The mung bean has a great potential under tropical conditions given its high content of grain protein. Additionally, its ability to benefit from biological nitrogen fixation (BNF) through association with native rhizobia inhabiting nodule microbiome provides most of the nitrogen independence on fertilizers. Soil microbial communities which are influenced by biogeographical factors and soil properties, represent a source of rhizobacteria capable of stimulating plant growth. The objective of this study is to support selection of beneficial bacteria that form positive interactions with mung bean plants cultivated in tropical soils, as part of a seed inoculation program for increasing grain yield based on the BNF and other mechanisms. Two mung bean genotypes (Camaleão and Esmeralda) were cultivated in 10 soil samples. Nodule microbiome was characterized by next-generation sequencing using Illumina MiSeq 16S rRNA. More than 99% of nodule sequences showed similarity with Bradyrhizobium genus, the only rhizobial present in nodules in our study. Higher bacterial diversity of soil samples collected in agribusiness areas (MW_MT-I, II or III) was associated with Esmeralda genotype, while an organic agroecosystem soil sample (SE_RJ-V) showed the highest bacterial diversity independent of genotype. Furthermore, OTUs close to Bradyrhizobium elkanii have dominated in all soil samples, except in the sample from the organic agroecosystem, where just B. japonicum was present. Bacterial community of mung bean nodules is mainly influenced by soil pH, K, Ca, and P. Besides a difference on nodule colonization by OTU sequences close to the Pseudomonas genus regarding the two genotypes was detected too. Although representing a small rate, around 0.1% of the total, Pseudomonas OTUs were only retrieved from nodules of Esmeralda genotype, suggesting a different trait regarding specificity between macro- and micro-symbionts. The microbiome analysis will guide the next steps in the development of an inoculant for mung bean aiming to promote plant growth and grain yield, composed either by an efficient Bradyrhizobium strain on its own or co-inoculated with a Pseudomonas strain. Considering the results achieved, the assessment of microbial ecology parameters is a potent coadjuvant capable to accelerate the inoculant development process and to improve the benefits to the crop by soil microorganisms.

Pulses provide distinct health benefits due to their low fat content and high protein and fiber contents. Their grain production reaches approximately 93,210 × 10³ tons per year. Pulses benefit from the symbiosis with atmospheric N₂-fixing bacteria, which increases productivity and reduces the need for N fertilizers, thus contributing to mitigation of environmental impact mitigation. Additionally, the root region harbors a rich microbial community with multiple traits related to plant growth promotion, such as nutrient increase and tolerance enhancement to abiotic or biotic stresses. We reviewed the eight most common pulses accounting for almost 90% of world production: common beans, chickpeas, peas, cowpeas, mung beans, lentils, broad beans, and pigeon peas. We focused on updated information considering both single-rhizobial inoculation and co-inoculation with plant growth-promoting rhizobacteria. We found approximately 80 microbial taxa with PGPR traits, mainly Bacillus sp., B. subtilis, Pseudomonas sp., P. fluorescens, and arbuscular mycorrhizal fungi, and that contributed to improve plant growth and yield under different conditions. In addition, new data on root, nodule, rhizosphere, and seed microbiomes point to strategies that can be used to design new generations of biofertilizers, highlighting the importance of microorganisms for productive pulse systems.

O objetivo deste trabalho foi avaliar a produção e o comportamento reológico de exopolissacarídeos (EPS) produzidos por rizóbios isolados de nódulos de guandu [Cajanus cajan (L.) Millsp.], e a similaridade desses isolados, pela técnica de análise de restrição do DNA ribossomal amplificado. As bactérias foram cultivadas em meio YM líquido e os EPS foram obtidos por precipitação com etanol gelado a partir do caldo de cultivo. Em seguida, eles foram recuperados por centrifugação, secados a vácuo, pesados e ressuspensos em água para avaliações reológicas. Os três isolados avaliados apresentaram diferenças na produção e na eficiência relativa da produção de EPS, com destaque para o isolado 8.1c. Os EPS demonstraram comportamento não newtoniano e pseudoplástico, porém também apresentaram diferenças na viscosidade aparente em uma mesma taxa de cisalhamento. Na taxa de cisalhamento de 1 s-1, os três isolados foram diferentes, enquanto na taxa de cisalhamento de 40 s-1, os isolados 53.5 e 30.6a2 foram iguais e diferiram do isolado 8.1c. A similaridade dos isolados foi condizente com os resultados de reologia dos EPS, em que bactérias que sintetizaram EPS com menor viscosidade aparente apresentaram maior similaridade

The objective of this work was to evaluate the response of the BRS Tumucumaque cowpea (Vigna unguiculata) cultivar to liming and to phosphorus and potassium fertilization in the absence of inoculation or nitrogen fertilization, as well as to inoculation with selected Bradyrhizobium strains, in an upland forest area in the state of Amapá, eastern Amazon, Brazil. Seven experiments were conducted in field conditions, in order to evaluate six limestone, four phosphorus, and four potassium rates, besides the inoculation with four Bradyrhizobium strains. Leaf nitrogen concentrations, pod and grain dry mass per plant, grain yield, and soil pH, Al+3, and Ca+2 + Mg+2 were evaluated. The obtained data were subjected to the analysis of variance, to the regression analysis, or to test to compare means. The soil presented a high buffer power, but liming reduced its chemical limitations. Leaf nitrogen concentrations were correlated to cowpea grain yield. However, there is no effect of the interaction between potassium and phosphorus rates on grain yield. In addition, grain yield is not influenced by liming and potassium fertilization, but is increased by phosphorus fertilization. Inoculation with the UFLA 3-84 and INPA 03-11B strains promotes a greater grain yield than that with BR 3262 and BR 3267, as well as a similar grain yield to that of the control without inoculation.