Arbuscular mycorrhizal fungi (AMF) have been shown to effectively mitigate the detrimental effects of heavy metal stress on their plant hosts. Nevertheless, the biological activities of AMF were concurrently compromised. Biochar (BC), as an abiotic factor, had the potential compensate for this limitation. To elucidate the synergistic effects of biotic and abiotic factors, a pot experiment was conducted to assess the impact of biochar and AMF on the growth, physiological traits, and genetic expression in rice plants subjected to Cd stress. The results demonstrated that biochar significantly increased the mycorrhizal colonization rate by 22.19 %, while the combined application of biochar and AMF led to a remarkable enhancement of rice root biomass by 42.2 %. This resulted in a shift in spatial growth patterns that preferentially promoted enhanced underground development. Biochar effectively mitigated the stomatal limitations imposed by Cd on photosynthetic processes. The decrease in IBRv2 (Integrated Biomarker Response version 2) values suggested that the antioxidant system was experiencing a state of remission. An increase of Cd content within the rice root systems was observed, ranging from 33.71 % to 48.71 %, accompanied by a reduction in Cd bioavailability and mobility curtailed its translocation to the aboveground tissues. Under conditions of low soil Cd concentration (Cd ≤ 1 mg·kg-1), the Cd content in rice seeds from the group subjected to the combined treatment remained below the national standard (Cd ≤ 0.2 mg·kg-1). Furthermore, the combined treatment modulated the uptake of Fe and Zn by rice, while simultaneously suppressing the expression of genes associated with Cd transport. Collectively, the integration of biological and abiotic factors provided a novel perspective and methodological framework for safe in-situ utilization of soils with low Cd contamination.

OBJECTIVE: Arbuscular mycorrhizal fungi (AMF) can perform significant functions within sustainable agricultural ecosystems, including vineyards. Increased AMF diversity can be beneficial in promoting plant growth and increasing resilience to environmental changes. To effectively utilise AMF communities and their benefits in vineyard ecosystems, a better understanding of how management systems influence AMF community composition is needed. Moreover, it is unknown whether AMF communities in organically managed vineyards are distinct from those in conventionally managed vineyards.
RESULTS: In this study, vineyards were surveyed across the Marlborough region, New Zealand to identify the AMF communities colonizing the roots of different rootstocks grafted with Sauvignon Blanc and Pinot Noir in both conventional and organic systems. The AMF communities were identified based on spores isolated from trap cultures established with the collected grapevine roots, and by next-generation sequencing technologies (Illumina Miseq). The identified AMF species/genera belonged to Glomeraceae, Entrophosporaceae and Diversisporaceae. The results revealed a significant difference in AMF community composition between rootstocks and in their interaction with management systems.
CONCLUSIONS: These outcomes indicated that vineyard management systems influence AMF recruitment by rootstocks and some rootstocks may therefore be more suited to organic systems due to the AMF communities they support. This could provide an increased benefit to organic systems by supporting higher biodiversity.

Nuclear Ca²⁺ signaling is crucial for symbiotic interactions between legumes and beneficial microbes, such as rhizobia and arbuscular mycorrhizal fungi. Key to generating repetitive nuclear Ca²⁺ oscillations are the ion channels DMI1 and CNGC15. Despite over 20 years of research on symbiotic nuclear Ca²⁺ spiking, important questions remain, including the exact function of the DMI1 channel. This review highlights recent developments that have filled knowledge gaps regarding the regulation of CNGC15 and its interplay with DMI1. We also explore new insights into the evolutionary conservation of DMI1-induced symbiotic nuclear Ca²⁺ oscillations and the roles of CNGC15 and DMI1 beyond symbiosis, such as in nitrate signaling, and discuss new questions this raises. As we delve deeper into the regulatory mechanisms and evolutionary history of these ion channels, we move closer to fully understanding the roles of nuclear Ca²⁺ signaling in plant life.

Arbuscular mycorrhizal fungi (AMF) are obligate symbionts that engage in crucial interactions with plants, playing a vital role in grassland ecology. Our study focuses on the pioneer plant Agropyron cristatum, and we collected soil samples from four degraded grasslands in Yudaokou to investigate the response of community composition to the succession of degraded grasslands. We measured the vegetation status, soil physical and chemical properties, AMF colonization, and spore density in different degraded grasslands. High-throughput sequencing was employed to analyze AMF in soil samples. Correlations among community composition, soil characteristics, and plant factors were studied using principal component and regression analyses. The distribution of AMF in grasslands exhibited variation with different degrees of degradation, with Glomus, Scutellospora, and Diversispora being the dominant genera. The abundance of dominant genera in AMF also varied, showing a gradual increase in the relative abundance of the genus Diversispora with higher degradation levels. AMF diversity decreased from 27.7% to 12.4% throughout the degradation process. Among 180 samples of Agropyron cristatum plants, AMF hyphae and vesicles displayed the highest infection status in non-degraded grasslands and the lowest in severely degraded ones. Peak AMF spore production occurred in August, with maximum values in the 0-10-cm soil layer, and the highest spore densities were found in lightly degraded grasslands. Apart from pH, soil factors exhibited a positive correlation with AMF infection during grassland degradation. Furthermore, changes in AMF community composition were jointly driven by vegetation and soil characteristics, with vegetation coverage and soil organic carbon significantly impacting AMF distribution. Significant differences in AMF variables (spore number and diversity index) were also observed at different soil depths. Grassland successional degradation significantly influences AMF community structure and composition. Our future focus will be on understanding response mechanisms and implementing improvement methods for AMF during grassland degradation and subsequent restoration efforts.

Arbuscular mycorrhizal (AM) fungi are well known for enhancing phosphorus uptake in plants; however, their regulating roles in cation transporting gene family, such as natural resistance-associated macrophage protein (NRAMP), are still limited. Here, we performed bioinformatics analysis and quantitative expression assays of tomato SlNRAMP 1 to 5 genes under nutrient deficiency and cadmium (Cd) stress in response to AM symbiosis. These five SlNRAMP members are mainly located in the plasma or vacuolar membrane and can be divided into two subfamilies. Cis-element analysis revealed several motifs involved in phytohormonal and abiotic regulation in their promoters. SlNRAMP2 was downregulated by iron deficiency, while SlNRAMP1, SlNRAMP3, SlNRAMP4, and SlNRAMP5 responded positively to copper-, zinc-, and manganese-deficient conditions. AM colonization reduced Cd accumulation and expression of SlNRAMP3 but enhanced SlNRAMP1, SlNRAMP2, and SlNRMAP4 in plants under Cd stress. These findings provide valuable genetic information for improving tomato resilience to nutrient deficiency and heavy metal stress by developing AM symbiosis.

This study aimed to investigate the effects of applying arbuscular mycorrhizal fungi (AMF) on maize root growth and yield formation under different soil conditions. This study was conducted under sandy soil (S) and saline-alkali soil (Y), with treatments of AMF application (AM) and no AMF application (CK). The root characteristics, yield, and quality of maize were measured. High-throughput sequencing technology was employed to assess the impact of AMF on the soil microbial community structure, and the correlation between soil microbes and soil physicochemical properties was elucidated. The results show that under both sandy and saline-alkali soil conditions, AMF application significantly enhanced maize root growth, yield, grain quality, and soil available nitrogen (AN), available phosphorus (AP), and available potassium (AK) contents compared to the CK treatment. Soil microbial Alpha diversity analysis indicated that AMF application effectively increased soil microbial diversity and richness. Principal coordinate analysis (PCoA) and microbial community structure analysis revealed significant differences in bacterial communities between AM treatment in sandy soil (SAM) and CK in sandy soil (SCK), and significant differences in both bacterial and fungal communities between AM treatment in saline-alkali soil (YAM) and CK in saline-alkali soil (YCK). Furthermore, significant correlations between microbial communities and soil physicochemical properties were found, such as AN, AP, AK, soil salinity (SS), and organic matter (OM) content. AMF application had a greater impact on bacterial communities than on fungal communities. This study demonstrated that the use of AMF as a bio-fungal fertilizer was effective in improving spring maize yields, especially in terms of yield increase and quality stability in sandy and saline soils, thereby contributing to safe and sustainable cropping practices.

Phosphorus (P), an essential macronutrient for various plant processes, is generally a limiting soil component for crop growth and yields. Organic and inorganic types of P are copious in soils, but their phyto-availability is limited as it is present largely in insoluble forms. Although phosphate fertilizers are applied in P-deficit soils, their undue use negatively impacts soil quality and the environment. Moreover, many P fertilizers are lost because of adsorption and fixation mechanisms, further reducing fertilizer efficiencies. The application of phosphate-solubilizing microorganisms (PSMs) is an environmentally friendly, low-budget, and biologically efficient method for sustainable agriculture without causing environmental hazards. These beneficial microorganisms are widely distributed in the rhizosphere and can hydrolyze inorganic and organic insoluble P substances to soluble P forms which are directly assimilated by plants. The present review summarizes and discusses our existing understanding related to various forms and sources of P in soils, the importance and P utilization by plants and microbes,, the diversification of PSMs along with mixed consortia of diverse PSMs including endophytic PSMs, the mechanism of P solubilization, and lastly constraints being faced in terms of production and adoption of PSMs on large scale have also been discussed.

Arbuscular mycorrhizal fungi (AMF) colonization has been used in constructed wetlands (CWs) to enhance treatment performance. However, its role in azole (fungicide) degradation and microbial community changes is not well understood. This study aims to explore the impact of AMF on the degradation of tebuconazole and its metabolites in CWs. Total organic carbon levels were consistently higher with the colonization of AMF (AMF+; 9.63- 16.37 mg/L) compared to without the colonization of AMF (AMF-; 8.79-14.48 mg/L) in CWs. Notably, tebuconazole removal was swift, occurring within one day in both treatments (p = 0.885), with removal efficiencies ranging from 94.10 % to 97.83 %. That\'s primarily due to rapid substrate absorption at the beginning, while degradation follows with a longer time. Four metabolites were reported in CWs first time: tebuconazole hydroxy, tebuconazole lactone, tebuconazole carboxy acid, and tebuconazole dechloro. AMF decreased the abundance of tebuconazole dechloro in the liquid phase, suggesting an inhibitory effect of AMF on dechlorination processes. Furthermore, tebuconazole carboxy acid and hydroxy were predominantly found in plant roots, with a higher abundance observed in AMF+ treatments. Metagenomic analysis highlighted an increasing abundance in bacterial community structure in favor of beneficial microorganisms (xanthomonadales, xanthomonadaceae, and lysobacter), along with a notable presence of functional genes like codA, NAD, and deaD in AMF+ treatments. These findings highlight the positive influence of AMF on tebuconazole stress resilience, microbial community modification, and the enhancement of bioremediation capabilities in CWs.

Graziella Berta, a well-known mycorrhiza researcher, passed away in her home in Torino (Italy) on March 2nd, 2024, at the age of 75. We were both fortunate to know Graziella personally and to greatly appreciate her professionally, by working closely with her in the same research group in Alessandria (GL) or through many collaborative projects over the years (VGP). Here, we recall some of the milestones in her research and particularly the important contribution she has made to knowledge about plant interactions with mycorrhizal fungi and beneficial rhizosphere bacteria.

CONCLUSIONS: Ants, but not mycorrhizae, significantly affected insect leaf-chewing herbivory on potato plants. However, there was no evidence of mutualistic interactive effects on herbivory. Plants associate with both aboveground and belowground mutualists, two prominent examples being ants and arbuscular mycorrhizal fungi (AMF), respectively. While both of these mutualisms have been extensively studied, joint manipulations testing their independent and interactive (non-additive) effects on plants are rare. To address this gap, we conducted a joint test of ant and AMF effects on herbivory by leaf-chewing insects attacking potato (Solanum tuberosum) plants, and further measured plant traits likely mediating mutualist effects on herbivory. In a field experiment, we factorially manipulated the presence of AMF (two levels: control and mycorrhization) and ants (two levels: exclusion and presence) and quantified the concentration of leaf phenolic compounds acting as direct defenses, as well as plant volatile organic compound (VOC) emissions potentially mediating direct (e.g., herbivore repellents) or indirect (e.g., ant attractants) defense. Moreover, we measured ant abundance and performed a dual-choice greenhouse experiment testing for effects of VOC blends (mimicking those emitted by control vs. AMF-inoculated plants) on ant attraction as a mechanism for indirect defense. Ant presence significantly reduced herbivory whereas mycorrhization had no detectable influence on herbivory and mutualist effects operated independently. Plant trait measurements indicated that mycorrhization had no effect on leaf phenolics but significantly increased VOC emissions. However, mycorrhization did not affect ant abundance and there was no evidence of AMF effects on herbivory operating via ant-mediated defense. Consistently, the dual-choice assay showed no effect of AMF-induced volatile blends on ant attraction. Together, these results suggest that herbivory on potato plants responds mainly to top-down (ant-mediated) rather than bottom-up (AMF-mediated) control, an asymmetry in effects which could have precluded mutualist non-additive effects on herbivory. Further research on this, as well as other plant systems, is needed to examine the ecological contexts under which mutualist interactive effects are more or less likely to emerge and their impacts on plant fitness and associated communities.