Industrial wastewater as raw material for exopolysaccharide production by Rhizobium leguminosarum

The objective of this study was to evaluate the exopolysaccharide (EPS) production by Rhizobium leguminosarum cultivated in wastewater generated by oil companies (WWOC1 and WWOC2) and fish processing industry (WWFP). The results obtained in Erlenmeyer flasks indicated that the rhizobial strain grew well in industrial wastewater. Generally, wastewater composition affected the growth and the EPS production. WWFP allowed good bacterial growth similar to that obtained with the standard medium (YMB). During growth, various quantities of EPS were produced and yields varied depending on the media. Growing in YMB, EPS production did not exceed 9.7 g/L obtained after 72 h of growth. In wastewater, the maximum EPS value reached 11.1 g/L obtained with the fish processing wastewater, after 72 h of growth. The use of a mixture of the oil company wastewater (WWOC2) and the fish processing wastewater (WWFP) as culture medium affected not only the rhizobial strain growth, but also EPS production. The highest EPS (42.4 g/L, after 96 h of culture) was obtained using a ratio of WWFP and WWOC2 of 50:50 (v:v). Therefore, this work shows the ability of Rhizobium leguminosarum, growing in industrial wastewater as new economic medium, to produce EPS. This biopolymer could be applied in enormous biotechnological areas.

Multilocus sequence analysis (MLSA) of Bradyrhizobium strains: revealing high diversity of tropical diazotrophic symbiotic bacteria

Symbiotic association of several genera of bacteria collectively called as rhizobia and plants belonging to the family Leguminosae (=Fabaceae) results in the process of biological nitrogen fixation, playing a key role in global N cycling, and also bringing relevant contributions to the agriculture. Bradyrhizobium is considered as the ancestral of all nitrogen-fixing rhizobial species, probably originated in the tropics. The genus encompasses a variety of diverse bacteria, but the diversity captured in the analysis of the 16S rRNA is often low. In this study, we analyzed twelve Bradyrhizobium strains selected from previous studies performed by our group for showing high genetic diversity in relation to the described species. In addition to the 16S rRNA, five housekeeping genes (recA, atpD, glnII, gyrB and rpoB) were analyzed in the MLSA (multilocus sequence analysis) approach. Analysis of each gene and of the concatenated housekeeping genes captured a considerably higher level of genetic diversity, with indication of putative new species. The results highlight the high genetic variability associated with Bradyrhizobium microsymbionts of a variety of legumes. In addition, the MLSA approach has proved to represent a rapid and reliable method to be employed in phylogenetic and taxonomic studies, speeding the identification of the still poorly known diversity of nitrogen-fixing rhizobia in the tropics.

Efectividad de cepas rizobianas de frijolbajo diferentes regímenes de fósforo / Effectiveness of cowpea rhizobial strains under different phosphorus regimes

En Venezuela, el frijol representa una alternativa a la proteína animal, debido a su alto consumo y valor nutritivo, por ello se ha estimulado la implementación de programas para reactivar la economía de los pequeños y medianos productores, a fin de incrementar su producción y así tener mayor disponibilidad de proteína de alta calidad a bajo costo; de manera que, los estudios encaminados a mejorar su cultivo, son acertados. Se evaluó la efectividad de cepas rizobianas de crecimiento lento (cl) y rápido (cr) en frijol (Vigna unguiculata (L.) Walp.) cultivar TC9-6 en varios regímenes de fósforo (0, 20, 40 y 80 kgP2O5 ha-1), con un diseño experimental de bloques al azar con arreglo factorial. Las plantas se cultivaron en 4 kg de suelo de sabana 45 días y las cepas en caldo de levadura y manitol: 5 (cr: JV91) y 10 (cl: JV94) días. La inoculación (2 ml cada vez) fue aplicada a la siembra y 6 días más tarde. La utilización de fósforo (40-80 kgP2O5 ha-1) incrementó la nodulación (número, peso seco total e individual de nódulos) y favoreció la aparición de nódulos rojos; así mismo, acrecentó el peso de la materia seca, la altura, el número de hojas y la concentración de nitrógeno del vástago. Los valores fueron similares con ambos tipos de cepas (efectividad similar) y para las dos concentraciones (40-80 kgP2O5 ha-1), con las menores estimaciones para 0 y 20 kgP2O5 ha-1. De acuerdo con los resultados las concentraciones de 40 y 80 kgP2O5 ha-1 fueron las más favorables para el crecimiento y la nodulación de frijol.

In Venezuela, cowpea is an alternative to animal protein due to its high consumption and nutritious value, so it has stimulated the implementation of programs to reactivate the small and medium producers economy, in order to increase its production and to have major high quality protein availability at low cost; so that, the studies carry on to improve its cultivation, are well-aimed. The effectiveness of slow (sg) and fast (fg) growing rhizobial strains was evaluated in cowpea (Vigna unguiculata (L.) Walp) cultivar TC9-6 at various phosphorus regimes (0, 20, 40 and 80 kgP2O5 ha-1): randomized block design with factorial arrangement. Plants were cultivated in 4 kg savannah soil: 45 days, and the strains in yeast and mannitol broth: 5 (fg: JV91) and 10 (sg: JV94) days. The inoculation (2 ml each time) was applied at sowing time and 6 days later. Phosphorus utilization (40-80 kgP2O5 ha-1) increased nodulation (nodule number, total and individual dry weight) and favoured nodule red colour appearance; also, incremented shoot dry matter weight, height, leaves number and nitrogen concentration. Values were similar with both strain types (similar effectiveness) and to the two doses (40-80 kgP2O5 ha-1), with lower estimations to 0 and 20 kgP2O5 ha-1. Accordingly with the results, the doses of 40 and 80 kgP2O5 ha-1 were the most favourable to cowpea growth and nodulation.

Bioassay for selection of biocontroller bacteria against bean common blight (Xanthomonas axonopodis pv. phaseoli)

Emphasis has been given on selection of micro-organism for biological control. However, in order to evaluate the biological control potential of a great number of micro-organisms in a small period of time it is necessary to develop an efficient bioassay. Seven hundred and sixty bacterial isolates from different habitats, were selected for compatibility with Rhizobium leguminosarum bv. phaseoli (SEMIA 4077 e SEMIA 4080). Among them 596 isolates were ineffective against both rhizobia. Bean seeds immersed in suspension of each one of these isolates were agitated for 5 hours at 10°C and sowed in non-sterilized soil. The plants were kept in greenhouse. After the development of cotyledonary and primary leaves, these were removed and bioassayed for Xanthomonas axonopodis pv. phaseoli (XAP) control. In the cotyledonary leaves, it was observed that the isolate DFs093 offered 100 percent control, DFs041 and DFs1297 offered 90 percent and DFs490, DFs769, DFs831, DFs842 and DFs843 offered 80 percent control. In the primary leaves, the DFs482 isolated offered 100 percent and the DFs080, DFs348, DFs513, DFs622, DFs769, DFs842 and DFs912 offered 80 percent of XAP control.

Tem-se dado muita ênfase ao controle biológico mediante seleção de microorganismos. Porém, para se avaliar o potencial de biocontroladores de forma massal e em pequeno intervalo de tempo é necessário desenvolver um bioensaio eficiente. Bactérias de diferentes sítios, num total de 760 isolados, foram selecionadas para compatibilidade com Rhizobium leguminosarum bv. phaseoli estirpes SEMIA 4077 e SEMIA 4080, onde 596 isolados foram inefetivos contra ambos rizóbios. Sementes de feijão foram imersas em suspensão de cada um destes isolados sendo agitadas por 5 horas a 10°C, plantadas em solo não esterelizado, sendo as plantas mantidas em casa de vegetação. Após o desenvolvimento das folhas cotiledonares e folhas primárias, estas foram retiradas e avaliadas por bioensaio para o controle de Xanthomonas axonopodis pv. phaseoli (XAP). Nas folhas cotiledonares, observou-se que o isolado DFs093, proporcionou 100 por cento de controle, DFs041 e DFs1297 propiciaram, 90 por cento e DFs490, DFs769, DFs831, DFs842 e DFs843 proporcionaram 80 por cento de controle. Nas folhas primárias, o isolado, DFs482 propiciou 100 por cento e os isolados DFs080, DFs348, DFs513, DFs622, DFs769, DFs842 e DFs912 proporcionaram 80 por cento de controle para XAP.

Assessment of cowpea rhizobium diversity in Cerrado areas of northeastern Brazil

Com o objetivo de contribuir com a otimização do processo de fixação biológica de nitrogênio (FBN) na cultura do caupi (Vigna unguiculata (L) Walp) no Cerrado do nordeste brasileiro, a diversidade de isolados de rizóbio obtidos em oito áreas de Cerrado com rotação de cultura bianual com soja, arroz e caupi. Foram realizadas caracterizações morfológicas (produção de muco e morfologia das colônias), genotípicas baseadas em ARDRA do 16S rDNA e resistência a antibióticos. Os resultados da caracterização morfológica mostraram uma correlação inversamente proporcional (p < 0,05) do índice de diversidade de Shannon-Waver com o número de cultivos de leguminosas (caupi e soja). Os dados de ARDRA mostraram que no Cerrado nativo somente foram observados isolados de Bradyrhizobium elkanii, corroborando com dados da literatura. Nas áreas onde haviam sido cultivadas leguminosas ocorreram dois fatos distintos; onde somente cultivou-se soja houve maior proporção de B. japonicum e onde cultivou-se soja e caupi, ocorreu maior proporção de B. elkanii. A análise de resistência a antibióticos mostrou cinco diferentes perfis de resistência. Maior resistência de Bradyrhizobium spp. foi encontrada em áreas cultivadas há mais tempo, e menor na área nativa e/ou áreas com poucos cultivos. De forma geral, pode-se observar uma relação inversa entre a diversidade de rizóbios e a resistência a antibióticos. Como a menor diversidade foi observada em áreas com maior número de cultivos de leguminosas, sugere-se que a presença da leguminosa pode favorecer condições ecológicas específicas, nas quais determinados grupos de rizóbios adquirem características competitivas importantes para seu estabelecimento.

Variability of isolated colonies in bean nodulating Rhizobium strains before and after exposure to high temperature

Irregular response to bean plants to Rhizobium inoculation has been attributed to among other factors, low competitive ability, low N2 fixation efficiency and genetic instability of the symbiont. This genetic instability caused by high rates of genomic rearrangements and/or plasmid deletions can be accentuated by high temperatures. This fact may limit the utilization of these strains as inoculants, especially in tropical soils. In this study, the variability of isolated colonies derived from effective R. leguminosarum bv. phaseoli (SLP1.3 and BR 10.026) and R tropici (SLA2.2 and BR322) strains was evaluated before and after exposure to high temperatures (four consecutive thermal shocks at 45ºC). This evaluation involved plant dry matter analysis of inoculated plants and genotypic (plasmid profile and genomic patterns via RAPD) analysis of the Rhizobium strains. The results evidenced that high temperature improve the natural performance variability especially between isolated colonies from R. leguminosarum bv. phaseoli strains. The plasmid profile of isolated colonies from R. tropici strains were identical regardless of temperature treatment whereas isolated colonies from R. leguminosarum bv. phaseoli alterations were detected especially after the thermal treatment. The genomic patterns generated by AP-PCR showed more alterations and genetic variation in isolated colonies from R. leguminosarum bv. phaseoli strains indicating that R. tropici strains are more stable and lower affected by high temperature.

Host plant nodule parameters associated with nitrogen fixation efficiency in French bean (Phaseolus vulgaris L) cultivars.

Two cultivars of French bean (Phaseolus vulgaris L.) viz. contender and arka komal were planted in polythene bags containing sand and grown under glasshouse conditions. The nodulation status, shoot/root biomass, activities of several nodule enzymes, total soluble protein and leghaemoglobin contents were monitored over the entire growth period. Allantoinase activity in leaves was measured to monitor the ureide degrading capacity. Significant genotype difference was observed in both the cultivars. All the parameters showed a decline after flowering except uricase, which declined before flowering. Malate dehydrogenase and isocitrate dehydrogenase showed a constant decline throughout the growth period. Degree of decline varied with the genotype for all the parameters. Leghaemoglobin content, PEP carboxylase activity and ureide degrading capacity of leaves did not show an appreciable decline in contender and were significantly higher than in arka komal. These factors can be used to increase nitrogen fixation in French bean.

Genetics of thermotolerance in ciprofloxacin resistant mutant of Rhizobium leguminosarum bv phaseoli.

A ciprofloxacin resistant mutant (Cf(R)) of Rhizobium leguminossarum bv phaseoli USDA 2695 which nodulates common bean plants (Phaseolus vulgaris L) was isolated after nitrous acid mutagenesis. Another mutant resistant to nalidixic acid (Nal(R)) was isolated spontaneously. Both mutants showed thermotolerance as evident by their ability to grow at elevated (40 degrees C) temperature, although the wild type (USDA 2695) failed to grow at this temperature. Transformation and plasmid curing experiments suggested the gene(s) controlling thermotolerance (TrR) and resistance to nalidixic acid or ciprofloxacin were located on the main chromosome and not on the plasmids. High frequency of co-transfer of TrR-Cr(R) and Tr(R)-Nal(R) during transformation experiments indicated a close association of these gene(s). Role of DNA gyrase and supercoiling in these thermotolerant mutants has been discussed.

Random amplified polymorphic DNA analysis of effective "Rhizobium" sp. associated with beans cultivated in brazilian cerrado soils

Efficient bean nodulating Rhizobium strains, isolated from different Brazilian cerrado soils, were characterized by RAPD. This study showed great genetic heterogeneity among R. tropici and R. leguminosarum bv. phaseoli strains and allowed the constitution of genetic clusters, besides indicating the most suitable primers for this characterization. The groups of genetically distinct strains can be used in competitiveness studies to select appropriate Rhizobium strains for bean inoculation in cerrado soils.

Efecto de la adición de lectina específica sobre la simbiosis Rhizobium leguminosarum--Phaseolus vulgaris / Effect of the addition of specific lectin on the symbiosis of Rhizobium leguminosarum and Phaseolus vulgaris

The effect of specific lectin addition on Rhizobium leguminosarum-Phaseolus vulgaris symbiosis characteristics was studied. Two alternatives were selected for comparison: a) P. vulgaris seedling roots treated with lectin were inoculated with R. leguminosarum and b) P. vulgaris seedling roots were inoculated with R. leguminosarum incubated with lectin for 3 h and 72 h. The following parameters were evaluated: number and dry weight of nodules and dry matter and nitrogen content of shoot. In lectin treatments, the weight of nodules (from 13 to 35), dry matter (from 6 to 18) and nitrogen content (from 5 to 28) increased significantly. The results suggest a stimulation in the formation of functional-nodules, specially in root (a) and Rhizobium (b) 72 h treatments. That is consistent with a model in which the lectin functions as an extracellular matrix component of the root interacting with roots and Rhizobium s.p. receptors.

Effectes of high temperature on survival, symbiotic performance and genomic modifications of bean nodulating Rhizobium strains

High temperatures can affect the survival, establishment and symbiotic properties of "Rhizobium" strains. Bean nodulating "Rhizobium" strains are considered particularly sensitive because on this strains genetic recombinations and/or deletions occur frequently, thus compromising the use of these bacteria as inoculants. In this study "R. tropici" and "R. leguminosarum" bv. "phaseoli" strains isolated from Cerrado soils were exposed to thermal stress and the strains' growth, survival and symbiotic relationships as well as alterations in their genotypic and phenotypic were analysed. After successive thermal shocks at 45ºC for four hours, survival capacity appeared to be strain-specifc, independent of thermo-tolerance and was more apparent in "R. tropici" strains (with the exception of FJ2.21) were more stable than "R. leguminosarum" bv. "phaseoli" strains because no significant phenotypic alterations were observed following thermal treatments and they maintained their original genotypic pattern after innoculation in plants.

Partial characterization of bacteriophages active against rhizobium leguminosarum Isolated from some Egyptian soils

Seventeen rhizobiophages infective against Rhizobium leguminosarwn were isolated from field grown Vicia faba in AI-Ibrahimia [Sharkia Governorate-Egypt]. Morphology, host range and inactivation pattern of the phage to heat and UV-light were studied. Isolated phages had isometric heads and tails which were contractile [2 phages], long and non contractile [7 phages], or very short tails [8 phages]. The phages were members of Bradley's basic morphological groups A, B and C. Most of these phages showed, specificity for their host [R. leguminosarune local strain] and distinct rates of sensitivity against heat and UV

Estudo da influência de agrotóxicos sobre o desenvolvimento do Rhizobium leguminosarum biovar phaseoli / Study of the agrotoxics influence over the development of the Rhizobium leguminosarum biovar phaseoli

As bactérias fixadoras de nitrogênio atmosférico, via processo simbiótico, repassam N2 às leguminosas sob forma de amônia, proporcionando aumento na produçäo de alimentos protéicos, reciclagem biológica de nitrogênio do ar, evitando o alto custo da adubaçäo nitrogenada e o efeito potencialmente poluidor do nitrato lixiviado. Testou-se quatro estirpes de Rhizobium phaseoli frente a quatro fungicidas indicados para o tratamento de sementes de Phaseolus vulgaris L. (feijoeiro), no Estado do Rio Grande o sul (Brasil). Considerando-se as dosagens recomendadas dos fungicidas, houve crescimento bacteriano das quatro estirpes frente a Benomil e inibiçäo total frente a Captan; porém, para PCNB e Thiram, a resistência dependeu do tipo de estirpe. Observou-se que näo há influência de fungicidas sobre o desenvolvimento do Rhizobium phaseoli quando seleciona-se a estirpe adequada ao fungicida corretamente dosado.

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

Composiçäo química e valor nutricional de cultivares de gräo-de-bico produzidos no Estado de Säo Paulo / Chemical composition and nutritional value of chickpea cultivars grown in the State of Säo Paulo

Foram analisados a composiçäo química e valor nutricional de cultivares de gräo-de-bico produzidos no Estado de Säo Paulo. Estudou-se também seu aproveitamento na forma de farinha. O cultivar IAC-México apresentou maior teor de proteína (19,7 por cento). O teor de fibra alimentar total foi maior para as sementes marrom e preta. Todos os cultivares apresentaram menor atividade de inibidor de tripsina que a soja e as sementes escuras apresentaram teores maiores de compostos fenólicos do que as sementes claras. A composiçäo em minerais demonstra que este gräo é uma boa fonte de fósforo, magnésio, ferro, potássio e manganês. Embora deficientes em aminoácidos sulfurados, os cultivares apresentaram um quociente de eficiência protéica líquida (NPR) e quociente de eficiência protéica (PER) superiores a 80 por cento do valor obtido para a caseína e digestibilidade em torno dos 80 por cento

Composiçäo química, processamento e avaliaçäo do broto-de-bambu D. giganteus Munro processado / Chemical composition, processing and evaluation of bamboo shoots D. giganteus Munro

O broto-de-bambu Dendrocalamus giganteus Munro, dividido nas porçöes apical e basal, foi estudado quanto aos aspectos de composiçäo química, processamento e características físicas e organolépticas de aceitabilidade do produto processado. As etapas envolvidas no processamento foram discutidas detalhadamente. O broto-de-bambu se caracteriza como vegetal de baixa acidez e apresenta níveis de HCN no produto processado foram da ordem de 742 mg/kg e 532 mg/kg nas porçöes apical e basal, respectivamente. Os níveis máximos residuais de HCN no produto processado foram da ordem de 76,0 e 59,4 mg/kg para as porçöes apical e basal. O rendimento obtido de broto-de-bambu processado foi de 35,9 por cento em relaçäo à matéria-prima. As duas porçöes do broto-de-bambu foram classificadas entre o "gostei" e "gostei muito" da escala hedônica facial empregada no teste de aceitaçäo

Curvas de equilíbrio higroscópico de três genótipos de gräo-de-bico (Cicer arietinum, L) / Sorption equilibrium moisture contents of three genotypes of chickpea (Cicer arietinum, L.)

A equaçäo de BET foi utilizada no ajuste de curvas de equilíbrio higroscópico de adsorçäo de dessorçäo de 3 genótipos de gräo-de-bico (Cicer arietinum, L): o cultivar IAC-Marrocos e as linhagens Sonora e IAC-Sonora-FE. As umidades de equilíbrio foram obtidas em condiçöes ambientais controladas, pelo método estático, com umidade relativa de equilíbrio variando de 10 a 90 por cento com intervalo de 10 por cento (utilizando-se soluçäo de ácido sulfúrico) e temperatura de 25 + ou - 2 graus centígrados. O ajuste das curvas e a obtençäo das constantes da equaçäo de BET foram realizados por meio de regressäo näo linear, utilizando-se o procedimento PROC.NLIN do SAS, para os dados experimentais de equilíbrio nas condiçöes de 10 a 80 por cento de UR. Os dados experimentais correspondentes à umidade relativa de 90 por cento näo foram considerados, pois as amostras apresentaram alteraçöes visuais de causa desconhecida. A equaçäo de BET mostrou-se adequada para o ajuste das isotermas de sorçäo dos 3 genótipos de gräos-de-bico, sendo que, para todas as curvas, o melhor ajuste foi obtido para seis camadas polimoleculares (n=6). De acordo com os parâmetros de BET estimados para n=6, os menores valores de teor de umidade da monocamada molecular correspondem às curvas de dessorçäo, ao passo que as menores energias de sorçäo corresponderam às curvas de adsorçäo, para os 3 genótipos analisados

Prevalence in Egyptian soils of r leguminosarum biovar viceae and their physiological properties

A survey was carried out on the prevalence of indigenous Rhizobium leguminosarum in different Nile Delta soils of Egypt. In addition, 163 strains of this bacterium were isolated from nodules of faba bt-an [Vicia faba] plants grown in the 40 locations under investigation to study some physiological characteristics of the indigenous bacteria as well as to determine their capacity in N[2]-fixation. Results showed that R.leguminosarum is present in soil in relatively low numbers [ca. 10[3] cells g[-1]] being the highest in the heavy teatured soils. Faba bean plants collected from Ismailia governor ate generally beared the highest number of nodules on their root systems [average of 43 plant[-1]] while those taken from Qalubia produced the lowest number [9 plant[-1]]. Out of the 163 R.leguminosarum isolated, 98 [ca. 60%] were sensitive towards all tested antibiotics [neomycin, kanamycin and streptomycin] at the given concentrations, only 19 isolates [11.7%] could resist the presence of the three compounds even applied at the highest concentrations, in comparison with the control medium containing 0.01% NaCl, 89 isolates [55%] could not grow at a salt level of 1% or more, mean while only 3 isolates [2%] did survive at 6% NaCl. No visible growth was observed in 8% salted medium. 59 isolates [36.2%] failed to withstand temperature as high as 35° or more, while 62 strains did grow fairly up to 35°. Only 8 strains could resist 45° for die 7 days of incubation. The 163 isolates widely differed in their ability to jwovide faba bean plants with fixed nitrogen. They could be classified into five categories namly; ineffective, slightly, moderately, highly and very highly effective [5. 46, 51, 45 and 16 isolates respectively]

Response of chickling vetch [lathyrus sativus L] and forage peas [pisum spp] to inoculation with rhizobium leguminosarum in north Sinai coastal soils

Field experiments were conducted in sandy soil at Rafah, north sinai, to study the performance of two Rhizobium leguminosarum strains [TAL 634 and F9] with vetch, grasspea [Lathyrus sativus] and forag peas [Pisum spp.]. Inoculation of both crops with these strains, either singly or in combination, induced significant increases in plant dry weight, N2 fixation and seed yield. No significant differences, in plant N content or seed yield, were obtained between the two rhizobial strains and/or their mixtures for both crops. The competitive ability of inoculant strains differed with the host plant. Strain TAL 634 was more competitive than strain F9 with chickling vetch. In double strain inocula, strain TAL 634 occupied 40% of nodules versus 15% for F9. With forage peas, strain F9 was more competitive than strain TAL 634. The strain F9 occupied 45% of nodules versus 30%for strainTAL634