Mycorrhizal Response Research Articles

Experimental evidence that poor soil phosphorus (P) solubility typical of drylands due to calcium co-precipitation favors autonomous plant P acquisition over collaboration with mycorrhizal fungi

Calcareous dryland soils are rich in precipitated phosphate and represent >30% of Earth's land, yet the relative importance of phosphorus-acquisition strategies (PAS) among plant species in these systems is not well known. No experiment has investigated potential interactions between varying amounts of added calcium carbonate (CaCO3) and arbuscular mycorrhizal fungi (AMF) on plant performance and PAS which could test for potential mechanisms without the limitations of in-situ comparisons along natural gradients. To fill this knowledge gap, we conducted an experiment with CaCO3 addition, AMF inoculation, and three invasive and five native grassland plants. We expected an increase in soil [CaCO3] of an alkaline subsoil to 1) reduce soil-available phosphorus (P), 2) reduce plant biomass and P uptake, and 3) shift PAS toward increased root mining as Ca-bound P increases. The largest CaCO3 addition reduced available P by as much as 57%. On average, the largest addition of CaCO3 reduced total biomass of plants by 19% and plant uptake of P by 15%. The PAS seemed to have changed, and CaCO3 additions tended to increase an indicator of root exudation (shoot [Mn]) to mobilize Ca-bound P, suggesting plasticity for some inducible root mining, especially Artemisia frigida and Poa secunda. However, CaCO3 and plant species interacted to affect shoot [Mn]. The invasive grass Bromus tectorum was superior at acquiring P (> P uptake, > shoot [Mn]) and thus tolerating low soluble P conditions. Rarely did AMF and CaCO3 interact to affect plant biomass. When they did, mycorrhizal responsiveness did not increase where P was less available, suggesting AMF become less beneficial upon P and Ca coprecipitation. In dryland soils with less soluble P, plants are thus likely to rely more on root mining PAS than mycorrhizal scavenging, except for the invasive forb Euphorbia esula that always benefitted from AMF inoculation.

Microplastic additions modulate intraspecific variability in root traits and mycorrhizal responses across root‐life history strategies

Abstract Microplastics (MP) are recognized as a major pollutant in terrestrial environments, prompting concerns about their effects on plant–soil dynamics. Despite evidence of MP altering soil physicochemical properties, impacts on belowground root traits and arbuscular mycorrhizal (AM) fungi remain poorly explored. Existing research has mainly centred on a few model plant species, emphasizing root biomass, and often employs single polymer types and addition rates that surpass realistic scenarios. To investigate how environmentally relevant mixtures and concentrations of MPs impact plant growth, root trait expression and AM fungal colonization, we conducted a greenhouse experiment using six plant species chosen for their contrasting root life strategies; three species in the Amaryllidaceae family represented resource conservation root traits (Allium fistulosum (onion), Allium tuberosum (chive), Allium porrum (leek)), and three from the Solanaceae family, represented plants with resource acquisitive root traits (Solanum lycopersicum (tomato), Solanum melongena (eggplant), Capsicum annuum (pepper)). MP treatments consisted of control (0% MP), low (0.1% w/w) and high (1% w/w) MP additions, using an environmentally relevant MP mixture of weathered polymer types and shapes. We measured above and belowground biomass, average root trait expression (specific root length (SRL), average root diameter (D) and root tissue density (RTD)), AM fungal colonization, as well as intraspecific variability across MP addition treatments. We found that responses to environmentally relevant additions of MPs were species specific and not determined by root life‐strategy. MPs increased biomass in leek, eggplant and tomato, while decreasing AM fungal colonization in tomato. MP additions had no discernible impact on average root functional trait expression across species. However, the addition of MPs resulted in altered intraspecific variability in root traits and AM fungal colonization, indicating a mechanism for plant tolerance to MPs. To address the impacts of MPs on plant functioning, research needs to focus on environmentally relevant mixtures of MPs, considering various plant species' capacities to tolerate soil contamination and the potential for tipping points under real‐world conditions. Read the free Plain Language Summary for this article on the Journal blog.

Native arbuscular mycorrhizal fungi drive ecophysiology through phenotypic integration and functional plasticity under the Sonoran desert conditions.

Knowledge is scarce to what extent environmental drivers and native symbiotic fungi in soil induce abrupt (short-term), systemic (multiple traits), or specific (a subset of traits) shifts in C3 plants' ecophysiological/mycorrhizal responses. We cultivated an emblematic native C3 species (Capsicum annuum var. glabriusculum, "Chiltepín") to look at how the extreme heat of the Sonoran desert, sunlight regimes (low = 2, intermediate = 15, high = 46 mol m2 d-1) and density of native arbuscular mycorrhizal fungi in soil (low AMF = 1% v/v, high AMF = 100% v/v), drive shifts on mycorrhizal responses through multiple functional traits (106 traits). The warming thresholds were relentlessly harsh even under intensive shade (e.g. superheat maximum thresholds reached ranged between 47-63°C), and several pivotal traits were synergistically driven by AMF (e.g. photosynthetic capacity, biomass gain/allometry, and mycorrhizal colonization traits); whereas concurrently, sunlight regimes promoted most (76%) alterations in functional acclimation traits in the short-term and opposite directions (e.g. survival, phenology, photosynthetic, carbon/nitrogen economy). Multidimensional reduction analysis suggests that the AMF promotes a synergistic impact on plants' phenotypic integration and functional plasticity in response to sunlight regimes; however, complex relationships among traits suggest that phenotypic variation determines the robustness degree of ecophysiological/mycorrhizal phenotypes between/within environments. Photosynthetic canopy surface expansion, Rubisco activity, photosynthetic nitrogen allocation, carbon gain, and differential colonization traits could be central to plants' overall ecophysiological/mycorrhizal fitness strengthening. In conclusion, we found evidence that a strong combined effect among environmental factors in which AMF are key effectors could drive important trade-offs on plants' ecophysiological/mycorrhizal fitness in the short term.

Arbuscular mycorrhizal fungi affect early phenological stages of three secondary vegetation species in a temperate forest

The relationship between arbuscular mycorrhizal fungi (AMF) and secondary vegetation (SV) species at early phenological stages is critical for the successful establishment of these plants on disturbance sites in temperate forests. The main objective of this research is to evaluate the effect of AMF colonization on the early phenological stages (germination and early growth) of three shrub species present in the SV of a temperate forest in central Mexico. We collected soil from different sites in the Abies religiosa forest in central Mexico. We collected seeds of Acaena elongata, Ageratina glabrata, and Solanum pubigerum. We used a controlled experimental design with pasteurized soil (-AMF treatments) and unpasteurized soil (+ AMF treatments). We monitored germination percentage, growth (shoot and root weight and total biomass), AMF root colonization, and the mycorrhizal response index (MRI) for each plant species. All three species tested benefited by AMF, showing higher germination rates. Shoot and root weight and total biomass were significantly higher in the + AMF treatment. Solanum pubigerum showed greater stem length and Ageratina glabrata showed greater root development due to AMF. Ageratina glabrata and Acaena elongata were the most responsive to AMF as indicated by MRI. This research underscores the critical role of AMF in the early phenological stages of SV and highlights the potential ecological benefits of AMF in supporting plant germination and plant growth. These results suggest that AMF enhance germination and early growth of secondary vegetation species, which can be considered in management plans for forest ecosystems.

Measuring leaf and root functional traits uncovers multidimensionality of plant responses to arbuscular mycorrhizal fungi.

While many studies have measured the aboveground responses of plants to mycorrhizal fungi at a single time point, little is known about how plants respond belowground or across time to mycorrhizal symbiosis. By measuring belowground responses and growth over time in many plant species, we create a more complete picture of how mycorrhizal fungi benefit their hosts. We grew 26 prairie plant species with and without mycorrhizal fungi and measured 14 functional traits to assess above- and belowground tissue quality and quantity responses and changes in resource allocation. We used function-valued trait (FVT) modeling to characterize changes in species growth rate when colonized. While aboveground biomass responses were positive, the response of traits belowground were much more variable. Changes in aboveground biomass accounted for 60.8% of the variation in mycorrhizal responses, supporting the use of aboveground biomass response as the primary response trait. Responses belowground were not associated with aboveground responses and accounted for 18.3% of the variation. Growth responses over time were highly variable across species. Interestingly, none of the measured responses were phylogenetically conserved. Mycorrhizal fungi increase plant growth in most scenarios, but the effects of these fungi belowground and across time are more complicated. This study highlights how differences in plant allocation priorities might affect how they utilize the benefits from mycorrhizal fungi. Identifying and characterizing these differences is a key step to understanding the effects of mycorrhizal mutualisms on whole plant physiology.

Mycorrhizal‐herbivore interactions and the competitive release of subdominant tallgrass prairie species

Abstract Plant‐microbial‐herbivore interactions play a crucial role in the structuring and maintenance of plant communities and biodiversity, yet these relationships are complex. In grassland ecosystems, herbivores have the potential to greatly influence the survival, growth and reproduction of plants. However, few studies examine interactions of above‐ and below‐ground grazing and arbuscular mycorrhizal (AM) mycorrhizal symbiosis on plant community structure. We established experimental mesocosms containing an assemblage of eight tallgrass prairie grass and forb species in native prairie soil, maintained under mycorrhizal and nonmycorrhizal conditions, with and without native herbivorous soil nematodes, and with and without grasshopper herbivory. Using factorial analysis of variance and principal component analysis, we examined: (a) the independent and interacting effects of above‐ and below‐ground herbivores on AM symbiosis in tallgrass prairie mesocosms, (b) independent and interacting effects of above‐ and below‐ground herbivores and mycorrhizal fungi on plant community structure and (c) potential influences of mycorrhizal responsiveness of host plants on herbivory tolerance and concomitant shifts in plant community composition. Treatment effects were characterized by interactions between AM fungi and both above‐ground and below‐ground herbivores, while herbivore effects were additive. The dominance of mycorrhizal‐dependent C4 grasses in the presence of AM symbiosis was increased (p < 0.0001) by grasshopper herbivory but reduced (p < 0.0001) by nematode herbivory. Cool‐season C3 grasses exhibited a competitive release in the absence of AM symbiosis but this effect was largely reversed in the presence of grasshopper herbivory. Forbs showed species‐specific responses to both AM fungal inoculation and the addition of herbivores. Biomass of the grazing‐avoidant, facultatively mycotrophic forb Brickellia eupatorioides increased (p < 0.0001) in the absence of AM symbiosis and with grasshopper herbivory, while AM‐related increases in the above‐ground biomass of mycorrhizal‐dependent forbs Rudbeckia hirta and Salvia azurea were eradicated (p < 0.0001) by grasshopper herbivory. In contrast, nematode herbivory enhanced (p = 0.001) the contribution of Salvia azurea to total biomass. Synthesis. Our research indicates that arbuscular mycorrhizal symbiosis is the key driver of dominance of C4 grasses in the tallgrass prairie, with foliar and root herbivory being two mechanisms for maintenance of plant diversity.

Assessing ecological traits of a secondary vegetation species in temperate forests of central Mexico: a case study

Background: Plant species used for reforestation purposes are idoneous if native, the use of species that are present in regeneration sources. High germination percentages under different light conditions and a broad phenological pattern enhance adaptability to environmental heterogeneity. Preference for species responsive to mycorrhizal inoculation is recommended. Questions: Is Solanum pubigerum a widespread species in temperate forests of central Mexico?, under which light conditions germination will be the highest?, how abundant is it in natural regeneration sources?, does inoculation with mycorrhizal fungi benefit its germination and growth? Studied species / data description / Mathematical model: Solanum pubigerum/distribution in central Mexico forests, germination and viability percentages, reproductive phenology, growth dependence on AM fungi/ Kruskal-Wallis test, synchrony, Spearman correlations, ANOVA. Study site and dates: Abies religiosa forest, Mexico City. August 2019 – July 2020. Methods: Seeds of S. pubigerum were exposed to different light qualities, their viability was monitored for two years. Its presence in natural regeneration sources was registered. Reproductive phenology was recorded, and seedlings were inoculated with arbuscular mycorrhizal fungi to assess their growth. Results: Highest seed germination occurred under white light conditions, with sustained viability after two years. The species was found in the seed bank across seasons, less abundantly in seed rain during the dry season. It exhibited extensive flowering and fruiting patterns. Mycorrhiza inoculation significantly boosted seed germination and growth. Conclusions: Solanum pubigerum is suitable for reforestation in central Mexico forests due to its high germination percentages and mycorrhizal responsiveness.

Plant genotype and inoculation with indigenous arbuscular mycorrhizal (AM) fungi modulate wheat productivity and quality of processed products through changes in the frequency of root AM fungal taxa

ContextArbuscular mycorrhizal fungi (AMF) have been extensively applied as biofertilizers in wheat to promote crop productivity. However, variability in AM root colonization, grain yield, and nutrients was observed among wheat genotypes and according to AM genotype and environment. ObjectivesWe hypothesized that wheat response to AM inoculation is more affected by genotype than environment; the response is driven by increases in AM abundance and community structure changes, and not by modification of composition. MethodsWe inoculated an indigenous AM consortium on four old genotypes (Bianco Nostrale, Andriolo, Abbondanza, Sieve) and one modern variety (Bologna) of bread wheat for two years. The effect was evaluated by assessing grain yield, nutrients, and quality of processed products (flour and breadsticks), while the AM abundance and the community composition and structure in roots were characterized, at two plant growth stages, using morphological and molecular tools. ResultsThe functional traits of AMF and plant were better explained by inoculation than by genotype or environment (33 %, 17 %, 4 % of total explained variance), although significant interactions environment x genotype and genotype x inoculation were highlighted. Consistent increases in AM abundance in Sieve and Bologna were associated with positive changes in grain yield and nutrients, supporting the good responsiveness of these genotypes with inoculated AMF, while the plant response of other genotypes was shaped by air temperature and rainfall. However, we did not find significant correlations between changes in AM colonization and mycorrhizal response ratio, with the exception of P and K. After inoculation, AM community composition was similar in all wheat genotypes, but the structure greatly differed among genotypes in interaction with inoculation and plant growth stage. These changes were significantly related to wheat productivity. A Septoglomus taxon, present in the inoculum, was the best predictor of wheat performance. The characterization of the community structure at early crop development and maturity allowed the identification of fast and latest active AM colonizers. Our results showed for the first time that AM inoculation affect the rheological parameters and nutraceuticals of processed products, although the response was modulated by genotype. ConclusionsThe selection of responsive wheat genotypes is fundamental for the positive outcome of inoculation. The positive effects on wheat productivity and field persistence of the inoculated AMF support the use of indigenous consortia that have low impacts on resident AMF. SignificanceOur findings advance the understanding of the facilitative mechanisms that underlie compatibility between AMF and wheat genotypes.

Analysis of cultivar variability in arbuscular mycorrhizal responsiveness in soybean varieties

ABSTRACT In modern agricultural systems, high crop yields depend on the high input of orthophosphate-based fertilizers. Owing to the looming scarcity of rock phosphate in the near future, utilization of arbuscular mycorrhizal (AM) symbiosis for the efficient uptake of phosphorus is a necessary approach to maintain crop yield. Plant responsiveness to AM fungi is assessed based on the difference in biomass between plants with and without AM fungal inoculation. Soybean is a plant which establishes both mycorrhizal and rhizobial symbiosis. Therefore, it is difficult to eliminate the symbiotic effects of rhizobial nitrogen fixation during long-term cultivation until soybean harvest. In this study, Bradyrhizobium diazoefficiens USDA110 was inoculated at the same time as soybean seeds were sown, and soybean was grown under Rhizophagus irregularis inoculated and non-inoculated conditions to verify whether the mycorrhizal inoculation effect was observed at the yield level. In 2013, two soybean cultivars Tachinagaha and Williams 82, were grown at five levels of phosphate availability (0, 5, 10, 20, and 40 kg P 10a−1) in an open greenhouse in Tsukuba, Japan. Among the several growth indices analyzed, seed weight per plant was selected as a reliable indicator of plant response. Mycorrhizal inoculation showed a positive effect on soybean under 20 kg P 10a−1 phosphorus fertilization for Williams 82, while Tachinagaha showed almost no effect. This trend was replicated in 2014 and 2016, indicating that Tachinagaha has a lower AM responsiveness than Williams 82.

Shifts of arbuscular mycorrhizal fungal functioning along a simulated nitrogen deposition gradient

AbstractThe deposition of atmospheric nitrogen can significantly boost the amount of nitrogen available in various ecosystems, potentially altering the mutualistic association between arbuscular mycorrhizal fungi (AMF) and their host plants. Nevertheless, the precise mechanisms and the degree to which externally induced nitrogen‐related changes in AMF functionality might impact Sorghum bicolor (L.) Moench, a plant known for its high mycorrhizal colonization, remains unclear. In this study, the mycorrhizal response affected by environmental N enrichment was addressed by conducting a glasshouse experiment, and four fertilization treatments (N1, N2, N3, and N4, 0, 15, 30, and 60 kg N hm−1 a−1, respectively) were used to simulate N deposition differences over the mycorrhizal response. The changes in mycorrhizal colonization and plant variables during different AMF and N fertilizer applications were investigated. When the gradient's nitrogen levels increased, the mycorrhizal growth response and mycorrhizal nitrogen response showed a pattern of first dropping and then increasing. N‐induced changes in the mycorrhizal response were associated with vesicular colonization, arbuscular colonization, and root‐length colonization. The variation in the mycorrhizal response over the N concentration gradient highlights the critical role of AMF in agroecosystems.

Straw return influences the structure and functioning of arbuscular mycorrhizal fungal community in a rice-wheat rotation system

Straw incorporation is a sustainable soil fertility-building practice, which can affect soil microbial communities. However, how straw incorporation affects arbuscular mycorrhizal fungi (AMF) is not well explored. Here, we studied the impacts of different straw management practices over eight years on the structure and function of AMF communities in a rice-wheat rotation system. The straw managements included no tillage with no straw (NTNS), rotary tillage straw return (RTSR) and ditch-buried straw return (DBSR). The community structure of AMF was characterized using high-throughput sequencing and the mycorrhizal functioning was quantified using an in situ mycorrhizal-suppression treatment. Different straw management practices formed unique AMF community structure, which was closely related to changes in soil total organic carbon, available phosphorus, total nitrogen, ammonium and nitrate. RTSR significantly increased Shannon diversity in 0-10 cm soils while DBSR increased it in 10–20 cm soils when compared with NTNS. DBSR significantly increased hyphal length density in the whole (0–20 cm) ploughing layer, but RTSR only increased it in the subsoil layer (10–20 cm). The mycorrhizal responses of shoot biomass and nutrient (N and P) uptake were positive under both straw incorporation treatments (RTSR and DBSR), but negative under NTNS. AMF community composition was significantly correlated to hyphal length density, and the latter was further a positive predictor for the mycorrhizal responses of plant growth and nutrient uptake. These findings suggest that straw return can affect AMF community structure and functioning, and farmers should manage mycorrhizas to strengthen their beneficial effects on crop production.

Response Of Growth And Production Of Shallot To The Genus Of Mycorrhiza And Npk Fertilizer

Mycorrhizal biofertilizer is a biotechnology agent and bio protector that is environmentally friendly and supports the concept of sustainable agriculture. The purpose of this study was to determine the effect of growth and production of shallots on the application of the genus Mycorrhizae and N,P,K fertilizers. This study used a completely randomized design method with two factors: The first factor was the application of the mycorrhizal genera Glomus (M1), Gigaspora (M2), Acaulospora (M3), and the Mycorrhizal Consortium (M4); and the second factor is 0-gram NPK fertilizer (NPK0), 25-gram NPK fertilizer (NPK25), 50-gram NPK fertilizer (NPK50), 75-gram NPK fertilizer (NPK75). The results of the identification of Glomus spore form is obovoid, the spore wall is more than one layer, yellow in color. Gigaspora spore form is globose, spore walls do not have an inner wall, and the spore is yellowish cream in color. Acaulospora spore is elliptic, has 2 spore walls, spores are yellow. The results of mycorrhizal responses and doses of NPK fertilizer on the growth and production of shallots were not significantly different according to the analysis of variance in all observation parameters, but some treatments consistently produced the highest results among other treatments. The highest treatment was M1.NPK50 produced an average number of shallots of 50 pieces, the number of shallot bulbs averaged 13.4 and the diameter of shallot bulbs averaged 4.9.

Maize, wheat, and soybean root traits depend upon soil phosphorus fertility and mycorrhizal status.

Strong effects of plant identity, soil nutrient availability or mycorrhizal fungi on root traits have been well documented, but their interactive influences on root traits are still poorly understood. Here, three crop species (maize, wheat and soybean) were grown under four phosphorus (P) addition levels (0, 20, 40 and 60mg P kg-1 dry soil), and plants were inoculated with or without five combined arbuscular mycorrhizal fungal (AMF) species. Plant biomass, nutrient contents, root traits (including total root length, average root diameter, specific root length and root tissue density) and plants' mycorrhizal responses were measured. Crop species, P level, AMF, and their interactions strongly affected plant biomass and root traits. P fertilization promoted plant growth but reduced mycorrhizal benefits on plant biomass and nutrient uptake. Root traits of maize were sensitive to P addition only under the non-mycorrhizal condition, whilst most root traits of soybean and wheat plants were responsive to mycorrhizal inoculation but not P addition. Mycorrhizal colonization reduced the root plasticity in response to P fertility for maize but not for wheat or soybean. This study highlights the importance of soil nutrient fertility and mycorrhizal symbiosis in influencing root traits.

Effect of arbuscular mycorrhizal fungi on early growth, root colonization, and chlorophyll content of North Maluku nutmeg cultivars

Abstract This study aimed to investigate the agronomic traits of nutmeg transplanting by arbuscular mycorrhizal fungi (AMF) inoculation. The low-fertility soil of Sofifi North Maluku was subjected to a slow early growth stage of nutmeg cultivars. A completely randomized design was used in the experiment. The first factor was three different AMF doses: 0, 4, and 8 g seedlings−1. The second factor consisted of three cultivars: “Ternate 1,” “Tobelo 1,” and “Makian.” Root colonization and agronomic traits were measured 28 weeks after inoculation and transplantation. Results showed that AMF inoculation increased the AM colonization by 2.5–39.0%, significantly increased the leaf area (LA) (p < 0.01) in all cultivars, and interacted with cultivars to increase chlorophyll a (Chl a) (p < 0.05), chlorophyll b (Chl b) (p < 0.01), and total Chl (p < 0.01). Cultivars “Makian” showed the highest Chl (188.4%) at 8 g seedling−1 doses of AMF that were significantly (p < 0.01) different from the cultivar “Tobelo 1” at the same dose. The largest mycorrhizal response was found in the cultivar “Ternate 1” (biomass increase of 30–37.0%). The cultivar “Ternate 1” produced the largest LA (36.7–106.9%) and shoot dry weight (27.8–45.8%) that were significantly (p < 0.01) different from the other cultivars. The percentage of AM colonization was strongly determined (R 2 = 0.88) by Chl a, Chl b, and K content in leaves. This technology is a breakthrough to increase LA and plant biomass in the early growth stage of nutmeg cultivation.

Mycorrhizal response of Solanum tuberosum to homokaryotic versus dikaryotic arbuscular mycorrhizal fungi.

Arbuscular mycorrhizal fungi (AMF) are obligate plant symbionts of most land plants. In these organisms, thousands of nuclei that are either genetically similar (homokaryotic) or derived from two distinct parents (dikaryotic) co-exist in a large syncytium. Here, we investigated the impact of these two nuclear organizations on the mycorrhizal response of potatoes (Solanum tuberosum) by inoculating four potato cultivars with eight Rhizophagus irregularis strains individually (four homokaryotic and four dikaryotic). By evaluating plant and fungal fitness-related traits four months post inoculation, we found that AMF genetic organization significantly affects the mycorrhizal response of host plants. Specifically, homokaryotic strains lead to higher total, shoot, and tuber biomass and a higher number of tubers, compared to dikaryotic strains. However, fungal fitness-related traits showed no clear differences between homokaryotic and dikaryotic strains. Nucleotype content analysis of single spores confirmed that the nucleotype ratio of AMF heterokaryon spores can shift depending on host identity. Together, these findings continue to highlight significant ecological differences derived from the two distinct genetic organizations in AMF.

Combined Phosphorus and Water stress Conditions Induce Negative Mycorrhizal Response in Maize (Zea mays L.)

Arbuscular mycorrhizal fungi (AMF) confer both positive and negative effects on the plant symbionts, depending on the prevailing growth condition. We investigated the effect of concurrent variations in phosphorus and soil moisture on percentage root colonization (%RC), mycorrhizal growth response (MGR) and drought response index (DRI) of SAMMAZ-16 maize variety in timescale. The experimental factors were AMF inoculation (addition or no addition), P2O5 applications (30, 60 or 90 kg ha-1) and water regimes (100% and 50% of the soil’s field capacity introduced after 4WAS). The result shows that the overall %RC was 62.22% at 8 weeks after sowing (WAS) and 71.33% at 12 WAS. With 30 and 60 kg P2O5 ha-1 application a rate, %RC was significantly higher at 12 WAS than that of similar application rates at 8 WAS. However, %RC was not different between 8 WAS and 12 WAS in 90 kg P2O5 ha-1 application. AMF inoculation tended to equilibrate the shoot growth of the inoculated plants to that of non- inoculated plants that received 50% higher doses of P2O5 under amply watered conditions. Increasing phosphorus application progressively alleviated the negative mycorrhizal response of the plants at the early stage of growth (week 4) and in 50% FC category at the other sampling times. Higher doses of P2O5 application improved the DRI of the maize in both samplings but the trend was more consistent in AMF-inoculated plants. We conclude that AMF inoculation would be detrimental to the growth of SAMMAZ-16 when there is combined phosphorus and water stress factors

Drought Eliminates the Difference in Root Trait Plasticity and Mycorrhizal Responsiveness of Two Semiarid Grassland Species with Contrasting Root System.

Root traits and arbuscular mycorrhizal (AM) fungi are important in determining the access of plants to soil resources. However, whether plants with different root systems (i.e., taproot vs. fibrous-root) exhibit different root trait plasticity and mycorrhizal responsiveness under drought remains largely unexplored. Tap-rooted Lespedeza davurica and fibrous-rooted Stipa bungeana were grown in monocultures in sterilized and live soils, followed by a drought treatment. Biomass, root traits, root colonization by AM fungi, and nutrient availability were evaluated. Drought decreased biomass and root diameter but increased the root:shoot ratio (RSR), specific root length (SRL), soil NO3--N, and available P for the two species. Under control and drought conditions, soil sterilization significantly increased the RSR, SRL, and soil NO3--N for L. davurica, but this only occurs under drought condition for S. bungeana. Soil sterilization significantly reduced AM fungal root colonization of both species, but drought significantly increased it in live soil. In water-abundant conditions, tap-rooted L. davurica may depend more on AM fungi than fibrous-rooted S. bungeana; however, under drought conditions, AM fungi are of equal importance in favoring both plant species to forage soil resources. These findings provide new insights for understanding the resource utilization strategies under climate change.

Nutrient conditions mediate mycorrhizal effects on biomass production and cell wall chemistry in poplar.

Large scale biofuel production from lignocellulosic feedstock is limited by the financial and environmental costs associated with growing and processing lignocellulosic material and the resilience of these plants to environmental stress. Symbiotic associations with arbuscular (AM) and ectomycorrhizal (EM) fungi represent a potential strategy for expanding feedstock production while reducing nutrient inputs. Comparing AM and EM effects on wood production and chemical composition is a necessary step in developing biofuel feedstocks. Here, we assessed the productivity, biomass allocation, and secondary cell wall composition of greenhouse grown Populus tremuloides inoculated with either AM or EM fungi. Given the long-term goal of reducing nutrient inputs for biofuel production, we further tested the effects of nutrient availability and nitrogen:phosphorus stoichiometry on mycorrhizal responses. Associations with both AM and EM fungi increased plant biomass by 14% to 74% depending on the nutrient conditions but had minimal effects on secondary cell wall composition. Mycorrhizal plants, especially those inoculated with EM fungi, also allocated a greater portion of their biomass to roots, which could be beneficial in the field where plants are likely to experience both water and nutrient stress. Leaf nutrient content was weakly, but positively correlated with wood production in mycorrhizal plants. Surprisingly, phosphorus played a larger role in EM plants compared to AM plants. Relative nitrogen and phosphorus availability was correlated with shifts in secondary cell wall composition. For AM associations the benefit of increased wood biomass may be partially offset by increased lignin content, a trait that affects downstream processing of lignocellulosic tissue for biofuels. By comparing AM and EM effects on the productivity and chemical composition of lignocellulosic tissue, this work links broad functional diversity in mycorrhizal associations to key biofuels traits and highlights the importance of considering both biotic and abiotic factors when developing strategies for sustainable biofuel production.

Arbuscular mycorrhizal fungi reduce ammonia emissions under different land-use types in agro-pastoral areas

Ammonia (NH3) emissions, the most important nitrogen (N) loss, always induce a series of environmental problems such as increased the frequency of regional haze pollution, accelerated N deposition, and N eutrophication. Arbuscular mycorrhizal (AM) fungi play key roles in N cycling. However, whether AM fungi can alleviate N losses by reducing NH3 emissions is still unclear. The potential and mechanism by which AM fungi reduce NH3 emissions in five land-use types (grazed grassland, mowed grassland, fenced grassland, artificial alfalfa grassland, and cropland) were explored in this study. The results showed that AM fungal inoculation significantly reduced NH3 emissions and the mycorrhizal responses of NH3 emissions were determined by land-use type. Structural equation modeling (SEM) showed that AM fungi and land-use type directly affected NH3 emissions. In addition, the reduction in NH3 emissions was largely driven by the decline in soil NH4+-N and pH and the increase the abundances of ammonia-oxidizing archaea (AOA) and bacteria (AOB), urease activity and plant N content induced by AM fungal inoculation and land-use type. The present results highlight that reducing the negative influence of agricultural intensification caused by land-use type changes on AM fungi should be considered to reduce N losses in agriculture and grassland ecosystems.

Diverse mycorrhizal maize inbred lines differentially modulate mycelial traits and the expression of plant and fungal phosphate transporters.

Food production is heavily dependent on soil phosphorus (P), a non-renewable mineral resource essential for plant growth and development. Alas, about 80% is unavailable for plant uptake. Arbuscular mycorrhizal fungi may promote soil P efficient use, although the mechanistic aspects are yet to be completely understood. In this study, plant and fungal variables involved in P acquisition were investigated in maize inbred lines, differing for mycorrhizal responsiveness and low-P tolerance, when inoculated with the symbiont Rhizoglomus irregulare (synonym Rhizophagus irregularis). The expression patterns of phosphate transporter (PT) genes in extraradical and intraradical mycelium (ERM/IRM) and in mycorrhizal and control maize roots were assessed, together with plant growth responses and ERM extent and structure. The diverse maize lines differed in plant and fungal accumulation patterns of PT transcripts, ERM phenotypic traits and plant performance. Mycorrhizal plants of the low-P tolerant maize line Mo17 displayed increased expression of roots and ERM PT genes, compared with the low-P susceptible line B73, which revealed larger ERM hyphal densities and interconnectedness. ERM structural traits showed significant correlations with plant/fungal expression levels of PT genes and mycorrhizal host benefit, suggesting that both structural and functional traits are differentially involved in the regulation of P foraging capacity in mycorrhizal networks.