Efficient biological nitrogen fixation (BNF) is crucial for sustainable soybean productivity. Current strategies involve the use of Bradyrhizobium diazoefficiens and co-inoculation with plant growth-promoting bacteria like Azospirillum brasilense. To further optimize BNF and plant performance, we investigated the effect of co-inoculation with A. brasilense and B. diazoefficiens combined with the strategic application of the micronutrients Molybdenum (Mo), Cobalt (Co), and Nickel (Ni) on soybean grown under greenhouse conditions. We evaluated plant growth, photosynthetic parameters, accumulation of N, nitrate reductase activity, and nifH gene expression at the R1 reproductive stage. Our main finding was that the co-inoculation combined with the simultaneous application of Mo, Co, and Ni significantly maximized vegetative growth, photochemical efficiency, and BNF. Specifically, this triple supplementation increased nifH gene expression (0.22) compared to the inoculated control (0.003), leading to a substantial enhancement of photosynthetic parameters, including photosystem II (PSII) efficiency and net carbon assimilation (A). For example, the total dry mass was 14.36 g in the Mo + Co + Ni + AZO + BRADY combination and 6.50 g in the non-inoculated and non-micronutrient-treated plants. The total N content was also higher in the plants treated with Mo + Co + Ni + AZO + BRADY (73.20 g kg⁻¹). Crucially, the data also demonstrated that excessive levels of Co impaired the symbiosis, underscoring the necessity of precise dose management. These results confirm the strong synergistic potential of combining microbial co-inoculation with targeted mineral nutrition as a high-impact, sustainable strategy for boosting soybean productivity.

The necrotrophic pathogen Sclerotinia sclerotiorum compromises the physiological and anatomical integrity of cotton, leading to substantial economic losses due to rapid tissue necrosis, stem blight, boll rot, and leaf wilting. In this context, the use of endophytic microorganisms emerges as a promising strategy for the biocontrol of white mold. This study tested the hypothesis that endophytic fungal strains isolated from the roots of Butia purpurascens, a palm tree endemic to the Cerrado biome, could mitigate disease symptoms in Gossypium hirsutum L. To evaluate this, cotton plants were subjected to biotic stress imposed by S. sclerotiorum to assess the effectiveness of seven fungal strains in attenuating disease. The impact of the pathogen was monitored through growth variables, gas exchange, leaf temperature, chlorophyll a fluorescence, antioxidant enzyme activity, proline and malondialdehyde (MDA) levels, and the incidence of rot in petioles, leaves, and flower buds. Overall, inoculation with endophytic fungi significantly alleviated the effects of the phytopathogen, promoting vegetative growth and optimizing physiological performance. Treated plants exhibited alleviated stress in primary photochemistry, reduced non-photochemical energy dissipation, and stable carbon fixation. Additionally, efficient modulation of the antioxidant system and preservation of anatomical structures were observed, minimizing the severe symptoms of white mold. Notably, the non-pathogenic strains BP10EF (Gibberella moniliformis), BP16EF (Penicillium purpurogenum), and BP33EF (Hamigera insecticola) acted as potent physiological modulators, yielding responses similar to those of healthy plants. These results highlight the biotechnological potential of these endophytic strains, which can be explored as both growth promoters and resistance inducers in cotton against white mold.

Maintaining the productivity and technological quality of sugarcane during ratoon cycles represents a constant challenge for the sugarcane-energy sector, driving the adoption of biostimulants. This study aimed to evaluate and compare the effects of different biostimulants on the biometric development, yield, and technological quality of second-ratoon sugarcane. The experiment was conducted in a randomized complete block design with four treatments and four replications: (1) Control; (2) Ascophyllum nodosum; (3) A. nodosum + nutrients; and (4) Arbuscular mycorrhizal fungus (Rhizophagus irregularis). Tiller density, stalk height, stalk diameter, stalk weight, productivity, total recoverable sugars (TRS), and sugar yield were evaluated. Data were subjected to analysis of variance (Tukey’s test, p ≤ 0.05) and principal component analysis (PCA). Tiller density was not affected by the treatments; however, biostimulation with A. nodosum alone proved to be the most effective treatment, yielding the highest stalk height (2.35 m), stalk weight (1.48 kg), TRS (146.06 kg t⁻¹), and sugar yield (14.52 t ha⁻¹), representing a 19.5% increase in sugar yield compared to the control. Inoculation with R. irregularis matched A. nodosum in productivity but resulted in lower TRS, indicating a sucrose dilution effect. A. nodosum combined with nutrients did not surpass the control across production variables. PCA confirmed the distinct separation and superiority of the isolated A. nodosum treatment along the growth and productivity axis, further demonstrating that these inputs operate through distinct physiological mechanisms. In conclusion, the A. nodosum-based biostimulant (applied alone) constitutes the most promising strategy to simultaneously enhance yield and technological quality in sugarcane ratoon crops.