Genetic and symbiotic characterization of rhizobia nodulating legumes in a mining area in southeast Brazil

Identification and selection of nitrogen-fixing bacterial strains for inoculation into native leguminous tree species can assist in the recovery of degraded areas. Additionally, native strains from these areas are genetic resources adapted to these conditions and are thus suitable for selection. The aim of this study was to symbiotically and genetically characterize 18 bacterial strains from the Rhizobium and Bradyrhizobium genera isolated from Machaerium nyctitans, Platypodium elegans, and Ormosia arborea grown in a nursery in an iron mining area. Three experiments were conducted under axenic conditions in a greenhouse. The nodulation capacity of the strains was evaluated by the number (NN) and dry matter (NDM) of nodules. Symbiotic efficiency was evaluated based on the following parameters: SPAD index (SPAD), shoot dry matter (SDM), root dry matter (RDM), and total dry matter (TDM) of the plants, relative efficiency (RE), shoot nitrogen content (SNC), and total nitrogen content in the plant (TNC). The atpD and gyrB housekeeping genes and the nifH gene were sequenced for phylogenetic analysis, and the nodC and nodD symbiotic genes of the strains were amplified. Out of the 18 strains, 16 were authenticated by nodulation capacity in the species of origin. The SPAD variable allowed for the detection of differences between treatments before the SDM. Additionally, the SPAD index showed correlation with TNC, and the strain Bradyrhizobium sp., UFLA01-839, which may represent a new species, was outstanding in Machaerium nyctitans. The nifH, nodD, and nodC genes were detected in UFLA01-839.

Genetic and symbiotic characterization of rhizobia nodulating legumes in a mining area in southeast Brazil

Identification and selection of nitrogen-fixing bacterial strains for inoculation into native leguminous tree species can assist in the recovery of degraded areas. Additionally, native strains from these areas are genetic resources adapted to these conditions and are thus suitable for selection. The aim of this study was to symbiotically and genetically characterize 18 bacterial strains from the Rhizobium and Bradyrhizobium genera isolated from Machaerium nyctitans, Platypodium elegans, and Ormosia arborea grown in a nursery in an iron mining area. Three experiments were conducted under axenic conditions in a greenhouse. The nodulation capacity of the strains was evaluated by the number (NN) and dry matter (NDM) of nodules. Symbiotic efficiency was evaluated based on the following parameters: SPAD index (SPAD), shoot dry matter (SDM), root dry matter (RDM), and total dry matter (TDM) of the plants, relative efficiency (RE), shoot nitrogen content (SNC), and total nitrogen content in the plant (TNC). The atpD and gyrB housekeeping genes and the nifH gene were sequenced for phylogenetic analysis, and the nodC and nodD symbiotic genes of the strains were amplified. Out of the 18 strains, 16 were authenticated by nodulation capacity in the species of origin. The SPAD variable allowed for the detection of differences between treatments before the SDM. Additionally, the SPAD index showed correlation with TNC, and the strain Bradyrhizobium sp., UFLA01-839, which may represent a new species, was outstanding in Machaerium nyctitans. The nifH, nodD, and nodC genes were detected in UFLA01-839.

Genetic and symbiotic characterization of rhizobia nodulating legumes in a mining area in southeast Brazil

ABSTRACT: Identification and selection of nitrogen-fixing bacterial strains for inoculation into native leguminous tree species can assist in the recovery of degraded areas. Additionally, native strains from these areas are genetic resources adapted to these conditions and are thus suitable for selection. The aim of this study was to symbiotically and genetically characterize 18 bacterial strains from the Rhizobium and Bradyrhizobium genera isolated from Machaerium nyctitans, Platypodium elegans, and Ormosia arborea grown in a nursery in an iron mining area. Three experiments were conducted under axenic conditions in a greenhouse. The nodulation capacity of the strains was evaluated by the number (NN) and dry matter (NDM) of nodules. Symbiotic efficiency was evaluated based on the following parameters: SPAD index (SPAD), shoot dry matter (SDM), root dry matter (RDM), and total dry matter (TDM) of the plants, relative efficiency (RE), shoot nitrogen content (SNC), and total nitrogen content in the plant (TNC). The atpD and gyrB housekeeping genes and the nifH gene were sequenced for phylogenetic analysis, and the nodC and nodD symbiotic genes of the strains were amplified. Out of the 18 strains, 16 were authenticated by nodulation capacity in the species of origin. The SPAD variable allowed for the detection of differences between treatments before the SDM. Additionally, the SPAD index showed correlation with TNC, and the strain Bradyrhizobium sp., UFLA01-839, which may represent a new species, was outstanding in Machaerium nyctitans. The nifH, nodD, and nodC genes were detected in UFLA01-839.

Influence of Molybdenum doses in inoculation and mineral fertilization in cowpea beans / Influência de doses de molibdênio na inoculação e na fertilização nitrogenada em feijão caupi

In some leguminous plants, associations with nitrogen-fixing microorganisms allow their nutrition with nitrogen (N) from the atmosphere. This process is known as Biological Nitrogen Fixation (BNF), where through nitrogenase enzymes, N2 is converted to an available form. This process can replace in part, or in total, nitrogen fertilizers. Cowpea bean is a legume species that is recognized for its high capacity to carry out BNF. In the last decades, studies have encouraged small farmers from north and northeast Brazil to use inoculants with rhizobia species since the results of researches have demonstrated that inoculation is an interesting strategy to improve cowpea production. Considering the specific function of molybdenum (Mo) in the N assimilation, different doses of Mo were tested in this study in order to find doses that could improve and enhance BNF. Therefore, this study aimed to compare nitrogen fertilization and BNF in the N assimilation by plants with different Mo doses. Inoculation was performed with the strains UFLA 03-84 and INPA 03-11B. Doses of Mo were applied in seeds and each pot contained five seeds. Thirty-five days after germination, the plants were analyzed for shoot dry matter and fresh matter, N contents and accumulation, as well as the Soil-Plant Analysis Development (SPAD) Index and nodulation in inoculated plants. The different doses of Mo and also the nodulation treatments did not show significant differences in the contents of N. Plants with N fertilization had significant higher shoot dry matter and root dry matter production, in addition to higher N foliar contents and N accumulation. Therefore, BNF was not as efficient as nitrogen fertilization in the evaluated experimental conditions using cowpea beans.

Em algumas plantas de leguminosas, as associações com microorganismos de fixação permitem a sua nutrição com N (nitrogênio) da atmosfera. Este processo é conhecido como Fixação Biológica de Nitrogênio (FBN), onde através de enzimas nitrogenase N2 é convertido na forma disponível. Este processo pode substituir em parte, ou no total, fertilizantes nitrogenados. O feijão-caupi é uma espécie de leguminosa que é reconhecida pela sua alta capacidade de FBN. Nas últimas décadas, estudos encorajaram os pequenos agricultores do norte e nordeste do Brasil a usar inoculantes com espécies de rizobio, uma vez que os resultados das pesquisas têm demonstrado que a inoculação é uma estratégia interessante para melhorar a produção dessa cultura. Considerando a função específica do molibdênio (Mo) na assimilação do N, diferentes doses de Mo foram testadas neste estudo, a fim de encontrar doses que possam melhorar e potencializar a FBN. A inoculação foi feita com as estirpes UFLA 03-84 e INPA 03-11B. As diferentes doses de Mo foram aplicadas na semente, cinco sementes por vaso. Trinta e cinco dias após a germinação, as plantas foram analisadas com relação à matéria seca aérea e radicular, teor de N e acúmulo, índice de análise de desenvolvimento solo-planta (SPAD) e nodulação nas plantas inoculadas. As diferentes doses de Mo não mostraram diferenças significativas no conteúdo de N, nem no processo de nodulação. As plantas com adubação nitrogenada tiveram mattera seca da parte aérea e de raízes superior as inoculadas, além de maiores teores foliares de N. Portanto, para feijão-caupi, a FBN não foi tão eficiente quanto o fertilizante nitrogenado nas condições experimentais avaliadas.