This study investigates the role of arbuscular mycorrhizal fungi (AMF) in the metabolism of hexabromocyclododecane (HBCD) and its ecological effects in contaminated environments. We focused on the symbiotic relationships between Iris pseudacorus L. and AMF (Rhizophagus irregularis) under HBCD exposure. Our results show that HBCD induces oxidative damage, which hinders plant growth. However, AMF significantly enhance the plant's antioxidant defenses, reducing oxidative damage and supporting better growth of I. pseudacorus. HBCD biodegradation patterns showed beta- > gamma- > alpha-HBCD, with AMF playing a key role in stabilizing rhizosphere microbial communities, particularly promoting Proteobacteria and potential bacterial degraders like Aeromonas and Trichococcus, which contributed to HBCD removal. Additionally, AMF appear to upregulate genes such as cypD_E, GST, dehH, dehA, dehM, Em3.8.1.2, and ligB, which are involved in debromination and hydroxylation reactions. This research highlights AMF's potential to enhance the phytoremediation of HBCD, providing valuable insights for environmental remediation strategies.

Large amounts of chemical fertilizers are still used to suppress pathogens and boost agricultural productivity and food generation. However, their use can cause harmful environmental imbalance. Furthermore, plants typically absorb limited amounts of the nutrients provided by chemical fertilizers. Recent studies are recommending the use of microbiota present in the soil in different formulations, considering that several microorganisms are found in nature in association with plants in a symbiotic, antagonistic, or synergistic way. This ecological alternative is positive because no undesirable significant alterations occur in the environment while stimulating plant nutrition development and protection against damage caused by control pathogens. Therefore, this review presents a comprehensive discussion regarding endophytic and rhizospheric microorganisms and their interaction with plants, including signaling and bio-control processes concerning the plant's defense against pathogenic spread. A discussion is provided about the importance of these bioinputs as a microbial resource that promotes plant development and their sustainable protection methods aiming to increase resilience in the agricultural system. In modern agriculture, the manipulation of bioinputs through Rhizobium contributes to reducing the effects of greenhouse gases by managing nitrogen runoff and decreasing nitrous oxide. Additionally, mycorrhizal fungi extend their root systems, providing plants with greater access to water and nutrients.

Walnut (Juglans regiaL.), an important economic forest worldwide, grows in mountainous areas prone to soil drought, which reduces its growth and yield. This study aimed to analyze whether Serendipita indica, a culturable endophytic fungus, colonizes walnut roots, hence improving walnut growth and resistance to drought stress. A high density of chlamydospores was observed within the cortical cells of S. indica-colonized roots, with root colonization ranged from 58.3 to 79.1%, as well as a significant inhibition under drought versus non-drought. Drought treatment suppressed aboveground performance and root morphology variables, while S. indica significantly boosted them. Inoculation with S. indica also significantly increased leaf nitrogen balance index and betaine levels under drought. In leaf mitochondria, drought treatment led to increased levels of hydrogen peroxide (H2O2) and superoxide anion radicals (O-2(center dot-)), with greater increases observed in uninoculated plants than in inoculated plants. However, inoculation with S. indica significantly decreased H2O2 and O-2(center dot-) levels in walnut leaves, with inoculated plants experiencing a greater substantial decrease than uninoculated plants. Drought treatment and S. indica collectively significantly increased leaf superoxide dismutase and catalase activities in mitochondria, allowing inoculated plants to maintain low oxidative damage by decreasing malondialdehyde levels. S. indica also boosted leaf juglone levels by promoting beta-glucosidase activity under drought conditions. In conclusion, S. indica is a helpful endophytic fungus for increasing walnut growth and tolerance to drought by activating antioxidant defenses in mitochondria, which presents a promising pathway for sustainable agroforestry practices.

The application of rhizobia-legume symbioses is a sustainable approach to alleviate water stress and restore damaged areas. In this context, three strains Bradyrhizobium sp. BA2, RDI18 and RDT46 previously isolated from root nodules of Retama dasycarpa grown in the Moroccan High Atlas Mountains, were selected to investigate their prominent drought-tolerance capacity and significant plant growth-promoting (PGP) traits under drought stress. Subsequently, we analyzed the impact of individual or combined inoculations by the three strains on R. dasycarpa responses to three water regimes (40, 70, and 100 field capacity). The three strains tolerate different concentrations of PEG 6000 and possess different PGP activities, including phosphate solubilization, production of siderophore, exopolysaccharides, and auxin, under osmotic stress. The inoculation had a positive impact on plant response under all applied water regimes as it improved shoot and root length biomass, and chlorophyll content. The water stress reduced shoot length and dry weight of all plants. However, the inoculated plants maintained the highest values. The water stress reduced the infectivity of strains BA2 and RDI18, but not strain RDT46, which is not competitive at any water regime. Furthermore, water stress had no effect on the three strains' symbiotic efficiency, whereas it increased considerably the efficiency index of strains BA2 and RDI18. Proline and protein content increased in non-inoculated plants; whereas the inoculation significantly increased the catalase activity in plants under 40 % FC. These results show that the inoculation with appropriate strains such as BA2 and RDI18, enhance plant resilience to drought season.

Both sulfur (S) supply and legume-rhizobium symbiosis can significantly contribute to enhancing the efficiency of phytoremediation of heavy metals (HMs). However, the regulatory mechanism determining the performance of legumes at lead (Pb) exposure have not been elucidated. Here, we cultivated black locust ( Robinia pseudoacacia L.), a leguminous woody pioneer species at three S supply levels ( i.e., deficient, moderate, and high S) with rhizobia inoculation and investigated the interaction of these treatments upon Pb exposure. Our results revealed that the root system of Robinia has a strong Pb accumulation and anti-oxidative capacity that protect the leaves from Pb toxicity. Compared with moderate S supply, high S supply significantly increased Pb accumulation in roots by promoting the synthesis of reduced S compounds ( i.e., thiols, phytochelatin), and also strengthened the antioxidant system in leaves. Weakened defense at deficient S supply was indicated by enhanced oxidative damage. Rhizobia inoculation alleviated the oxidative damage of its Robinia host by immobilizing Pb to reduce its absorption by root cells. Together with enhanced Pb chelation in leaves, these mechanisms strengthen Pb detoxification in the Robinia-rhizobia symbiosis. Our results indicate that appropriate S supply can improve the defense of legume-rhizobia symbiosis against HM toxicity.

Soil nitrogen is crucial for agriculture, but it is often limited, affecting crop yields. Deficiency requires synthetic fertilizers, but their improper use results in environmental damage and high costs. Bacteria of the genus Rhizobium , symbionts of legumes, offer a sustainable solution by fixing nitrogen, thus reducing dependence on fertilizers. This research determined the most probable number (MPN) of cells of Rhizobium spp. from two commercial biofertilizers of Ecuadorian and Mexican origin under greenhouse conditions. For this, direct inoculation with serial dilutions (10(-1) to 10(-10) ) was performed in pots with steam -sterilized pumice where Blue Lake variety snap bean ( Phaseolus vulgaris L.) plants were germinated. The following morphological indicators were evaluated at 45 days after sowing (DAS): leaf area, plant wet weight, plant height, and number of flowers, determining statistical differences between the type of biofertilizer and the concentration of each dilution. The experiment followed a randomized complete block design with a split -plot arrangement, with three replicates per dilution, considering temperature fluctuations in the study area. The MPN at 95% confidence was 4.45x10(7) rhizobia g -1 of pumice at a 10(-5) dilution for the Mexican biofertilizer, and 1.48x10(5) rhizobia g(-1) of pumice at a 10(-4) dilution for the Ecuadorian biofertilizer. The estimated optimal dilution for both products was 10(-8).