This study evaluated 26 pigeonpea rhizobial isolates according to their cultural characteristics, intrinsic antibiotic resistance, salt and temperature tolerance, carbon source utilization and amylolytic activity. The cultural characterization showed that the majority of them presented the ability to acidify the YMA. Among the 27 isolates evaluated, 25 were able to grow when incubated at 42° C and 11 showed tolerance to 3% (w/v) of NaCl in YMA medium. The patterns of carbon sources utilization was very diverse among the isolates. It was observed the capacity of three strains to metabolize all the carbon sources evaluated and a total of 42% of the bacterial isolates was able to grow in the culture medium supplemented with at least, six carbon sources. The carbon sources mannitol (control) and sucrose were metabilized by all isolates evaluated. The profile of intrinsic resistance to antibiotics showed that the isolates were mostly resistant to streptomycin and ampicillin, but susceptible to kanamycin and chloranphenicol. High amylolytic activity of, at least, four isolates was also demonstrated, especially for isolated 47.3b, which showed the highest enzymatic index. These results indicate the metabolic versatility of the pigeonpea rhizobia, and indicates the isolate 47.3b to further studies regarding the amylase production and characterization.

As espécies de mucuna são muito utilizadas como adubos verdes, e poucas informações estão disponíveis a respeito dos rizóbios nativos capazes de nodulá-las. O objetivo deste trabalho foi avaliar a diversidade e a capacidade simbiótica de isolados bacterianos de nódulos de mucuna-cinza (Mucuna pruriens (L.) DC.) e mucuna-anã (Mucuna deeringiana (Bort.) Merr.). As bactérias foram isoladas de nódulos de mucunas cinza e anã cultivadas em vasos com solos de um sistema de produção agroecológica. Foram isoladas 160 bactérias, sendo 80 de mucuna-anã e 80 de mucuna-cinza, que foram autenticadas e selecionadas para avaliação da capacidade simbiótica. A diversidade dos isolados foi avaliada por meio das características culturais em meio de cultura YMA e da técnica de análise de restrição do produto de PCR do gene 16S rDNA. A inoculação de cinco isolados em mucuna-cinza e dois em mucuna-anã apresentou elevada biomassa da parte aérea. A maioria dos isolados apresentou crescimento rápido e acidificou o meio de cultura. A análise de restrição demonstrou que as bactérias isoladas apresentam baixa similaridade com estirpes de referência, sugerindo a existência de isolados pertencentes a novos grupos, capazes de nodular as mucunas anã e cinza.

The present work evaluated the germinability and vigor of Croton urucurana seeds. 1) Seeds were sorted by color (caramel, gray and black) and were subjected to seven different pre-germination treatments followed by incubation at 20ºC, 25°C or 20/30°C. 2) Seeds were stored in cold chambers or at room temperature for up to 300 days and were subsequently incubated at 20/30ºC in a germination chamber or under greenhouse conditions. Only gray seeds showed significant germination rates. The highest first count percentages of total germination and the highest germination speed indices were observed in control seeds and in those which were treated with water or 200 mg.L -1 gibberellic acid for 12 hours. Seeds stored under refrigeration showed the highest values for all of the characteristics examined, as well as less electrical conductivity of the imbibing solution. Seedlings were more vigorous when seeds were stored for 300 days in a cold chamber. The seedlings production can be increased by incubating the seeds at alternating temperatures (20/30°C). The seeds do not need pre-germination treatments.

Por meio deste estudo, objetivou-se estimar a rentabilidade de cultivares de soja em sistema de semeadura convencional (SSC) e direta (SSD) nos municípios de Campos dos Goytacazes e Quissamã, na região Norte Fluminense do Estado do Rio de Janeiro, utilizando-se o Valor Presente Líquido (VPL) e a Taxa Interna de Retorno (TIR). Buscouse identificar, por meio da análise de sensibilidade, os itens de maior peso na determinação da rentabilidade, além de estimar o risco de cada cultivar nos sistemas, via método de Monte Carlo. Em Campos dos Goytacazes, todas as cultivares avaliadas apresentaram rentabilidade satisfatória, sendo que os maiores VPL e TIR foram obtidos pela cultivar Vencedora em SSD. O preço da soja foi identificado como a variável de maior efeito sobre a rentabilidade para os dois sistemas, seguido das operações mecanizadas no SSC e fertilizantes no SSD. Nas condições da pesquisa, a cultivar mais promissora foi a Vencedora, quando cultivada no SSD, em Campos dos Goytacazes, oferece baixo risco econômico. Palavras-chave: rotação de culturas, Glycine max, Saccharum sp. ABSTRACT. Economic and risk evaluation of the soybean production in rotation with sugarcane in the North Fluminense Region. The objective of the study was to calculate the soy cultivar yield in systems of conventional sowing (SCS) and direct sowing (SDS) in Campos dos Goytacazes and Quissamã cities, in North Fluminense Region in the state of Rio de Janeiro, through Net Present Value (NPV) and the Internal Return Rate (IRR), identifying, by means of the sensitivity analysis, the most significant items to determine yield, besides estimating the risk of each cultivar in the systems through the Monte Carlo method. In Campos dos Goytacazes, all the cultivars presented acceptable yield. The largest ones are NPV and IRR, which were acquired by the 'Vencedora' in SDS cultivar. The price of the product was identified as the variable of strongest effect on the yield for the two systems, followed by the mechanized operations in SCS and fertilizers in SDS. Under research conditions, the most promising cultivar was 'Vencedora'. Once cultivated in the SDS in Campos dos Goytacazes, it offered low economic risk.