Co-inoculation of Anabaena cylindrica and Azospirillum brasilense during initial growth and chloroplast pigments of corn

ABSTRACT Although the isolated effects of the cyanobacteria Anabaena cylindrica and the bacteria Azospirillum brasilense are well-known, the co-inoculation of both can promote other benefits to corn plants’ biological nitrogen fixation and growth. The aim was to evaluate the initial growth and chloroplast pigment levels of corn hybrids co-inoculated with A. brasilense and A. cylindrica. The experiment was conducted in greenhouse conditions using the completely randomized design in a factorial scheme 2 × 4 with two hybrids, Balu 184 and Balu 280 Pro, and four inoculation treatments: no inoculation, inoculation of A. cylindrica, inoculation of A. brasilense, and the co-inoculation of A. cylindrica + A. brasilense. Co-inoculation resulted in higher root growth and dry mass of the aerial part in both hybrids; however, the hybrid Balu 280 Pro presented higher responsivity. The co-inoculation of A. brasilense and A. cylindrica increased initial corn growth without altering the photosynthetic pigment levels.

Correlations and Path Analysis in Segregating Cowpea Generations Regarding Biological Nitrogen Fixation

The objective of this research was to evaluate the correlations between variables related to the biological nitrogen fixation (BNF) in segregating generations of cowpea and to unfold these correlations in direct and indirect effects, through path analysis. An outdoor bench experiment was conducted at Carpina Experimental Sugarcane Station of, located at the Zona da Mata region of the State of the Pernambuco, Northeast of Brazil (Federal Rural University of Pernambuco), between March and April 2016. The seeds were planted in 20 cm × 30 cm polyethylene bags, using a substrate composed of a mixture of vermiculite and sand washed in a ratio of 1:1. Bradyrhizobium references, recommended for culture, were used as a mixture of two strains. Parental and F2, F3 and F4 generations were evaluated in a randomized block design with four replicates. Data collection was performed 45 days after the emergency (DAE). Phenotypic correlations and path analysis of the number of nodules per plant (NN), nodules dry mass (NDM), dry roots mass (DRM), dry mass of aerial part (DMAP), nodulation efficiency (NODE) and nitrogen accumulated in the aerial part (NAAP). The phenotypic correlations between the variables related to the BNF showed high magnitudes, demonstrating that there is a great influence of each of the variables on the others, furthermore the path analysis of the coefficients indicated that all the primary components (NN, NDM, DRM, DMAP and NODE) must be considered when it is desired to increase the NAAP in segregating generations of cowpea.

Nitrogen Acquisition Strategies Mediated by Insect Symbionts: A Review of Their Mechanisms, Methodologies, and Case Studies

Nitrogen is usually a restrictive nutrient that affects the growth and development of insects, especially of those living in low nitrogen nutrient niches. In response to the low nitrogen stress, insects have gradually developed symbiont-based stress response strategies—biological nitrogen fixation and nitrogenous waste recycling—to optimize dietary nitrogen intake. Based on the above two patterns, atmospheric nitrogen or nitrogenous waste (e.g., uric acid, urea) is converted into ammonia, which in turn is incorporated into the organism via the glutamine synthetase and glutamate synthase pathways. This review summarized the reaction mechanisms, conventional research methods and the various applications of biological nitrogen fixation and nitrogenous waste recycling strategies. Further, we compared the bio-reaction characteristics and conditions of two strategies, then proposed a model for nitrogen provisioning based on different strategies.

Enhanced Soybean Productivity by Inoculation With Indigenous Bradyrhizobium Strains in Agroecological Conditions of Northeast Germany

Commercial inoculants are often used to inoculate field-grown soybean in Europe. However, nodulation efficiencies in these areas are often low. To enhance biological nitrogen (N) fixation and increase domestic legume production, indigenous strains that are adapted to local conditions could be used to develop more effective inoculants. The objective of this study was to assess the ability of locally isolated Bradyrhizobium strains to enhance soybean productivity in different growing conditions of Northeast Germany. Three indigenous Bradyrhizobium isolates (GMF14, GMM36, and GEM96) were tested in combination with different soybean cultivars of different maturity groups and quality characteristics in one field trial and two greenhouse studies. The results showed a highly significant strain × cultivar interactions on nodulation response. Independent of the Bradyrhizobium strain, inoculated plants in the greenhouse showed higher nodulation, which corresponded with an increased N uptake than that in field conditions. There were significantly higher nodule numbers and nodule dry weights following GMF14 and GMM36 inoculation in well-watered soil, but only minor differences under drought conditions. Inoculation of the soybean cultivar Merlin with the strain GEM96 enhanced nodulation but did not correspond to an increased grain yield under field conditions. USDA110 was consistent in improving the grain yield of soybean cultivars Sultana and Siroca. On the other hand, GMM36 inoculation to Sultana and GEM96 inoculation to Siroca resulted in similar yields. Our results demonstrate that inoculation of locally adapted soybean cultivars with the indigenous isolates improves nodulation and yield attributes. Thus, to attain optimal symbiotic performance, the strains need to be matched with specific cultivars.

Evaluating fixed-film nitrification systems in autotrophic mode: Enhanced biomass retention does not improve bioreactor performance during alkalinity induced stress

Use of fixed-film systems has shown promise towards improving the process stability of biological nitrogen removal (BNR). It allows for biofilm formation, which can offer enhanced resilience to environmental stressors...

Potential of Phototrophic Purple Nonsulfur Bacteria to Fix Nitrogen in Rice Fields

Biological nitrogen fixation catalyzed by Mo-nitrogenase of symbiotic diazotrophs has attracted interest because its potential to supply plant-available nitrogen offers an alternative way of using chemical fertilizers for sustainable agriculture. Phototrophic purple nonsulfur bacteria (PNSB) diazotrophically grow under light anaerobic conditions and can be isolated from photic and microaerobic zones of rice fields. Therefore, PNSB as asymbiotic diazotrophs contribute to nitrogen fixation in rice fields. An attempt to measure nitrogen in the oxidized surface layer of paddy soil estimates that approximately 6–8 kg N/ha/year might be accumulated by phototrophic microorganisms. Species of PNSB possess one of or both alternative nitrogenases, V-nitrogenase and Fe-nitrogenase, which are found in asymbiotic diazotrophs, in addition to Mo-nitrogenase. The regulatory networks control nitrogenase activity in response to ammonium, molecular oxygen, and light irradiation. Laboratory and field studies have revealed effectiveness of PNSB inoculation to rice cultures on increases of nitrogen gain, plant growth, and/or grain yield. In this review, properties of the nitrogenase isozymes and regulation of nitrogenase activities in PNSB are described, and research challenges and potential of PNSB inoculation to rice cultures are discussed from a viewpoint of their applications as nitrogen biofertilizer.