic heat as well as combined drought and heat shock. A multidisciplinary approach including morphometric, ecophysiological, biochemical, targeted metabolic (by ultrahigh-performance LC-MS), and molecular analyses was applied. The variation among AM fungi isolates in the enhancement in leaf water potential, stomatal conductance, photosynthetic activity, and maximal PSII photochemical efficiency, proline accumulation, antioxidant enzymes (POD, SOD, CAT), and lowered ROS markers (H2O2, MDA) in host plants under combined stresses were observed. S. constrictum inoculation could better enhanced the host plant physiology and biochemical parameters, while F. geosporum colonization less positively influenced the host plants than other treatments under both combined stresses. F. mosseae- and S. constrictum-associated plants showed the common AM-induced modifications and AM species-specific alterations in phytohormones (ABA, SA, JA, IAA), aquaporin (SlSIP1-2; SlTIP2-3; SlNIP2-1; SlPIP2-1) and abiotic stress-responsive genes (SlAREB1, SlLEA, SlHSP70, SlHSP90) in host plants under combined stresses. Altogether, mycorrhizal mitigation of the negative impacts of drought + prolonged heat and drought + acute heat, with the variation among different AM fungi isolates, depending on the specific combined stress and stress duration.

Effects of Arbuscular Mycorrhizal Fungi on Robinia pseudoacacia L. Growing on Soils Contaminated with Heavy Metals.

Arbuscular mycorrhizal fungi (AMF) have been shown to assist plants in increasing metal tolerance and accumulation in heavy metal (HM)-contaminated soils. Herein, a greenhouse pot experiment was conducted to assess the interactions of growth substrates (S1, S2, and S3, respectively) with various HM contamination and nutrient status sampling from a typical contaminated soil and tailings in Shuikoushan lead/zinc mining in Hunan province, China, and AMF inoculation obtained from plants in uncontaminated areas (Glomus mosseae, Glomus intraradices, and uninoculated, respectively) on the biomass and uptake of HMs and phosphorus (P) by the black locust plant (Robinia pseudoacacia L.). The results indicated that the inoculation with AMF significantly enhanced the mycorrhizal colonization of plant roots compared with the uninoculated treatments, and the colonization rates were found to be higher in S1 and S2 compared with S3, which were characterized with a higher nutrient availability and lead concentration. The biomass and heights of R. pseudoacacia were significantly increased by AMF inoculation in S1 and S2. Furthermore, AMF significantly increased the HM concentrations of the roots in S1 and S2 but decreased the HM concentrations in S3. Shoot HM concentrations varied in response to different AMF species and substrate types. Mycorrhizal colonization was found to be highly correlated with plant P concentrations and biomass in S1 and S2, but not in S3. Moreover, plant biomass was also significantly correlated with plant P concentrations in S1 and S2. Overall, these findings demonstrate the interactions of AMF inoculation and growth substrates on the phytoremediation potential of R. pseudoacacia and highlights the need to select optimal AMF isolates for their use in specific substrates for the remediation of HM-contaminated soil.

Indigenous and commercial isolates of arbuscular mycorrhizal fungi display differential effects in Pyrus betulaefolia roots and elicit divergent transcriptomic and metabolomic responses.

Arbuscular mycorrhizal fungi (AMF) are beneficial soil fungi which can effectively help plants with acquisition of mineral nutrients and water and promote their growth and development. The effects of indigenous and commercial isolates of arbuscular mycorrhizal fungi on pear (Pyrus betulaefolia) trees, however, remains unclear. Trifolium repens was used to propagate indigenous AMF to simulate spore propagation in natural soils in three ways: 1. the collected soil was mixed with fine roots (R), 2. fine roots were removed from the collected soil (S), and 3. the collected soil was sterilized with 50 kGy 60Co γ-radiation (CK). To study the effects of indigenous AMF on root growth and metabolism of pear trees, CK (sterilized soil from CK in T. repens mixed with sterilized standard soil), indigenous AMF (R, soil from R in T. repens mixed with sterilized standard soil; S, soil from S in T. repens mixed with sterilized standard soil), and two commercial AMF isolates (Rhizophagus intraradices(Ri) and Funneliformis mosseae (Fm)) inoculated in the media with pear roots. Effects on plant growth, root morphology, mineral nutrient accumulation, metabolite composition and abundance, and gene expression were analyzed. AMF treatment significantly increased growth performance, and altered root morphology and mineral nutrient accumulation in this study, with the S treatment displaying overall better performance. In addition, indigenous AMF and commercial AMF isolates displayed common and divergent responses on metabolite and gene expression in pear roots. Compared with CK, most types of flavones, isoflavones, and carbohydrates decreased in the AMF treatment, whereas most types of fatty acids, amino acids, glycerolipids, and glycerophospholipids increased in response to the AMF treatments. Further, the relative abundance of amino acids, flavonoids and carbohydrates displayed different trends between indigenous and commercial AMF isolates. The Fm and S treatments altered gene expression in relation to root metabolism resulting in enriched fructose and mannose metabolism (ko00051), fatty acid biosynthesis (ko00061) and flavonoid biosynthesis (ko00941). This study demonstrates that indigenous AMF and commercial AMF isolates elicited different effects in pear plants through divergent responses from gene transcription to metabolite accumulation.

Importance and roles of arbuscular mycorrhizal fungi in new Caledonian ultramafic soils

ABSTRACT Our knowledge about New Caledonian serpentine ecosystems has increased greatly during the past half-century, mainly thanks to Jaffré’s group. However, research on soil microflora and plant symbionts started only in the nineties and was mainly published during the last two decades. We aim to synthesize these studies, focusing particularly on arbuscular mycorrhizal fungi (AMF). Research on AMF consists firstly of a global and inventory approach aiming to produce a basic but essential lacking knowledge. These studies showed that AMF are abundant in ultramafic soils and concerned nearly all plant species of these ecosystems. Even Ni-hyperaccumulator plants and sedges, generally considered non-mycorrhizal, were found to be functionally colonized by AMF in New Caledonian ultramafic soils. The adaptation of AMF communities to the extreme conditions of these soils led to high levels of metal tolerance (particularly to Ni) and noticeable originality of the taxa. The influence of these symbionts on plant growth and adaptation was assessed in greenhouse and field conditions. An accurate selection of AMF isolates that improve plant growth, and plant metal tolerance was performed. It was demonstrated that combinations of AMF isolates with complementary functional traits showed highly synergistic effects on plant development. Finally, a partnership with a biotechnological company led to the production of an efficient commercial inoculant now used in the ecological restoration of mine-degraded areas. Today studies are focused mainly on the additive effects of AMF and mycorrhiza-helper bacteria.

Brassicaceae, Chenopodiaceae ve Urticaceae Familyalarına Ait Bazı Bitki Türlerinin Arbusküler Mikorhizal Fungus (AMF) ve Rhizobacteria Arasındaki İlişki

This study was conducted to investigate the effects of some plant growth-promoting rhizobacteria (PGPR) on the arbuscular mycorrhizal fungi (AMF) formation on [Brassica oleracea (cauliflower), Spinacia oleracea (spinach) ,and Urtica urens (stinging nettle)] belonging to Brassicaceae, Chenopodiaceae and Urticaceae families, which are known to have a negative influence on the symbiotic life formation with AMF. Two PGPR isolates that contributed to the plant's growth and served as a “mycorrhizal helper” in various hosts were predetermined at the initial stage; then they were applied to three plant species with AMF species [Gigaspora margarita and commercial AMF (ERS)]. The obtained results revealed that combined AMF x PGPR treatments improved the growth and morphological development parameters of cauliflower, spinach, and nettle plants. PGPR bacteria had different effects on AMF root colonization depending on the plant species. The highest root colonization rate was achieved in spinach plants with the commercial AMF treatments. Commercial AMF isolate, alone or in combination with PGPR strains, was also found to increase AMF spore density and mycorrhizal dependency in cauliflower and spinach plants. There was no significant difference in total phosphorus content in cauliflower and nettle compared to the control group, and only one application group (G. margarita x PGPR) in spinach plants had an increase in phosphorus content.

Arbuscular mycorrhizal fungi communities shaped by host‐plant affect the outcome of plant–soil feedback in dryland restoration

Abstract Plant inoculation with arbuscular mycorrhizal fungi (AMF) can be a useful tool to overcome challenges in dry forest restoration. However, advances are still needed to guide choices regarding soil origin and inoculum production methods, since outcomes can vary due to plant–soil feedbacks (PSF). We evaluate how soil origin and host plant used for inoculum production affect AMF community and therefore the plant biomass accumulation and functional traits. In the conditioning phase, we investigated whether soils originating from a recovered area (Quarry) and a vegetation fragment (Caatinga) would have their AMF communities modified due to the growth of Sorghum bicolor (used for inoculum production) and Senna uniflora (used in Brazilian semiarid restoration). In the feedback phase, we compared the performance of four plants species growing on a degraded soil and inoculated or not by a mixture of AMF isolates in comparison to soil inoculum prepared from the conditioning phase. The inoculum from Caatinga presented seven times more AMF species compared to that from the Quarry, which presented ruderal and stress tolerant species. The soil inoculum conditioned by S. uniflora, regardless of origin, presented greater evenness compared to the soil inoculum produced with S. bicolor and promoted 33% more plant biomass compared to the control without inoculation. Root colonization by AMF increased PSF and decreased plant investment in functional traits such as specific root length (SRL) and specific leaf area (SLA). Our results demonstrate the importance of adopting strategies that preserve local adaptation of inoculants produced. The use of native plant for propagation of native AMF in the conditioning phase provided more positive responses for Mesosphaerum suaveolens and Rhaphiodon echinus than inoculated with introduced AMF isolates. This is probably due to the interaction of inoculated plants with responsive AMF present in the soil. Synthesis and applications. Our study shows that conditioning field‐collected soil with Senna uniflora and using it for inoculation can be a simple technique to promote biomass accumulation for other native herbaceous species. This preserves the compatibility between the soil inoculum produced with native AMF and native plants, representing an important tool for restoration programs.

Arbuscular Mycorrhizal Fungi Improve Growth and Phosphate Nutrition of Acacia seyal (Delile) under Saline Conditions

Many plant species adapted to semi-arid environments are grown in the Sahelian region in northern Africa. One such species is Acacia seyal (Delile), a multipurpose leguminous tree grown in various agroecological zones, including saline soils. These challenging arid and semi-arid environments harbor a diversity of arbuscular mycorrhizal fungi (AMF) communities that can develop symbiotic associations with plants to improve their hydromineral nutrition. This study compared the effects of native AMF communities isolated from semi-arid sites (high, moderate, and low salinity zones Ndiafate, Ngane, and Bambey, respectively) and the AMF Rhizoglomus aggregatum on the development and phosphate nutrition of A. seyal seedlings subject to three salinity treatments (0, 340, and 680 mM). Plant height, dry matter weight of the shoots and roots, and phosphorus uptake from the soil were measured. Plants inoculated with AMF native species from each site that were provided with up to 340 mM of NaCl had greater shoot height than plants grown under 680 mM salinity. At NaCl concentrations above 340 mM, shoot and root development of A. seyal seedlings diminished. However, dry matter production of shoots (7%) and roots (15%) improved following AMF inoculation compared with the control (respectively 0.020 and 0.07 g for shoots and roots). When inoculated with AMF isolates from the high salinity zone (Ndiafate), phosphate content/nutrition was increased by 10% around 30 days after inoculation compared with non-inoculated seedlings (2.84 mg/kg of substrate). These results demonstrate that native AMF inoculants are capable of helping plants withstand environmental constraints, especially those exposing plants to harsh climatic conditions. We discuss insights on how AMF influences the interplay between soil phosphorus and perceived salinity that may have implications for broader relationships between plants and symbiotic fungi.

Growth Responses of Three European Weeds on Different AMF Species during Early Development.

Arbuscular mycorrhizal fungi (AMF) have multiple functions in agroecosystems and affect many processes below- and aboveground, including plant productivity. Mycorrhizal symbiosis is not necessarily beneficial for the host plant and the growth response can be not only positive but also neutral or negative. Among other factors, the responsiveness of plants to AMF depends on the plant-fungus combination. To find out whether the AMF species or isolate is a decisive factor for growth responses of weeds, 44 AMF isolates were tested in a pot experiment for their effects on three agricultural weeds: Echinochloa crus-galli, Solanum nigrum and Papaver rhoeas. The 44 isolates cover 18 AMF species from 13 genera and all 5 orders of the Glomeromycota. The aboveground biomass of the weeds was determined after different times of growth of each weed. In most cases, the effects of AMF isolates on weed growth were negative or neutral. We conclude that some weed species do not benefit from AMF in terms of growth. AMF species can even cause negative growth responses, an effect that may be of practical interest for organic farming where the aim is to obtain a high diversity and concentration of native AMF for the benefit of the cultivated crops without increasing the labor for mechanical weeding.

Two isolates of Rhizophagus irregularis select different strategies for improving plants phosphorus uptake at moderate soil P availability

The roots of most terrestrial plants form symbioses with a diversity of arbuscular mycorrhizal (AM) fungi, which make substantial contributions to plant phosphorus (P) uptake. Large genetic variation exists within AM fungi of the same species. However, the impact of these variations, on the mycorrhizal contribution to plants' P uptake by different isolates of the same species and the differences in physiological mechanism remain unknown. In the present study, we selected maize (genotype Oh 43) as the host plant and investigated the response of plant P uptake and soil organic P use efficiency to two different AM fungal isolates, Rhizophagus irregularis MUCL 41833 and R. irregularis MUCL 43194 at three soil P availability levels (10.3, 18.6, 43.3 mg kg−1, representing low, medium and high soil available P level, respectively). We found that at the medium soil available P level, R. irregularis MUCL 41833 produced large amounts of extraradical hyphae to explore soil and induced greater expression of phosphate transporter gene ZmPHT1;6 involved in the mycorrhizal pathway. While, R. irregularis MUCL 43194 recruited a specific, and different, bacterial community in the rhizosphere compared to R. irregularis MUCL 41833. This shift in rhizosphere microbiome was characterized by the recruitment of a greater abundance of Betaproteobacteriales when the plant was colonized by R. irregularis MUCL 43194, which showed a strong positive correlation with alkaline phosphatase activity, and suggested a link to greater organic P mineralization. Collectively, our results suggest that the two isolates of R. irregularis have different strategies for improving plant P uptake at the medium soil available P level, which deepened our understanding on the contribution and complexity of the mycorrhizal pathway to plant P uptake.

The Effect of Arbuscular Mycorrhizal Fungi and Azotobacter on the Growth of Toona sureni Merr (Suren) Seedlings on Post-Coal Mining Land

. This research aimed to investigate the growth of Toona sureni Merr (suren) seedlings inoculated with arbuscular mycorrhizal fungi (AMF) and azotobacter on land previously used for coal mining. We also investigated the source of AMF and azotobacter isolates, resulting in the best growth of suren seedlings on the post-coal mining land. We used a completely randomized design in a factorial manner with two treatment factors. The first factor was the inoculation of AMF isolates (C), which consisted of 5 levels, namely: without AMF (C0), AMF from the suren rhizosphere (C1), AMF from Gmelina arborea (gmelina) rhizosphere (C2), AMF from Durio zibethinus (durian) rhizosphere (C3), and AMF from Acacia mangium (acacia) rhizosphere (C4). The second factor was the inoculation of azotobacter isolates (A), which consisted of 4 levels, namely: without azotobacter (A0), azotobacter from the suren rhizosphere (A1), azotobacter from the gmelina rhizosphere (A3), and azotobacter from the durian rhizosphere (A4). Each treatment had six replications. Data analysis used ANOVA at a 5% test level. Then, we used the orthogonal contrast test to compare the growth of the inoculated seedlings with AMF and azotobacter with that of the un-inoculated seedlings. Meanwhile, to find out the source of isolates for AMF and azotobacter, which resulted in the best growth of the seedlings, we analyzed them with a two-way Duncan Multiple Range Test (DMRT). The results of the ANOVA showed that the AMF inoculation had a significant difference in height growth, diameter growth, and growth in the number of leaves. In contrast, azotobacter inoculation had no significant difference in the same growth variables. The interaction between AMF inoculation and Azotobacter was not significantly different in height growth but in diameter and leaf number growth. The DMRT analysis showed that AMF from suren rhizosphere isolates resulted in the best growth of the suren seedlings.

Multiple Arbuscular Mycorrhizal Fungal Consortia Enhance Yield and Fatty Acids of Medicago sativa: A Two-Year Field Study on Agronomic Traits and Tracing of Fungal Persistence.

Arbuscular mycorrhizal fungi are promoted as biofertilizers due to potential benefits in crop productivity, and macro- and microelement uptake. However, crop response to arbuscular mycorrhizal fungi (AMF) inoculation is context-dependent, and AMF diversity and field establishment and persistence of inoculants can greatly contribute to variation in outcomes. This study was designed to test the hypotheses that multiple and local AMF inoculants could enhance alfalfa yield and fatty acids (FA) compared to exotic isolates either single or in the mixture. We aimed also to verify the persistence of inoculated AMF, and which component of the AMF communities was the major driver of plant traits. Therefore, a field experiment of AMF inoculation of alfalfa (Medicago sativa L.) with three single foreign isolates, a mixture of the foreign isolates (FMix), and a highly diverse mixture of local AMF (LMix) was set up. We showed that AMF improved alfalfa yield (+ 68%), nutrient (+ 147% N content and + 182% P content in forage), and FA content (+ 105%). These positive effects persisted for at least 2 years post-inoculation and were associated with enhanced AMF abundance in roots. Consortia of AMF strains acted in synergy, and the mixture of foreign AMF isolates provided greater benefits compared to local consortia (+ 20% forage yield, + 36% forage N content, + 18% forage P content, + 20% total FA in forage). Foreign strains of Funneliformis mosseae and Rhizophagus irregularis persisted in the roots of alfalfa 2 years following inoculation, either as single inoculum or as a component of the mixture. Among inoculants, F. mosseae BEG12 and AZ225C and the FMix exerted a higher impact on the local AMF community compared with LMix and R. irregularis BEG141. Finally, the stimulation of the proliferation of a single-taxa (R. irregularis cluster1) induced by all inoculants was the main determinant of the host benefits. Crop productivity and quality as well as field persistence of inoculated AMF support the use of mixtures of foreign AMF. On the other hand, local mixtures showed a lower impact on native AMF. These results pave the way for extending the study on the effect of AMF mixtures for the production of high-quality forage for the animal diet.

Does Commercial Inoculation Promote Arbuscular Mycorrhizal Fungi Invasion?

Interventions with commercial inoculants have the potential to reduce the environmental footprint of agriculture, but their indiscriminate deployment has raised questions on the unintended consequences of microbial invasion. In the absence of explicit empirical reports on arbuscular mycorrhizal fungi (AMF) invasion, we examine the present framework used to define AMF invasion and offer perspectives on the steps needed to avoid the negative impacts of AMF invasion. Although commercial AMF isolates are potential invaders, invasions do not always constitute negative impacts on native community diversity and functions. Instead, the fates of the invading and resident communities are determined by ecological processes such as selection, drift, dispersal, and speciation. Nevertheless, we recommend strategies that reduce overdependence on introduced inoculants, such as adoption management practices that promote the diversity and richness of indigenous AMF communities, and the development of native propagules as a supplement to commercial AMF in applicable areas. Policies and regulations that monitor inoculant value chains from production to application must be put in place to check inoculant quality and composition, as well as the transport of inoculants between geographically distant regions.

Arbuscular Mycorrhizal Fungal Diversity Associated with Olea europaea L. Growing in Yunnan Province, Southwestern China

Olive (Olea europaea L.) is one of the most important and widely cultivated fruit trees, with high economic, ecological, cultural and scientific value. China began introducing and cultivating olive in the 1960s, and Yunnan Province is one of the main growing areas. Improving the cultivation and productivity of this tree crop species is an important challenge. Olive is a typical mycotrophic species and the potential of arbuscular mycorrhizal fungi (AMF) for this plant is well recognized; nevertheless, studies of olive AMF in China are still very limited. Roots and rhizosphere soils of olive were sampled from five representative growing sites in the Yunnan Province of China to investigate the AMF colonization status in the root systems, the AMF community in the olive orchards and the edaphic factors influencing the arbuscular mycorrhizal (AM) parameters. Root samples of olive trees from different growing sites generally showed AMF colonization, suggesting that autochthonous AMF manifest a high efficiency in colonizing the roots of olive plants. The spore density on the five sites ranged from 81.6 to 350 spores per 20 g soil. Twenty-three AMF species from 9 genera were identified in total, and Glomeraceae was the dominant family. The findings of our study suggested a high AMF diversity harbored by olive growing in different areas of the Yunnan Province, Southwestern China. Furthermore, the hyphal colonization in roots positively correlated with soil pH and EC. The arbuscule colonization in olive roots negatively correlated with soil pH, EC, OM, TN, TP and AN. The spore density positively correlated with OM, TN, AN, AP and sand content. Finally, the Shannon index of AMF in the rhizosphere soil positively correlated with the clay content, but negatively correlated with soil pH, TN and silt content. The high diversity of autochthonous AMF in Yunnan is promising for screening AMF isolates for utilization in the efficient cultivation of this crop.

Application of Native or Exotic Arbuscular Mycorrhizal Fungi Complexes and Monospecific Isolates from Saline Semi-Arid Mediterranean Ecosystems Improved Phoenix dactylifera’s Growth and Mitigated Salt Stress Negative Effects

The date, the palm tree (Phoenix dactylifera L.) is an important component of arid and semi-arid Mediterranean ecosystems, particularly in Morocco where it plays a considerable socio-economic and ecological role. This species is largely affected by desertification, global warming, and anthropic pressure. Salinity is a very worrying problem that negatively affects the growth and the physiological and biochemical activities of the date palm. In these arid zones, the main challenge is to develop new environmentally friendly technologies that improve crop tolerance to abiotic restraints including salinity. In this sense, Arbuscular mycorrhizal fungi (AMF) have received much attention due to their capability in promoting plant growth and tolerance to abiotic and biotic stresses. It is thus fitting that the current research work was undertaken to evaluate and compare the effects of native AMF on the development of the growth and tolerance of date palm to salt stress along with testing their role as biofertilizers. To achieve this goal, two complexes and two monospecific isolates of native and non-native AMF were used to inoculate date palm seedlings under saline stress (0 g·L−1 Na Cl, 10 g·L−1, and 20 g·L−1 Na Cl). The obtained results showed that salinity drastically affected the physiological parameters and growth of date palm seedlings, whilst the application of selected AMF significantly improved growth parameters and promoted the activities of antioxidant enzymes as a protective strategy. Inoculation with non-native AMF complex and monospecific isolates showed higher responses for all analyzed parameters when compared with the native complex and isolate. It therefore becomes necessary to glamorize the fungal communities associated with date palm for their use in the inoculation of Phoenix dactylifera L. seedlings.

Morphological and molecular identifications of three native arbuscular mycorrhizal fungi isolated from the rhizosphere of Elaeis guineensis and Jatropha curcas in Indonesia

Abstract. Rini MV, Yelli F, Tambunan DL, Damayanti I. 2021. Morphological and molecular identifications of three native arbuscular mycorrhizal fungi isolated from the rhizosphere of Elaeis guineensis and Jatropha curcas in Indonesia. Biodiversitas 22: 4940-4947. Molecular analysis has been widely used to provide more accurate identification within arbuscular mycorrhizal fungi (AMF) species than identification based on morphology. However, morphological analysis is essential for a basic preliminary of classification studies. Therefore, a study is needed to complete the identification of AMF isolates through morphological and molecular analyses. This research used three AMF isolates, namely MV 5, MV 17, and MV 18, which were isolated from Indonesian agricultural land. Spore-based taxonomy (shape, size, color, ornamentation, PVLG, and Melzer’s reaction) and fungal colonization on roots of maize trap plants were employed for the morphological studies. AMF species identification was performed using molecular analysis through nested-Polymerase Chain Reaction (PCR) to amplify a fragment of SSU rRNA followed by sequencing and phylogenetic tree construction. Morphological analysis showed that MV 5 had spores borne from the neck of the sporiferous saccule, MV 17 was found to have a bulbous suspensor without a germination shield, and MV 18 had spores borne from subtending hyphae. The SSUR rRNA analysis revealed that MV 5, MV 15, and MV 18 were identified as Acaulospora longula, Gigaspora margarita, and Glomus etunicatum, respectively. Both morphological and molecular methods demonstrated reliable and consistent results that complement AMF taxonomy studies.

Mycorrhizal growth and phosphorus responses of tropical soybean (Glycine max L.) cultivars differ with arbuscular mycorrhizal fungi isolates and phosphorus application rates in a derived-savanna zone of Nigeria

Arbuscular mycorrhizal fungi (AMF) form symbiosis with most crops and provide a sustainable approach to promote crop productivity in phosphorus (P) deficient soils. There is scarcity of information on mycorrhizal growth and P responses in relation to different AMF isolates, P rates and soybean cultivars in Nigeria. Thus, field experiments were conducted for two consecutive years (2017 − 2018) to explore the impacts of different AMF isolates (Funneliformis mosseae, Rhizophagus intraradices and Claroideoglomus etunicatum) and P application rates (0, 20 and 40 kg P2O5 ha−1) on plant growth, mycorrhizal responses, nodulation, P nutrition and grain yield of two soybean cultivars (TGx 1448-2E and TGX 1440-1E). The results showed that mycorrhizal inoculation significantly enhanced root colonization, shoot biomass, nodulation, P uptake, P use efficiency and grain yield of the soybean cultivars compared to control. Inoculation of R. intraradices and F. mosseae consistently favored mycorrhizal responses compared to C. etunicatum. Application of high P rate (40 kg ha−1) negatively affected root colonization, mycorrhizal growth and P responses in inoculated plants. Both cultivars showed similar mycorrhizal responses. Mycorrhizal growth and P responses were significantly enhanced with inoculation of R. intraradices or F. mosseae and P rate of 20 kg ha−1, which resulted in increased P uptake, shoot biomass and grain yield in both cropping years . The findings indicated that inoculation of R. intraradices or F. mosseae with moderate P rate (20 kg ha−1) is optimal to promote plant growth, P nutrition and grain yield of tropical soybean for sustainable cultivation in Nigeria.