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Studies have shown that the application of arbuscular mycorrhizal (AM) fungi or exogenous melatonin (MT) can alleviate drought stress and improve plant growth, but the additive effects of both treatments on plants grown under drought stress are largely unknown. In this study, we conducted a pot experiment to investigate the effects of AM inoculation (Funneliformis mosseae BGC XJ01) and/or MT application on tobacco (Nicotiana tabacum L. cv. Yuyan No. 6) seedling growth, photosynthetic and chlorophyll fluorescence parameters, antioxidant enzymatic activity, osmotic adjustment substance accumulation, and nutrient uptake under three water conditions (75–80%, 50–55%, and 30–35% of the maximum moisture retention capacity). The results show that applying either the AM inoculant or MT alone significantly increased tobacco seedling growth and decreased the negative effects of drought stress. Furthermore, AM inoculation alone promoted root function (root biomass, root/shoot ratio, root system architecture), facilitated the capture and conversion of solar energy (photosynthetic rate, ΦPSII), and increased nutrient uptake more effectively than MT. In contrast, exogenous MT application alone was more effective at increasing peroxidase and catalase activity and decreasing H2O2 and MDA accumulation, which in turn enhanced the adaptation of seedlings to drought stress by improving their antioxidant capacity and reducing oxidative damage. Nevertheless, applying exogenous MT significantly enhanced the AM colonization rate under AM inoculation conditions but had no obvious effect on AM colonization under noninoculated conditions. The combined application of AM and MT had an additive effect and produced the largest increases in tobacco seedling growth, photosynthetic ability, antioxidant enzymatic activity, and N, P, and K uptake and the largest decreases in H2O2 and MDA contents of all the treatments. The results suggest that AM inoculation in combination with exogenous MT application may render plants more productive and more tolerant of drought stress.

Arbuscular mycorrhizal fungi (AMF) are considered as a potential biotechnological tool for improving phytostabilization efficiency and plant tolerance to heavy metal-contaminated soils. However, the mechanisms through which AMF help to alleviate metal toxicity in plants are still poorly understood. A greenhouse experiment was conducted to evaluate the effects of two AMF species (Funneliformis mosseae and Rhizophagus intraradices) on the growth, Pb accumulation, photosynthesis and antioxidant enzyme activities of a leguminous tree (Robinia pseudoacacia L.) at Pb addition levels of 0, 500, 1000 and 2000 mg kg(-1) soil. AMF symbiosis decreased Pb concentrations in the leaves and promoted the accumulation of biomass as well as photosynthetic pigment contents. Mycorrhizal plants had higher gas exchange capacity, non-photochemistry efficiency, and photochemistry efficiency compared with non-mycorrhizal plants. The enzymatic activities of superoxide dismutase (SOD), ascorbate peroxidases (APX) and glutathione peroxidase (GPX) were enhanced, and hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents were reduced in mycorrhizal plants. These findings suggested that AMF symbiosis could protect plants by alleviating cellular oxidative damage in response to Pb stress. Furthermore, mycorrhizal dependency on plants increased with increasing Pb stress levels, indicating that AMF inoculation likely played a more important role in plant Pb tolerance in heavily contaminated soils. Overall, both F. mosseae and R. intraradices were able to maintain efficient symbiosis with R. pseudoacacia in Pb polluted soils. AMF symbiosis can improve photosynthesis and reactive oxygen species (ROS) scavenging capabilities and decrease Pb concentrations in leaves to alleviate Pb toxicity in R. pseudoacacia. Our results suggest that the application of the two AMF species associated with R. pseudoacacia could be a promising strategy for enhancing the phytostabilization efficiency of Pb contaminated soils.

BackgroundArbuscular mycorrhizal (AM) fungi form symbiotic associations with roots in most land plants. AM symbiosis provides benefits to host plants by improving nutrition and fitness. AM symbiosis has also been associated with increased resistance to pathogen infection in several plant species. In rice, the effects of AM symbiosis is less studied, probably because rice is mostly cultivated in wetland areas, and plants in such ecosystems have traditionally been considered as non-mycorrhizal. In this study, we investigated the effect of AM inoculation on performance of elite rice cultivars (Oryza sativa, japonica subspecies) under greenhouse and field conditions, focusing on growth, resistance to the rice blast fungus Magnaporthe oryzae and productivity.ResultsThe response to inoculation with either Funneliformis mosseae or Rhizophagus irregularis was evaluated in a panel of 12 rice cultivars. Root colonization was confirmed in all rice varieties. Under controlled greenhouse conditions, R. irregularis showed higher levels of root colonization than F. mosseae. Compared to non-inoculated plants, the AM-inoculated plants had higher Pi content in leaves. Varietal differences were observed in the growth response of rice cultivars to inoculation with an AM fungus, which were also dependent on the identity of the fungus. Thus, positive, negligible, and negative responses to AM inoculation were observed among rice varieties. Inoculation with F. mosseae or R. irregularis also conferred protection to the rice blast fungus, but the level of mycorrhiza-induced blast resistance varied among host genotypes. Rice seedlings (Loto and Gines varieties) were pre-inoculated with R. irregularis, transplanted into flooded fields, and grown until maturity. A significant increase in grain yield was observed in mycorrhizal plants compared with non-mycorrhizal plants, which was related to an increase in the number of panicles.ConclusionResults here presented support that rice plants benefit from the AM symbiosis while illustrating the potential of using AM fungi to improve productivity and blast resistance in cultivated rice. Differences observed in the mycorrhizal responsiveness among the different rice cultivars in terms of growth promotion and blast resistance indicate that evaluation of benefits received by the AM symbiosis needs to be carefully evaluated on a case-by-case basis for efficient exploitation of AM fungi in rice cultivation.

Arbuscular mycorrhizal fungi (AMF) can enhance drought tolerance in plants, whereas little is known regarding AMF contribution to sucrose and proline metabolisms under drought stress (DS). In this study, Funneliformis mosseae and Paraglomus occultum were inoculated into trifoliate orange ( Poncirus trifoliata ) under well watered and DS. Although the 71-days DS notably ( P  < 0.05) inhibited mycorrhizal colonization, AMF seedlings showed significantly ( P  < 0.05) higher plant growth performance and leaf relative water content, regardless of soil water status. AMF inoculation significantly ( P  < 0.05) increased leaf sucrose, glucose and fructose concentration under DS, accompanied with a significant increase of leaf sucrose phosphate synthase, neutral invertase, and net activity of sucrose-metabolized enzymes and a decrease in leaf acid invertase and sucrose synthase activity. AMF inoculation produced no change in leaf ornithine-δ-aminotransferase activity, but significantly ( P  < 0.05) increased leaf proline dehydrogenase activity and significantly ( P  < 0.05) decreased leaf both Δ 1 -pyrroline-5-carboxylate reductase and Δ 1 -pyrroline-5-carboxylate synthetase activity, resulting in lower proline accumulation in AMF plants under DS. Our results therefore suggest that AMF strongly altered leaf sucrose and proline metabolism through regulating sucrose- and proline-metabolized enzyme activities, which is important for osmotic adjustment of the host plant.

The study aimed to find the best Arbuscular Mycorrhizal Fungi (AMF) strain for cotton growth in Xinjiang's salinity and alkali conditions. Cotton (Xinluzao 45) was treated with Funneliformis mosseae (GM), Rhizophagus irregularis (GI), and Claroideoglomus etunicatum (GE) as treatments, while untreated cotton served as the control (CK). Salinity stress was applied post-3-leaf stage in cotton. The study analyzed cotton's reactions to diverse saline-alkali stresses, focusing on nutrient processes and metabolism. By analyzing the growth and photosynthetic characteristics of plants inoculated with Funneliformis mosseae to evaluate its salt tolerance. Saline-alkali stress reduced chlorophyll and hindered photosynthesis, hampering cotton growth. However, AMF inoculation mitigated these effects, enhancing photosynthetic rates, CO 2 concentration, transpiration, energy use efficiency, and overall cotton growth under similar stress levels. GM and GE treatments yielded similar positive effects. AMF inoculation enhanced cotton plant height and biomass. In GM treatment, cotton exhibited notably higher root length than other treatments, showing superior growth under various conditions. In summary, GM-treated cotton had the highest infection rate, followed by GE-treated cotton, with GI-treated cotton having the lowest rate (GM averaging 0.95). Cotton inoculated with Funneliformis mosseae, Rhizophagus irregularis, and Claroideoglomus etunicatum juvenile showed enhanced chlorophyll and photosynthetic levels, reducing salinity effects. Funneliformis mosseae had the most significant positive impact.

Fitness of plants is affected by their symbiotic interactions with arbuscular mycorrhizal fungi (AMF), and such effects are highly dependent on the environmental context. In the current study, we inoculated the nursery shrub species with AMF species under contrasting levels of soil water and nutrients (diammonium phosphate fertilization), to assess their effects on plant growth, physiology and natural infestation by herbivores. Overall, plant biomass was synergistically enhanced by increasing soil water and soil nutrient levels. However, plant height was surprisingly repressed by AMF inoculation, but only under low water conditions. Similarly, plant biomass was also reduced by AMF but only under low water and nutrient conditions. Furthermore, AMF significantly reduced leaf phosphorus levels, that were strongly enhanced under high nutrient conditions, but had only minor effects on leaf chlorophyll and proline levels. Under low water and nutrient conditions, specific root length was enhanced, but average root diameter was decreased by AMF inoculation. The negative effects of AMF on plant growth at low water and nutrient levels may indicate that under these conditions AMF inoculation does not strongly contribute to nutrient and water acquisition. On the contrary, the AMF might have suppressed the direct pathway of water and nutrient absorption by the plant roots themselves despite low levels of mycorrhizal colonization. AMF inoculation reduced the abundance of the foliar herbivore on plants that had been grown on the low nutrient soil, but not on high nutrient soil. Fertilization enhanced the abundance of this herbivore but only in plants that had received the high water treatment. The lower abundance of the herbivore on AMF plants could be related to their decreased leaf P content. In conclusion, our results indicate that AMF negatively affect the growth of but makes them less attractive to a dominant herbivore. Our study highlights that plant responses to AMF depend not only on the environmental context, but that the direction of the responses can differ for different components of plant performance (growth vs. defense).

To test direct and indirect effects of glomalin, mycorrhizal hyphae and roots on aggregate stability, perspex pots separated by 37-μm nylon mesh in the middle were used to form root-free hyphae and root/hyphae chambers, where trifoliate orange ( Poncirus trifoliata ) seedlings were colonized by Funneliformis mosseae or Paraglomus occultum in the root/hyphae chamber. Both fungal species induced significantly higher plant growth, root total length, easily-extractable glomalin-related soil protein (EE-GRSP) and total GRSP (T-GRSP) and mean weight diameter (an aggregate stability indicator). The Pearson correlation showed that root colonization or soil hyphal length significantly positively correlated with EE-GRSP, difficultly-extractable GRSP (DE-GRSP), T-GRSP and water-stable aggregates in 2.00–4.00, 0.50–1.00 and 0.25–0.50 mm size fractions. The path analysis indicated that in the root/hyphae chamber, aggregate stability derived from a direct effect of root colonization, EE-GRSP or DE-GRSP. Meanwhile, the direct effect was stronger by EE-GRSP or DE-GRSP than by mycorrhizal colonization. In the root-free hyphae chamber, mycorrhizal-mediated aggregate stability was due to total effect but not direct effect of soil hyphal length, EE-GRSP and T-GRSP. Our results suggest that GRSP among these tested factors may be the primary contributor to aggregate stability in the citrus rhizosphere.

PurposeThis study was to investigate the regulation of sulfur status in continuous-cropping soybean soil by Funneliformis mosseae and Thiobacillus thioparus and promote the absorption of sulfur in soybean. To explore the interactions among F. mosseae, T. thioparus and soybean plants, this study laid a theoretical foundation for the application of F. mosseae and T. thioparus as biological agents in agricultural production.MethodsPot culture, a two-compartment system and shake-flask culture were used in the experiment. Using F. mosseae and T. thioparus as experimental inoculants, the effects of F. mosseae on sulfur oxide of T. thioparus and their interaction on the growth of soybean plants were studied from the aspects of soil sulfur content, sulfur functional genes and the growth of soybean and sulfur-oxidizing bacteria.ResultsThe F. mosseae and T. thioparus inoculation significantly increased the abundance of sulfur-oxidizing bacteria and available sulfur content in the soil, stimulated the expression of sulfate transporter genes in soybean roots, and promoted the absorption of sulfur nutrients in soybean. F. mosseae stimulated the expression of the T. thioparus sulfur-oxidation gene and enhanced the sulfur-oxidation capacity, while T. thioparus enhanced F. mosseae colonization of soybean roots. Thus, F. mosseae and T. thioparus promoted soil sulfur cycling and sulfate transport in soybean roots, which proved that F. mosseae could effectively improve the sulfur-oxidation capacity of T. thioparus.ConclusionDouble inoculation with F. mosseae and T. thioparus significantly promoted soybean plant growth and increased soil sulfur utilization.

The effects of three biological control agents (BCAs) including Funneliformis mosseae BEG12 (FM) as arbuscular mycorrhizal fungi (AMF), Bacillus velezensis V40K2 (BV) as plant growth-promoter rhizobacterium (PGPR) and Trichoderma viride NTC2 (TV) as plant growth-promoter fungus (PGPF) against Alternaria solani (Ellis & Martin) Sorauer (AS) were studied. For this purpose, 2.5 g FM (150 spores g −1 ) was inoculated in the seed bed. After seedling emergence, TV (1 × 10 6 spor/ml) as well as BV (1 × 10 8  CFU mL −1 ) were inoculated. Then, onee week after TV and BV treatments, 1 × 10 6 spore mL −1 of AS was inoculated by spraying on each plant. It was found that the single, double and triple combinations of these selected biocontrol agents against pathogen generally suppressed the disease severity and stimulated the plant growth. Compared to other treatments without any positive effects, the use of the AM fungal treatment had positive effects on the total phenolic content as well as antioxidant activity. Also, the highest total phosphorus content was observed in FM + TV + AS (7.3%) and AS (8.0%) treatments. No statistically significant difference was observed among the combinations in terms of the AMF colonization rate and soil spore density, which showing that mycorrhizal dependency did not occur in the FM + TV + BV + AS treatment (-6.7). However, compared to the control group, this treatment did not affect on disease suppression and plant growth parameters.

The Arbuscular mycorrhizal fungi (AMF) (Funneliformis mosseae), are the most widely distributed symbiont assisting plants to overcome counteractive environmental conditions. In order to improve the sustainability and the activity of AMF, the use of nanotechnology was important. The main objective of this study was to investigate the effect of titanium dioxide nanoparticles (TiO.sub.2 NPs) on the activity of AMF in common bean roots as well as its activity under salinity stress using morphological and molecular methods. The activity of AMF colonization has increased in the presence of TiO.sub.2 NPs especially for arbuscule activity (A%), which increased three times with the presence of TiO.sub.2 NPs. The improvement rate of Funneliformis mosseae on plant growth increased from 180% to 224% of control at the lowest level of salinity and increased from 48% to 130% at higher salinity level, respectively. The AMF dependencies for plant dry biomass increased in the presence of TiO.sub.2 NPs from 277% in the absence of salinity to 465 and 883% % at low and high salinity levels, respectively. The presence of AMF co-inoculated with TiO.sub.2 NPs resulted in increasing the salinity tolerance of plants at all levels and reached 110% at salinity level of 100 mM NaCl. Quantitative colonization methods showed that the molecular intensity ratio and the relative density of paired inocula AMF Nest (NS) or chitin synthases gene (Chs) with TiO.sub.2 NPs were higher significantly P.>0.05 than single inoculants of AMF gene in roots under the presence or the absence of salinity by about two folds and about 40%. Hence, the positive effect of TiO.sub.2 NPs was confined to its effect on AMF not on bean plants itself.