Review: A brief story of nitrogen fixation in sugarcane - reasons for success in Brazil.

Sugarcane was first introduced into Brazil in 1532, in São Vicente (São Paulo State) by the Portuguese. Since the first cane selection and breeding programs started in Brazil, both local and introduced material were used. In none of the breeding programs were large amounts of nitrogen fertilizer utilized, and this may be the reason why today the best materials have little demand for nitrogen fertilizer, and an effective association has developed between endophytic nitrogen-fixing bacteria and the plant. In some cases high inputs of associated biological nitrogen fixation have been observed. The oil crisis also played a role in the sugarcane story, since the alcohol-from-cane-juice (PRO-ÁLCOOL) program installed to find a substitute for gasoline in cars, stimulated the selection of highly efficient varieties with low nitrogen fertilizer input. The recent promising results involving the inoculation of micropropagated sugarcane plants with endophytic diazotrophic bacteria, along with the ongoing Brazilian sugarcane plant and bacterial genome programs, suggest that the success of the Brazilian sugarcane business may continue for many years to come, considering the potential to be exploited.

Herbaspirillum-like bacteria in banana plants

Diazotrophic bacteria isolated from banana plants were characterized by morphological and physiological aspects. Three different groups of these plant-bacteria could be established. Two of them showed similarity to species of the Herbaspirillum genus. The third one was different because used only a few carbon substrates and produced water diffusible compounds that fluoresced under UV light. All three bacterial groups were thin rods with mono or bipolar flagella, presented negative reaction in Gram stain, showed catalase activity, were able to reduce nitrate and grew better in semi-solid JNFb medium at 31§C. The nitrogenase activity was detected in semi-solid N-free JNFb medium and expressed higher values when pH ranged from 6.5 to 7.0 (groups I and II) and 6.0 to 6.5 (group III). The diazotrophs isolated from banana plants were distinct from species of Herbaspirillum previously identified in gramineous plants.

Seleçäo e caracterizaçäo de estirpes de rhizobium estáveis e capazes de fixar nitrogênio em feijäo(phaseolus vulgaris L.) / Selection and characterization of rhizobium spp.strains stable and capable in fixing nitrogen in bean(phaseolus vulgaris L.)

resumo:Determinou-se a variabilidade na capacidade de fixaçäo de N2, através de testes de reduçäo de acetileno em nódulos formados por estirpes de Rhizobium, antes e após exposiçäo das bactérias "in vitro" à temperaturas elevadas (38-39ºC).Nódulos formados tanto por estirpes de R.leguminosarum bv.phaseoli como R.tropici mais tolerantes a altas temperaturas quando inoculadas em feijäo, näo sofreram alteraçöes nas características simbióticas tais como, atividade de nitrogenase, peso seco de planta e nitrogênio total fixado.O padräo de proteínas(eletroforese SDS-PAGE) diferenciou estirpes entre e dentro das espécies.A hibridizaçäo do DNA total usando "nifprob" marcada via "nick translation"(biotina 14 dATP), quando a digestäo foi efetuada com EcoRI, diferenciou a espécie de R.leguminosarumbv.phaseoli de R.tropici.Foi observado polimorfismo entre as estirpes de R.leguminosarum bv.phaseoli após digestäo com Bam HI e entre R.leguminosarum bv.phaseoli e R.tropici após a digestäo com Hind III.Näo foram detectadas alteraçöes nos padröes protéicos ou genômicos e na atividade da nitrogenase da mesma estirpe antes e após crescimento a temperaturas elevadas, indicando que as estirpes de ambas as espécies(R.leguminosarum bv.phaseoli e R.tropici), tolerantes a altas temperaturas säo também mais estáveis geneticamente

Ocorrência de nodulação em leguminosas florestais de terra firme nativas da região de Manaus-AM

Summary A survey on seedling nodulation of native leguminous forest species was made in an area near Manaus, Amazonas, Brazil, with typical humid tropical forest vegetation on yellow oxisols of varying textures. This survey was made by collecting seedling from the forest with intact root systems, registering the presence of nodules and the type of soil were the collection was made. Seedlings were transplanted to polyethylene bags with a horizon forest soil to verify if nodulation by native Rhizobium sp. occurs in nursery conditions. One year later observations were made for: presence of nodules, nitrogenase activity, as well as some nodule characteristics. Of the 34 species, 22 showed nodulation. Of these nine belonged to the subfamily Mimosoideae, six to Caesalpinioideae and four to Papilionoideae. Of these twelve were collected on sandy soils and six on clay soil and one in the two types of soil. Capacity of nodulation was observed in some species that were not reported in a recent revision as being able to nodulate before (Cedrelinga catenaeformis, Diplotropis purpurea and Tachigalia sp).

Resumo Fez-se um levantamento da nodulação em mudas de espécies florestais nativas, em área próxima de Manaus na Amazônia, caracterizada por uma vegetação do tipo tropical úmida de terra firme, em Latossolo Amarelo de várias texturas. Este levantamento foi feito com a extração de mudas com sistema radicular intacto, sendo registrada a presença de nódulos e o tipo de solo em que se fez a coleta. Estas mudas foram transplantadas para recipientes plásticos com solo de floresta, com o objetivo de verificar se ocorria nodulação por Rhizobium nativo em condições de viveiro. Após um ano, sob estas condições, foram feitas observações da presença de nódulos, atividade da nitrogenase, bem como algumas características dos nódulos. Das 34 espécies pesquisadas, 22 mostraram-se capazes de nodular. Destas, nove são da subfamília Mimosoideae, seis da Caesalpinioideae e quatro da Papilionoideae, sendo que doze foram coletadas em solo arenoso, seis em solo argiloso e uma nos dois tipos de solo. Baixas atividades da nitrogenase foram encontradas na maioria das espécies. Foi observada a ocorrência de nódulos em algumas espécies (Cedrelinga catenaeformis, Diplotropis purpurea e Tachigalia sp.) que não haviam sido mencionadas como capazes de nodular em recente revisão.