Arbuscular Mycorrhizal Fungi Community Composition Research Articles

Impact of Silver Nanoparticles on Arbuscular Mycorrhizal Fungi and Glomalin-Related Soil Proteins in the Rhizosphere of Maize Seedlings

Glomalin-related soil protein (GRSP), an important arbuscular mycorrhizal (AM) fungal by-product, plays a key role in preserving or sequestrating soil organic carbon (C). Silver nanoparticles (AgNPs) have become an emerging contaminant and their impacts on soil ecosystems attract increasing concerns. The dynamics of AM fungi and GRSP could therefore form the basis for an in-depth exploration of the influences of AgNPs on soil ecosystems. This study investigated the effects of AgNPs on mycorrhizal growth and AM fungal communities, as well as the GRSP contents in maize (Zea mays L.) soils, with a pot experiment. The contributions of GRSP to soil organic C and the correlations of GRSP with soil organic C were also evaluated. The results indicated that AgNPs decreased the mycorrhizal colonization, AM fungal biomass, and diversity indices, and strongly shifted the community composition of AM fungi with a reduction in Acaulosporaceae and an enrichment in Glomeraceae. Additionally, AgNPs also decreased the soil’s easily extractable (EE) GRSP and total (T) GRSP contents, resulting in lower contributions of EE-GRSP-C and T-GRSP-C to the soil organic C. Linkage analyses revealed that AM fungal abundances have positive correlations with EE- and T-GRSP, and EE- and T-GRSP also positively correlated with soil organic C, indicating that the negative effects of AgNPs on AM fungal abundances and communities were extended to AM-fungal-associated C processes. Altogether, our study found that AgNPs decreased the AM fungal abundances shaped AM fungal communities, and reduced the soil GRSP content, which might subsequently be unfavorable for soil C storage.

Bioprospecting for plant resilience to climate change: mycorrhizal symbionts of European and American beachgrass (Ammophila arenaria and Ammophila breviligulata) from maritime sand dunes.

Climate change and global warming have contributed to increase terrestrial drought, causing negative impacts on agricultural production. Drought stress may be addressed using novel agronomic practices and beneficial soil microorganisms, such as arbuscular mycorrhizal fungi (AMF), able to enhance plant use efficiency of soil resources and water and increase plant antioxidant defence systems. Specific traits functional to plant resilience improvement in dry conditions could have developed in AMF growing in association with xerophytic plants in maritime sand dunes, a drought-stressed and low-fertility environment. The most studied of such plants are European beachgrass (Ammophila arenaria Link), native to Europe and the Mediterranean basin, and American beachgrass (Ammophila breviligulata Fern.), found in North America. Given the critical role of AMF for the survival of these beachgrasses, knowledge of the composition of AMF communities colonizing their roots and rhizospheres and their distribution worldwide is fundamental for the location and isolation of native AMF as potential candidates to be tested for promoting crop growth and resilience under climate change. This review provides quantitative and qualitative data on the occurrence of AMF communities of A. arenaria and A. breviligulata growing in European, Mediterranean basin and North American maritime sand dunes, as detected by morphological studies, trap culture isolation and molecular methods, and reports on their symbiotic performance. Moreover, the review indicates the dominant AMF species associated with the two Ammophila species and the common species to be further studied to assess possible specific traits increasing their host plants resilience toward drought stress under climate change.

Plant and soil responses to tillage practices change arbuscular mycorrhizal fungi populations during crop growth.

Tillage practices can substantially affect soil properties depending on crop stage. The interaction between tillage and crop growth on arbuscular mycorrhizal fungi (AMF) communities remains unclear. We investigated the interactions between four tillage treatments (CT: conventional tillage, RT: reduced tillage, NT: no tillage with mulch, and SS: subsoiling with mulch), maintained for 25 years, and two wheat growth stages (elongation stage and grain filling stage) on AMF diversity and community composition. The AMF community composition strongly changed during wheat growth, mainly because of changes in the relative abundance of dominant genera Claroideoglomus, Funneliformi, Rhizophagu, Entrophospora, and Glomus. Co-occurrence network analysis revealed that the grain filling stage had a more complex network than the elongation stage. Redundancy analysis results showed that keystone genera respond mainly to changes in soil organic carbon during elongation stage, whereas the total nitrogen content affected the keystone genera during grain filling. Compared with CT, the treatments with mulch, i.e., NT and SS, significantly changed the AMF community composition. The change of AMF communities under different tillage practices depended on wheat biomass and soil nutrients. NT significantly increased the relative abundances of Glomus and Septoglomus, while RT significantly increased the relative abundance of Claroideoglomus. Our findings indicate that the relative abundance of dominant genera changed during wheat growth stages. Proper tillage practices (e.g., NT and SS) benefit the long-term sustainable development of the Loess Plateau cropping systems.

Distinct response patterns of soil micro-eukaryotic communities to early-season and late-season precipitation in a semiarid grassland

Semiarid ecosystems are susceptible to changes in precipitation regimes. However, how soil micro-eukaryote communities in semi-arid ecosystems respond to variations in the seasonal distribution of precipitation remains elusive. A 5-year field experiment was performed to investigate the effect of changed precipitation distributions throughout the growing season on soil micro-eukaryotic communities in the temperate steppe. Early-season precipitation did not significantly affect the biomass of arbuscular mycorrhizal fungi (AMF) nor the composition and structure of AMF and protist communities. Late-season precipitation significantly increased the biomass of AMF while significantly altering the relative abundance of dominant genera in AMF and protist communities. There was a clear difference in the community structure of AMF and protists between the late-season precipitation and natural precipitation. In addition, late-season precipitation decreased the amount of consumer protists but enhanced the abundance of parasitic protists. These results indicate that the impact of precipitation limitations in the middle growing season can be weakened by increased precipitation in the early growing seasons, while an increase in precipitation later in the growing season does not improve the impact of a decrease in precipitation in the middle growing season. Our findings highlight the potential impact of intra-annual changes in precipitation in soil micro-eukaryotic communities in arid and semiarid regions.

Greater change in arbuscular mycorrhizal fungal richness as a response to short-term rainfall exclusion across the North American monsoon season

Arid ecosystems around the world are projected to experience reduced and more infrequent precipitation events. The effects of reduced rainfall are well understood for plants and aboveground interactions; however, the effect of rainfall on belowground microbial interactions remains understudied. Here, we illustrate the strength and direction of change that short-term manipulative rainfall exclusion treatments have on the composition and relative abundance of Arbuscular Mycorrhizal (AM) fungal communities throughout the monsoon season in the Sonoran Desert. Additionally, we use these rainfall exclusion treatments to further understand the impact of soil moisture on labile forms of nitrogen and phosphorous in a natural environment. Rainfall exclusion treatments were installed to remove 0% (control), 60% (moderate exclusion), and 80% (high exclusion) of rainfall over a single wet season. AM fungal community composition varied among rainfall treatments and across the monsoon season, where change was dependent on initial conditions within treatments. Phosphorous content was also a strong predictor of AM fungal composition and relative abundance. By the end of the season, the difference in AM fungal richness was influenced by rainfall exclusion, with the greatest positive change in richness in the moderate rainfall exclusion treatments. Lastly, AM fungal community turnover was predicted by rainfall exclusion treatments, where rainfall contributed to greater turnover in the control treatment in comparison to other treatments. This study further illustrates the complex association between soil abiotic factors, how they are influenced by environmental stress, and how in turn cause shifts in AM fungal communities.

Arbuscular mycorrhizal fungal community association determines the production of flavonoids and chlorogenic acid in Acer truncatum Bunge

Arbuscular mycorrhizal (AM) fungi can affect plant secondary metabolic pathways, but how the composition and function of AM fungal communities affect the secondary metabolite content of Acer truncatum Bunge remains unknown. Ten typical A. truncatum plantations were used in southern Shaanxi province. The entropy weight method was applied to construct two grades of A. truncatum tree plantations (ordinary and superior). The interaction between AM fungi and trees in the different grades of plantations was compared. The effects of AM fungal community, soil fertility, climatic factors, and plant nutrients on the contents of flavonoids and chlorogenic acid in leaves were studied. There were no differences in the α and β diversity of AM fungal associations among different grades of trees, but the hyphal colonization rate and co-occurrence network characteristics were different. There were no differences in plant height and diameter at breast height (DBH), but higher flavonoid and chlorogenic acid contents were found in the leaves of superior trees compared to ordinary trees, and this difference was attributed to variations in their AM fungal communities. For A. truncatum trees of similar growth (same height and DBH), the abundance of AM fungi was positively correlated with leaf flavonoids and chlorogenic acid contents in superior tree grade stands, but negatively correlated in ordinary tree stands. The positive correlation between leaf flavonoid content and soil fertility in superior tree grade was mediated by the β diversity of AM fungi recruited in this environment. The relative abundance of VTX00069 and VTX00156 was positively correlated with leaf flavonoid and chlorogenic acid contents, which provides direction for the selection of AM fungi that promote flavonoids and chlorogenic acid production in A. truncatum leaves. Overall, the effect of specific AM fungal communities in the rhizosphere soil of A. truncatum on its flavonoids and chlorogenic acid contents is direct and important. This study provides new insights into enhancing the production of secondary metabolites in A. truncatum.

Influence of plant species, mycorrhizal inoculant, and soil phosphorus level on arbuscular mycorrhizal communities in onion and carrot roots.

Arbuscular mycorrhizal fungi (AMF) are ancient and ecologically important symbionts that colonize plant roots. These symbionts assist in the uptake of water and nutrients, particularly phosphorus, from the soil. This important role has led to the development of AMF inoculants for use as biofertilizers in agriculture. Commercial mycorrhizal inoculants are increasingly popular to produce onion and carrot, but their specific effects on native mycorrhizal communities under field conditions are not known. Furthermore, adequate availability of nutrients in soils, specifically phosphorus, can reduce the diversity and abundance of AMF communities in the roots. The type of crop grown can also influence the composition of AMF communities colonizing the plant roots. This study aimed to investigate how AMF inoculants, soil phosphorus levels, and plant species influence the diversity of AMF communities that colonize the roots of onion and carrot plants. Field trials were conducted on high organic matter (muck) soil in the Holland Marsh, Ontario, Canada. The treatments included AMF-coated seeds (three to five propagules of Rhizophagus irregularis per seed) and non-treated onion and carrot seeds grown in soil with low (~46 ppm) and high (~78 ppm) phosphorus levels. The mycorrhizal communities colonizing the onion and carrot roots were identified by Illumina sequencing. Five genera, Diversispora, Claroideoglomus, Funneliformis, Rhizophagus, and Glomus, were identified in roots of both plant species. AMF communities colonizing carrot roots were more diverse and richer than those colonizing onion roots. Diversispora and Funneliformis had a 1.3-fold and 2.9-fold greater abundance, respectively, in onion roots compared to carrots. Claroideoglomus was 1.4-fold more abundant in carrot roots than in onions. Inoculation with R. irregularis increased the abundance and richness of Rhizophagus in AMF communities of onion roots but not in carrot roots. The soil phosphorus level had no effect on the richness and diversity of AMF in the roots of either crop. In summary, AMF inoculant and soil phosphorus levels influenced the composition of AMF communities colonizing the roots of onion and carrot plants, but the effects varied between plant species.

Different Responses of Arbuscular Mycorrhizal Fungal Community Compositions in the Soil and Roots to Nitrogen Deposition in a Subtropical Cunninghamia lanceolata Plantation in China

Elevated nitrogen (N) deposition may stimulate a plant’s dependency on arbuscular mycorrhizal (AM) fungi in phosphorus (P)-deficient subtropical forests. However, the ecological assembly processes and the responses of AM fungal diversity and community structure to N deposition in both the roots and rhizosphere are still unclear. We collected root and soil samples from a Cunninghamia lanceolata plantation forest after four years of N addition and examined the community structure and assembly of AM fungi. Elevated N deposition decreased the AM fungal community diversity in both rhizosphere soil and roots. Glomeraceae was the dominant family of the AM fungal community in both soil and roots across all N addition treatments, followed by Gigasporaceae and Ambisporaceae. However, N addition induced differential variation in the community composition of AM fungi between soil and roots. For soil AM fungi, N addition decreased the Glomeraceae abundance and increased the Gigasporaceae and Ambisporaceae abundance. In contrast, the root AM fungal community was dominated by Glomeraceae under N addition treatments. Furthermore, N addition increased the deterministic community assembly that acted as an environmental filter for soil AM fungi. In contrast, N addition decreased the importance of determinism, implying that the selection of plants on root AM fungi decreased with increasing N addition. Altogether, our findings suggest that the community structure of AM fungi responds differently to N deposition in the soil and roots in subtropical forests and highlight the important role of soil AM fungi in helping host plants respond to N deposition.

Responses of the arbuscular mycorrhizal fungi community to warming coupled with increased drought in an arid desert region

Warming coupled with precipitation changes induced by climate change profoundly affect desert ecosystem functions in global drylands. Arbuscular mycorrhizal fungi (AMF) play a crucial role in such ecosystems by regulating energy and nutrient exchange. However, little is known about how AMF communities respond to warming coupled with reduced precipitation (W + RP). We evaluated the impacts of 0.5 °C and 1.5 °C increase in temperature coupled with 5 % and 8 % reductions in total annual precipitation (0.5 °C W + 5 % RP, 1.5 °C W + 8 % RP) on AMF communities and the main ecological processes structuring AMF community assemblies in the rhizosphere soil of typical winter annual plants in the Tengger Desert, northwest China. The results showed that warming coupled with reduced precipitation could significantly alter the composition, abundance, and diversity of AMF communities. Both AMF biomass and AMF diversity increased in the 0.5 °C W + 5 % RP treatment but decreased in the 1.5 °C W + 8 % RP treatment. The 1.5 °C W + 8 % RP treatment significantly reduced root biomass and the AMF colonization rate but increased the specific root length, indicating a trade-off between fine roots and their symbiotic AMF. The AMF community was phylogenetically random in the 0.5 °C W + 5 % RP treatment but appeared clustered in the 1.5 °C W + 8 % RP treatment, implying that more pronounced warming coupled with reduced precipitation can promote the deterministic assembly of the AMF community. We provide a conceptual framework for comprehending the mechanisms underlying the effects of warming coupled with reduced precipitation on AMF communities, incorporating biological and geochemical processes. Overall, the findings of this study suggest that AMF abundance and diversity and the main ecological processes driving AMF assemblages respond differently to more pronounced compared to less intensive warming coupled with reduced precipitation. Importantly, higher warming coupled with a reduction in precipitation reduced plant dependence on AMF and resulted in stronger environmental filtration by significantly reducing soil water content.

Long-term N addition reduced the diversity of arbuscular mycorrhizal fungi and understory herbs of a Korean pine plantation in northern China

With the development of agriculture and industry, the increase in nitrogen (N) deposition has caused widespread concern among scientists. Although emission reduction policies have slowed N releases in Europe and North America, the threat to biodiversity cannot be ignored. Arbuscular mycorrhizal (AM) fungi play an important role in the establishment and maintenance of plant communities in forest ecosystems, and both their distribution and diversity have vital ecological functions. Therefore, we analyzed the effects of long-term N addition on AM fungi and understory herbaceous plants in a Korean pine plantation in northern China. The soil properties, community structure, and diversity of AM fungi and understory herbaceous plants were detected at different concentrations of NH4NO3 (0, 20, 40, 80 kg N ha−1 year−1) after 7 years. The results showed that long-term N deposition decreased soil pH, increased soil ammonium content, and caused significant fluctuations in P elements. N deposition improved the stability of soil aggregates by increasing the content of glomalin-related soil protein (GRSP) and changed the AM fungal community composition. The Glomus genus was more adaptable to the acidic soil treated with the highest N concentration. The species of AM fungi, understory herbaceous plants, and the biomass of fine roots were decreased under long-term N deposition. The fine root biomass was reduced by 78.6% in the highest N concentration treatment. In summary, we concluded that long-term N deposition could alter soil pH, the distribution of N, P elements, and the soil aggregate fractions, and reduce AM fungal and understory herb diversity. The importance of AM fungi in maintaining forest ecosystem diversity was verified under long-term N deposition.

Impacts of Lithology and Slope Position on Arbuscular Mycorrhizal Fungi Communities in a Karst Forest Soil.

The influence of lithology and slope position on arbuscular mycorrhizal fungi (AMF) communities has been explored in various ecosystems, but there is a limited understanding of these mechanisms in karst regions. This study focused on typical karst hills with contrasting lithologies, specifically dolomite and limestone. Additionally, three slope positions (upper, middle, and lower) were investigated within each hill in karst forest ecosystems. Total phosphorus (TP) content in the soil was higher in dolomite compared to limestone. Conversely, exchangeable calcium (Ca) was lower in dolomite than in limestone. Notably, the lithology, rather than the slope position, exerted a significant impact on AMF diversity and abundance and the presence of specific AMF taxa. Dolomite exhibited greater AMF richness and a higher Shannon index in comparison to limestone when not accounting for slope position. The AMF community composition differed between dolomite and limestone. For instance, without considering slope position, the relative abundance of Acaulospora, Diversispora, and Paraglomus was higher in dolomite than in limestone, while the relative abundance of Claroideoglomus displayed an opposing trend. Furthermore, a more complex interaction among AMF taxa was observed in dolomite as compared to limestone, as evidenced by an increase in the number of nodes and edges in the co-occurrence networks within the dolomite. The genera Glomus, Claroideoglomus, and Diversispora exhibited a higher number of links with each other and with other AMF taxa. The study identified TP and Ca as the primary factors determining variations in AMF diversity between dolomite and limestone. Consequently, it is imperative to consider the underlying lithology and soil conditions when addressing the restoration of degraded karst hilly areas.

Higher colonization but lower diversity of root-associated arbuscular mycorrhizal fungi in the topsoil than in deep soil

Arbuscular mycorrhizal fungi (AMF) colonizing plant roots play a pivotal role in maintaining soil nutrient cycling and ecosystem stability, and this role may vary in different habitat environments. However, the influence of soil depth on root AMF colonization, diversity, and the complex interactions among AMF taxa is still not well understood. In this study, we investigated the frequency, intensity, and abundance of root AMF colonization, as well as root AMF diversity, composition, and co-occurrence patterns across three soil depths: 0–20 cm, 20–40 cm, and the soil-rock mixing layer. Soil nutrients (e.g., organic matter, nitrogen, and phosphorus) and root biomass were higher in the 0–20 cm layer than in the soil-rock mixing layer, while soil pH showed an opposite relationship. The higher root biomass in the upper soil layer may enhance root secretions and exudates, thereby promoting root AMF colonization. In contrast, the lower soil nutrient content and higher soil pH observed in the 20–40 cm and soil-rock mixing layers may contribute to greater AMF diversity in the deeper soil layers compared to the topsoil. Although no significant differences were observed in the composition of the root AMF community, specific amplicon sequence variants affiliated with Glomus, Racocetra, and unclassified taxa were more enriched in the 20–40 cm and soil-rock mixing layers compared to the 0–20 cm layer. Network analysis revealed that deep soil, compared to topsoil, enhances interactions among root AMF by intensifying competitive relationships. This suggests that the complex interactions among root AMF taxa within deep soil contribute to the resilience of root AMF in resource-scarce conditions, particularly in the 20–40 cm layer and the soil-rock mixing layer. At the genus level, Glomus, Racocetra, and unclassified taxa emerged as keystone taxa due to their prominent linkage with other root AMF groups. Collectively, the results suggest that higher soil nutrient levels and root biomass can promote root mycorrhizal colonization but suppress AMF diversity and weaken interactions among root AMF taxa in the upper soil layer compared to deeper soil layers. Furthermore, the distinct functions of AMF colonization and diversity at different soil depths should be considered when evaluating vegetation reconstruction in karst ecosystems with varied soil depth distribution.

Habitat heterogeneity drives arbuscular mycorrhizal fungi and shrub communities in karst ecosystems

Arbuscular mycorrhizal fungi (AMF) constitute one of the factors that regulate the success of vegetation restoration. Karst ecosystems are heterogenous in nutrient content and plant communities because of preferential water fluxes within cracks and gullies in the soil parent material. The effects of habitat on soil nutrients, shrub, and AMF diversity in karst ecosystems are yet to be established. Thus, we investigated the diversity of shrubs and AMF within three habitats: i) rocky soil surface (Rock), ii) soil surface (Soil), and iii) rocky gully (Gully) in a typical karst shrub ecosystem. We observed that AMF diversity was independent of the sampling location, whereas AMF abundance and the shrub Shannon index increased with sampling distance, reaching a plateau in a sampling area of 1000 m2. The AMF community composition was driven by dominating shrubs (Vitex negundo, Tirpitzia ovoidea). Higher shrub diversity and AMF abundance occurred in Rock than in Soil and Gully areas, suggesting higher habitat heterogeneity in Rock areas. Based on co-occurrence network analysis, interactions with a high link number among the AMF taxa were stronger in Rock than in Gully because the network complexity in the Rock areas strongly depended on symbiosis with AMF taxa to cope with high habitat heterogeneity. The Random forest model revealed that AMF abundance was mainly affected by available phosphorous, total potassium, and shrub diversity. Available phosphorous, soil pH, and exchangeable Ca2+, rather than plant diversity, were the main factor controlling AMF community composition. Overall, the results suggest that the increase in shrub diversity raised AMF abundance and richness, and strengthened the interactions among AMF taxa because of nutrient exchange. Thus, increasing habitat heterogeneity with abundant shrub diversity, but soil nutrient limitation, enriches AMF abundance and diversity.

[Effects of Annual Crop Rotation and Fallow on Soil AMF Community and Aggregate Stability].

To investigate the effects of crop rotation and fallow on the community composition of arbuscular mycorrhizal fungi (AMF) and the stability of soil aggregates, AMF community and aggregates were measured using Illumina MiSeq high-throughput sequencing and wet screening methods in red soil of sloping farmland. The AMF community and its relationship with soil factors and aggregate stability were studied under the four treatments of vetch rotation corn (V-C), pea rotation corn (P-C), winter fallow corn (F-C), and annual fallow (F-F). The results showed that the aggregate content of >2 mm, R0.25, and MWD in the F-F, V-C, and P-C treatments were significantly higher than those in F-C (P<0.05), and the aggregate content of <0.25 mm was significantly lower than that of F-C (P<0.05). The ACE, Chao1, and Shannon indexes of the F-F treatment were 29.56%, 35.78%, and 45.55% higher than those of the F-C treatment, respectively. Glomus was the dominant genus of AMF communities under all treatments, whereas Scutellospora showed a significant difference among the treatments (P<0.05). PCoA analysis showed that PC1 and PC2 together explained 29.99% and 22.40% of the difference in the AMF community composition, respectively. The correlation analysis showed that there was a significant negative correlation between Scutellospora and alkaline nitrogen (AN) and organic matter (SOM) (P<0.05), a significant positive correlation between Scutellospora and available potassium (AK) (P<0.05), and a significant positive correlation between Glomus and alkaline nitrogen (P<0.05). RDA analysis showed that AMF diversity (Shannon index) and Scutellospora were significantly and positively correlated with aggregate content >2 mm and 2-1 mm, respectively (P<0.05). Therefore, annual fallow and vetch rotation corn were conducive to improving the stability of soil aggregates and changing the composition of the AMF community. The research results provide a theoretical basis and reference for the annual rotation system to improve soil quality and implement a reasonable crop rotation and fallow pattern in southern China.

Electrical Conductivity and pH Are Two of the Main Factors Influencing the Composition of Arbuscular Mycorrhizal Fungal Communities in the Vegetation Succession Series of Songnen Saline-Alkali Grassland.

Arbuscular mycorrhizal fungi (AMF) are widely distributed microorganisms in the soil, playing an important role in vegetation succession, plant community diversity, and improving soil physicochemical properties. In this study, morphological identification and high-throughput sequencing technology were used to comprehensively analyze the AMF community composition and diversity at different succession stages of Songnen saline-alkali grassland. To determine the root colonization status of plants collected in the field, a colonization system was established using late-succession plants as host plants to verify the existence of mycorrhizal symbiosis and the matching phenomenon of AMF in Songnen saline-alkali grassland. The results indicated that both morphological methods and high-throughput sequencing technology showed that glomus was the dominant genus of AMF in Songnen saline grassland. Redundancy analysis (RDA) and linear regression analysis showed that electrical conductivity (EC) and pH were the main environmental factors affecting AMF species diversity and community structure in the succession sequence of Songnen saline grassland. In addition, the results of root colonization identification and the colonization system test in the field showed that AMF successfully colonized vegetation at different succession stages and had mycorrhizal symbiosis. The results of this study could help to understand the AMF community of Songnen saline-alkali grassland as well as provide a reference and basis for optimizing the AMF community structure of Songnen saline-alkali grassland through human intervention in the future and using mycorrhizal technology to restore and rebuild the degraded ecosystem of Songnen saline-alkali grassland.

Native mycorrhizal communities in maize roots as affected by plant genotype, starter fertilization and a seed-applied biostimulant

Background and aimsOne of the most promising strategies for sustainable intensification of crop production involves the utilization of beneficial root-associated microorganisms, such as plant growth-promoting bacteria and arbuscular mycorrhizal fungi (AMF). The aim of this study was to investigate whether a seed-applied biostimulant, based on the bacterial strain Bacillus amyloliquefaciens IT-45 and a plant polysaccharide extract, and crop enhancement tools, such as hybrids with contrasting early vigor and nitrogen (N) plus phosphorus (P) starter fertilization, and their interactions, shape the communities of native root-colonizing AMF symbionts in maize.MethodsA factorial growth chamber experiment was set up with two maize genotypes in natural soil. Mycorrhizal colonization was evaluated after root staining. The diversity and composition of AMF communities were assessed by PCR-DGGE of the 18S rRNA gene and amplicon sequencing.ResultsN and P fertilization determined a consistent reduction of AMF root colonization and, in combination of biostimulant, a reduction of AMF richness. The biostimulant alone generally did not affect AMF colonization or the community biodiversity. In addition the effect of the two factors were modulated by maize genotype. In all treatments, predominant AMF were represented by Glomus sp. and Funneliformis mosseae, while populations of the genus Rhizoglomus were rarely detected in biostimulant and NP fertilization treatments.ConclusionThe results of this study increase our understanding of how the biostimulant seed treatment may affect native AMF communities, depending on NP fertilization and maize genotype and may improve the implementation of innovative tools in sustainable and resilient agroecosystems.

Plant-symbiotic fungal diversity tracks variation in vegetation and the abiotic environment along an extended elevational gradient in the Himalayas.

Arbuscular mycorrhizal (AM) fungi can benefit plants under environmental stress, and influence plant adaptation to warmer climates. However, very little is known about the ecology of these fungi in alpine environments. We sampled plant roots along a large fraction (1941-6150m asl) of the longest terrestrial elevational gradient on Earth and used DNA metabarcoding to identify AM fungi. We hypothesized that AM fungal alpha and beta diversity decreases with increasing elevation, and that different vegetation types comprise dissimilar communities, with cultured (putatively ruderal) taxa increasingly represented at high elevations. We found that alpha diversity of AM fungal communities declined linearly with elevation, whereas within-site taxon turnover (beta diversity) was unimodally related to elevation. Composition of AM fungal communities differed between vegetation types and was influenced by elevation, mean annual temperature and precipitation. In general, Glomeraceae taxa dominated at all elevations and vegetation types, however, higher elevations were associated with increased presence of Acaulosporaceae, Ambisporaceae and Claroideoglomeraceae. Contrary to our expectation, the proportion of cultured AM fungal taxa in communities decreased with elevation. These results suggest that, in this system, climate-induced shifts in habitat conditions may facilitate more diverse AM fungal communities at higher elevations but could also favour ruderal taxa.

Durum wheat-lentil relay intercropping enhances soil mycorrhizal activity but does not alter structure of arbuscular mycorrhizal fungal community within roots

In intercropping systems, crop species select host-adapted microorganisms and influence the associated plant-microbial interactions like in the case of arbuscular mycorrhizal fungi (AMF). Attempts to assess the impact of intercropping on the activity, diversity, and community composition of AMF remain inconclusive, more so in intercropping systems involving traditional Mediterranean crops such as durum wheat and lentils. We carried out field experiments in Central Italy to assess the impact of relay intercropping durum wheat (Triticum durum Desf. cv. Minosse) and lentil (Lens culinaris Medik. cv. Elsa) on soil mycorrhizal inoculum potential (MIP) (2019 and 2020), AMF root colonization (2019, 2020, and 2021), and root AMF diversity and community composition (2020 and 2021), compared to the respective sole crops. Results showed that relay intercropping enhanced lentil grain yield and durum wheat grain protein concentration but marginally reduced durum wheat grain yield and lentil grain protein concentration. In addition, relay intercropping enhanced soil mycorrhizal activity but differentially influenced mycorrhizal root colonization compared to sole cropping. Sequencing analyses generated a total of 234 amplicon sequence variants belonging to Glomeromycota, which were assigned to 31 virtual taxa using the MaarjAM reference database. Glomeraceae and Claroideoglomeraceae were the most abundant taxa but had contrasting abundances in 2020 and 2021. The overall changes in AMF species diversity and community structure were affected by the interaction between crop species and year, and not by intercropping. Claroideoglomus and Septoglomus showed a strong association with lentil roots while Rhizophagus and Paraglomus were associated with durum wheat roots in 2020, affirming host genotype-AMF preferences. The principal component analysis showed that grain protein concentration was associated with selected mycorrhizal parameters such as community richness and AMF root colonization. Further studies on the functional analysis of the different AMF communities selected by the crop genotype and year may reveal the importance of intercropping in maintaining soil functionality and productivity under low-input systems.

PHOSPHORUS FRACTIONS AND ARBUSCULAR MYCORRHIZAL FUNGI AS INFLUENCED BY FOREST CONVERSION IN CENTRAL HIGHLANDS OF KENYA

&lt;p&gt;&lt;strong&gt;Background:&lt;/strong&gt; Forest conversion to other land use types lead to changes in soil physico-chemical properties and a reduction in soil fertility. Although forest conversion is extensively recognized to alter soil properties, the influence on distribution of soil phosphorus (P) fractions and abundance and diversity of soil biota is not well explored. &lt;strong&gt;Objective:&lt;/strong&gt; To assess the effects of converting undisturbed natural forest to plantation forest (cypress), grazed pastures and potato fields on soil phosphorus (P) fractions and abundance and diversity of arbuscular mycorrhizal fungi (AMF) in Nyandarua County, Kenya. &lt;strong&gt;Methodology:&lt;/strong&gt; Transects laid out in triplicate were established in each land use type. In potato fields and grazed pastures, transects measured 50 m with three sampling points established 15 m apart along each transect, each point measuring 1 m² divided into 25 grids with each grid being 400 cm². Transect length was increased to 150 m in forest sites due to relatively larger size of the area studied and sampling points were placed at 50 m apart, each point measuring 25 m² and divided into 1² m grids. Soil and plant samples were randomly collected from sampling points and were used to determine chemical properties, soil P fractions and AMF spore examination. Data were analyzed by analysis of variance (ANOVA). &lt;strong&gt;Results:&lt;/strong&gt; Soil chemical properties were significantly (&lt;em&gt;p&lt;/em&gt;&amp;lt;0.001) higher in natural forest compared to potato fields, grazed pasture and cypress forest. On the contrary, readily labile and moderately labile P was higher in fields cultivated with potato (125.3 mg and 258.2 mg P kg&lt;sup&gt;-1&lt;/sup&gt;, respectively) than in natural forest (51.1 mg and 95.3 mg P kg&lt;sup&gt;-1&lt;/sup&gt;) and cypress forest (36.4 mg and 82.7 mg P kg&lt;sup&gt;-1&lt;/sup&gt;, respectively). However, non-labile P was higher in natural forest (599.1 mg P kg&lt;sup&gt;-1&lt;/sup&gt;) and lower in cypress forest (251.3 mg kg&lt;sup&gt;-1&lt;/sup&gt;). Of the ten AMF genera identified, only &lt;em&gt;Glomus&lt;/em&gt; and &lt;em&gt;Acaulospora&lt;/em&gt; were significantly (&lt;em&gt;p&lt;/em&gt;&amp;lt;0.01) affected by land use change, where they were more abundant in fields cultivated with potato than the other three land use types. Land use type did not significantly influence diversity and richness in AMF. However, AMF composition varied across the land use types. &lt;strong&gt;Implication:&lt;/strong&gt; Land use change may negatively affect soil chemical properties, enhance redistribution of soil P, and change AMF community composition, and this could have long-term implications on soil fertility. &lt;strong&gt;Conclusion:&lt;/strong&gt; Land use change from natural ecosystems to croplands, grazed pastures and tree plantations alter soil chemical properties, AMF composition and spore abundance, and redistribute soil P fractions by increasing labile P and reducing non-labile P fractions showing that the type of land use chosen significantly influence soil physical and chemical properties and soil biodiversity.&lt;/p&gt;

Biochemical characterization and mycorrhizal fungal community of plant species in the Brazilian seasonal dry forest.

Invasive alien plant species (IAPS) have the ability to change the biochemical properties and the arbuscular mycorrhizal fungal (AMF) community structure in their rhizosphere. Organic acids, microbial activity, and AMF play a key role in the invader's spread and also has interactions with the soil chemical factors. Our aim here was to assess the rhizosphere's biochemical factors, AMF community composition, and soil chemical properties associated with Cryptostegia madagascariensis (IAPS) and Mimosa tenuiflora (endemic plant species) from the Brazilian Seasonal Dry Forest. The highest values of total glomalin (5.87 mg g-1 soil), root colonization (54.5%), oxalic and malic acids (84.21 and 3.01 μmol g-1 , respectively), microbial biomass C (mg kg-1 ), Na+ (0.080 cmolc  kg-1 ), Ca2+ (7.04 cmolc  kg-1 ), and soil organic carbon (4.59 g kg-1 ) were found in the rhizosphere of C. madagascariensis. We found dissimilarities on AMF community structure considering the studied plant species: (i) Racocetra coralloidea, Dentiscutata heterogama, Dentiscutata cerradensis, Gigaspora decipiens, and AMF's richness were highly correlated with the rhizosphere of M. tenuiflora; and (ii). The rhizosphere of C. madagascariensis was highly correlated with the abundance of Claroideoglomus etunicatum, Rhizoglomus aggregatum, Funneliformis mosseae, and Funneliformis geosporum. The results of our study highlight the importance of considering C. madagascariensis as potential hosts for AMF species from Glomerales, and a potential plant species that increase the bioavailability of exchangeable Na and Ca at semi-arid conditions.