Abstract Drought limits wheat production in the Brazilian Cerrado biome. In order to search for candidate genes associated to the response to water deficit, we analyzed the gene expression profiles, under severe drought stress, in roots and leaves of the cultivar MGS1 Aliança, a well-adapted cultivar to the Cerrado. A set of 4,422 candidate genes was found in roots and leaves. The number of down-regulated transcripts in roots was higher than the up-regulated transcripts, while the opposite occurred in leaves. The number of common transcripts between the two tissues was 1,249, while 2,124 were specific to roots and 1,049 specific to leaves. Quantitative RT-PCR analysis revealed a 0.78 correlation with the expression data. The candidate genes were distributed across all chromosomes and component genomes, but a greater number was mapped on the B genome, particularly on chromosomes 3B, 5B and 2B. When considering both tissues, 116 different pathways were induced. One common pathway, among the top three activated pathways in both tissues, was starch and sucrose metabolism. These results pave the way for future marker development and selection of important genes and are useful for understanding the metabolic pathways involved in wheat drought response.

Resumo O objetivo deste trabalho foi analisar a resposta androgênica de genótipos brasileiros de trigo a diferentes pré-tratamentos das espigas, antes da cultura de micrósporos isolados, e ao efeito de um agente gelificante no meio de cultura de indução. Cinco genótipos foram avaliados quanto à formação de embriões, regeneração de plantas verdes e à duplicação espontânea dos cromossomos. Espigas de trigo foram submetidas a dois pré-tratamentos: frio, a 4ºC por 21 dias; e ácido 2-hidroxinicotínico, a 32ºC por dois dias. Os meios de cultura foram avaliados com ou sem Ficoll como agente gelificante. O frio produziu mais embriões e plantas verdes do que o pré-tratamento químico, em quatro dos cinco genótipos testados. Apenas dois genótipos tratados com ácido 2-hidroxinicotínico foram capazes de produzir plantas, e um deles produziu uma única planta albina. O meio com Ficoll produziu mais embriões do que o meio líquido e gerou maior número de plantas. A duplicação espontânea dos cromossomos varia entre os genótipos e os pré-tratamentos e apresenta alta variabilidade.

Abstract The objective of this work was to analyze the androgenic response of Brazilian wheat genotypes to different pretreatments of the spikes, prior to the culture of isolated microspores, and to the effect of a gelling agent in the induction culture medium. Five genotypes were evaluated for embryo formation, green plant regeneration, and spontaneous chromosome duplication. Wheat spikes were subjected to two pretreatments: cold, at 4ºC for 21 days; and 2-hydroxynicotinic acid, at 32ºC for two days. Culture media were evaluated with or without Ficoll as a gelling agent. Cold produced more embryos and green plants than the chemical pretreatment in four out of five genotypes. Only two genotypes treated with 2-hydroxynicotinic acid were able to produce plants, and one of them produced a single albino plant. Medium containing Ficoll produced more embryos than liquid medium and promoted a higher number of plants. Spontaneous chromosome duplication varies between genotypes and pretreatments, and shows high variability.

Soybean [Glycine max (L.) Merril], one of the most important crop species in the world, is very susceptible to abiotic and biotic stress. Soybean plants have developed a variety of molecular mechanisms that help them survive stressful conditions. Hybrid proline-rich proteins (HyPRPs) constitute a family of cell-wall proteins with a variable N-terminal domain and conserved C-terminal domain that is phylogenetically related to non-specific lipid transfer proteins. Members of the HyPRP family are involved in basic cellular processes and their expression and activity are modulated by environmental factors. In this study, microarray analysis and real time RT-qPCR were used to identify putative HyPRP genes in the soybean genome and to assess their expression in different plant tissues. Some of the genes were also analyzed by time-course real time RT-qPCR in response to infection by Phakopsora pachyrhizi, the causal agent of Asian soybean rust disease. Our findings indicate that the time of induction of a defense pathway is crucial in triggering the soybean resistance response to P. pachyrhizi. This is the first study to identify the soybean HyPRP group B family and to analyze disease-responsive GmHyPRP during infection by P. pachyrhizi.

Transgenic plants represent an invaluable tool for molecular, genetic, biochemical and physiological studies by gene overexpression or silencing, transposon-based mutagenesis, protein sub-cellular localization and/or promoter characterization as well as a breakthrough for breeding programs, allowing the production of novel and genetically diverse genotypes. However, the stable transformation of soybean cannot yet be considered to be routine because it depends on the ability to combine efficient transformation and regeneration techniques. Two methods have been used with relative success to produce completely and stably transformed plants: particle bombardment and the Agrobacterium tumefaciens system. In addition, transformation by Agrobacterium rhizogenes has been used as a powerful tool for functional studies. Most available information on gene function is based on heterologous expression systems. However, as the activity of many promoters or proteins frequently depends on specific interactions that only occur in homologous backgrounds, a final confirmation based on a homologous expression system is desirable. With respect to soybean biotech improvement, transgenic lines with agronomical, nutritional and pharmaceutical traits have been obtained, including herbicide-tolerant soybeans, which represented the principal biotech crop in 2011, occupying 47% of the global biotech area.

Environmental stresses caused by either abiotic or biotic factors greatly affect agriculture. As for soybean [Glycine max (L.) Merril], one of the most important crop species in the world, the situation is not different. In order to deal with these stresses, plants have evolved a variety of sophisticated molecular mechanisms, to which the transcriptional regulation of target-genes by transcription factors is crucial. Even though the involvement of several transcription factor families has been widely reported in stress response, there still is a lot to be uncovered, especially in soybean. Therefore, the objective of this study was to investigate the role of bHLH and trihelix-GT transcription factors in soybean responses to environmental stresses. Gene annotation, data mining for stress response, and phylogenetic analysis of members from both families are presented herein. At least 45 bHLH (from subgroup 25) and 63 trihelix-GT putative genes reside in the soybean genome. Among them, at least 14 bHLH and 11 trihelix-GT seem to be involved in responses to abiotic/biotic stresses. Phylogenetic analysis successfully clustered these with members from other plant species. Nevertheless, bHLH and trihelix-GT genes encompass almost three times more members in soybean than in Arabidopsis or rice, with many of these grouping into new clades with no apparent near orthologs in the other analyzed species. Our results represent an important step towards unraveling the functional roles of plant bHLH and trihelix-GT transcription factors in response to environmental cues.

O objetivo deste trabalho foi realizar a triagem de genótipos de soja quanto à sua habilidade de resposta à indução de raízes fasciculadas por transformação mediada por Agrobacterium rhizogenes. Quatro cultivares brasileiras de soja (BRSMG 68 Vencedora, BRS 137, Embrapa 48 e MG/BR 46 Conquista) e duas norte americanas, adaptadas às condições brasileiras de cultivo (Bragg e IAS‑5), foram avaliadas quanto à sua capacidade de responder a A. rhizogenes, em protocolos de cultura de raízes fasciculadas in vitro e de produção ex vitro de plantas compostas. Plântulas com quatro dias de idade, de tamanho uniforme, foram injetadas com A. rhizogenes portando o plasmídeo p35S‑GFP. As plântulas que expressaram a proteína verde fluorescente (GFP) em pelo menos uma raiz foram utilizadas para determinar a frequência de transformação. Utilizando um protocolo de obtenção de raízes axênicas, in vitro, cotilédones excisados de plântulas com quatro dias de idade foram infectados com A. rhizogenes portando o plasmídeo pCAMBIA1301 contendo o gene repórter gusA. Foram avaliados a frequência de transformação e o número de dias para emergência das raízes fasciculadas após a infecção bacteriana (DAI). A frequência de transformação e o DAI variaram conforme o genótipo. As cultivares MG/BR 46 Conquista e BRSMG 68 Vencedora são mais suscetíveis a A. rhizogenes e podem ser recomendadas para experimentos de transformação.

The objective of this work was to perform the screening of soybean genotypes as to their ability to respond to the induction of hairy roots by Agrobacterium rhizogenes‑mediated transformation. Four Brazilian soybean cultivars (BRSMG 68 Vencedora, BRS 137, Embrapa 48, and MG/BR 46 Conquista) and two North American ones adapted to Brazilian cropping conditions (Bragg and IAS‑5) were screened for their capacity to respond to A. rhizogenes in protocols for in vitro hairy root culture and ex vitro composite plant production. Four‑day‑old seedlings with uniform size were injected with A. rhizogenes harboring the plasmid p35S‑GFP. Seedlings expressing green fluorescent protein (GFP) in at least one hairy root were used to determine the transformation frequency. Using an axenic in vitro protocol, excised cotyledons from four‑day‑old seedlings were infected with A. rhizogenes harboring the pCAMBIA1301 plasmid, containing the gusA reporter gene. The transformation frequency and the number of days for hairy root emergence after bacterial infection (DAI) were evaluated. The transformation frequency and DAI varied according to the genotype. Cultivars MG/BR 46 Conquista and BRSMG 68 Vencedora are more susceptible to A. rhizogenes and can be recommended for transformation experiments.

O objetivo deste trabalho foi identificar cultivares brasileiras de soja (Glycine max) com capacidade de resposta aos estímulos da cultura in vitro para a indução de embriões somáticos primários, proliferação de embriões secundários e regeneração de plantas. Foram observadas diferenças para cada estádio entre as oito cultivares testadas. Foram selecionadas duas cultivares, 'IAS-5' e BRSMG 68 Vencedora, para avaliação do potencial dos embriões quanto à diferenciação e conversão em plantas. Essas cultivares tiveram altas taxas de indução, proliferação embriogênica repetitiva e baixa germinação precoce dos embriões, no experimento inicial. Foi investigado o efeito da adição de ácido abscísico (ABA) e carvão sobre a regeneração. Os resultados mostraram que a adição de ABA ao meio de proliferação e de ABA e carvão ativado ao meio de maturação aumentaram as taxas de diferenciação dos embriões, o que resultou em maior número de plantas regeneradas. A cultivar BRSMG 68 Vencedora foi identificada como genótipo com alto potencial para indução e proliferação de embriões, bem como para regeneração de plantas. O potencial dessa cultivar quanto à embriogênese somática foi similar ao observado para a cultivar IAS-5, atualmente utilizada para transformação de soja no Brasil. A BRSMG 68 Vencedora pode ser um genótipo alternativo para a engenharia genética de soja via protocolos de embriogênese somática.

The aim of this work was to identify Brazilian soybean (Glycine max) genotypes with potential to respond to in vitro culture stimuli for primary somatic embryo induction, secondary embryo proliferation and plant regeneration. Differences among eight tested cultivars were observed at each stage. Two cultivars, IAS-5 and BRSMG 68 Vencedora, were selected for the evaluation of the capacity for embryo differentiation and plant regeneration. These cultivars had high embryo induction frequencies, repetitive embryogenic proliferation, and low precocious embryo germination in the initial experiment. The effect of abscisic acid (ABA) and charcoal addition on plant regeneration was investigated. The addition of ABA to proliferation medium and of ABA and activated charcoal to maturation medium increased embryo differentiation rates, which resulted in a higher number of regenerated plants. The BRSMG 68 Vencedora cultivar was found to have a high potential for embryo induction, embryo proliferation and plant regeneration. The potential of this cultivar for somatic embryogenesis was similar to that observed for cultivar IAS-5, which is currently used for soybean transformation in Brazil. BRSMG 68 Vencedora may be a good alternative genotype for soybean genetic engineering via somatic embryogenesis protocols.

Duas linhagens bacterianas que apresentaram amplificação de parte do gene nifH, RP1p e RP2p, pertencentes aos gêneros Enterobacter e Serratia, foram isoladas do rizoplano de Lupinus albescens. Essas bactérias são Gram-negativas, com formato de bastonete, móveis, anaeróbias facultativas e apresentam multiplicação rápida, com colônias alcançando diâmetros de 3-4 mm em 24 h de incubação a 28 ºC. RP1p e RP2p também foram capazes de multiplicação em temperaturas elevadas, como 40 ºC, na presença de alta concentração de NaCl (2-3 % v/v) e em valores de pH que variaram de 4 a 10. A linhagem RP1p foi capaz de utilizar 10 das 14 fontes de carbono avaliadas, enquanto a linhagem RP2p utilizou nove. Os isolados produziram sideróforos e compostos indólicos, mas foram incapazes de solubilizar fosfatos. A inoculação de L. albescens com as linhagens RP1p e RP2p resultou em aumento significativo do peso das plantas secas, o que demonstra que essas bactérias apresentam propriedades que favorecem o crescimento vegetal.

Two bacterial strains that amplified part of the nifH gene, RP1p and RP2p, belonging to the genus Enterobacter and Serratia, were isolated from the rhizoplane of Lupinus albescens. These bacteria are Gram-negative, rod-shaped, motile, facultative anaerobic, and fast-growing; the colonies reach diameters of 3-4 mm within 24 h of incubation at 28 ºC. The bacteria were also able to grow at temperatures as high as 40 ºC, in the presence of high (2-3 % w/v) NaCl concentrations and pH 4 -10. Strain RP1p was able to utilize 10 of 14 C sources, while RP2p utilized nine. The isolates produced siderophores and indolic compounds, but none of them was able to solubilize phosphate. Inoculation of L. albescens with RP1p and RP2p strains resulted in a significant increase in plant dry matter, indicating the plant-growth-promoting abilities of these bacteria.

O objetivo deste trabalho foi analisar a performance agronômica e a estabilidade cromossômica de progênies transgênicas homozigotas de soja [Glycine max (L.) Merrill.], e confirmar a resistência dessas plantas a Anticarsia gemmatalis. Onze progênies com expressão dos genes cry1Ac, hpt e gusA foram avaliadas quanto às características agronômicas, em relação à cultivar parental IAS 5 não transformada. Análises citogenéticas foram realizadas em plantas transgênicas e não transgênicas. Duas das 11 progênies transgênicas também foram avaliadas quanto à resistência a A. gemmatalis, em bioensaios in vitro e in vivo. Dois controles negativos foram utilizados nos bioensaios: uma linha transgênica homozigota, com apenas o gene repórter gusA, e plantas de 'IAS 5' não transgênicas. A presença do transgene cry1Ac não afetou nem o desenvolvimento nem a produtividade das plantas. As plantas transgênicas apresentaram cariótipo normal. No bioensaio com folhas destacadas, as plantas cry1Ac exibiram completa eficácia contra A. gemmatalis, enquanto os controles negativos foram significativamente danificados. Ensaios com plantas inteiras confirmaram a elevada proteção do cry1Ac contra a lagarta-da-soja, enquanto as plantas 'IAS 5' não transgênicas e a linha homozigota gusA exibiram 56.5 e 71.5% de desfolhação, respectivamente. A presença do transgene cry1Ac não afeta a performance agronômica da soja (incluindo a produtividade) e confere elevada proteção a A. gemmatalis.

The objective of this work was to analyze the agronomic performance and chromosomal stability of transgenic homozygous progenies of soybean [Glycine max (L.) Merrill.], and to confirm the resistance of these plants against Anticarsia gemmatalis. Eleven progenies expressing cry1Ac, hpt and gusA genes were evaluated for agronomic characteristics in relation to the nontransformed parent IAS 5 cultivar. Cytogenetical analysis was carried out on transgenic and nontransgenic plants. Two out of the 11 transgenic progenies were also evaluated, in vitro and in vivo, for resistance to A. gemmatalis. Two negative controls were used in resistance bioassays: a transgenic homozygous line, containing only the gusA reporter gene, and nontransgenic 'IAS 5' plants. The presence of cry1Ac transgene affected neither the development nor the yield of plants. Cytogenetical analysis showed that transgenic plants presented normal karyotype. In detached-leaf bioassay, cry1Ac plants exhibited complete efficacy against A. gemmatalis, whereas negative controls were significantly damaged. Whole-plant feeding assay confirmed a very high protection of cry1Ac against velvetbean caterpillar, while nontransgenic 'IAS 5' plants and homozygous gusA line exhibited 56.5 and 71.5% defoliation, respectively. The presence of cry1Ac transgene doesn't affect the majority of agronomic traits (including yield) of soybean and grants high protection against A. gemmatalis.

Somatic embryos of the commercial soybean (Glycine max) cultivar IAS5 were co-transformed using particle bombardment with a synthetic form of the Bacillus thuringiensis delta-endotoxin crystal protein gene cry1Ac, the beta-glucuronidase reporter gene gusA and the hygromycin resistance gene hpt. Hygromycin-resistant tissues were proliferated individually to give rise to nine sets of clones corresponding to independent transformation events. The co-bombardment resulted in a co-transformation efficiency of 44%. Many histodifferentiated embryos and 30 well-developed plants were obtained. Twenty of these plants flowered and fourteen set seeds. The integration and expression of the cry1Ac, gusA and hpt transgenes into the genomes of a sample of transformed embryos and all T0, T1, T2 and T3 plants were confirmed by Gus activity, PCR, Southern and western blot, and ELISA techniques. Two T0 plants out of the seven co-transformed plants produced seeds and were analyzed for patterns of integration and inheritance until the T3 generation. Bioassays indicated that the transgenic plants were highly toxic to the velvetbean caterpillar Anticarsia gemmatalis, thus offering a potential for effective insect resistance in soybean.

Anteras de duas cultivares de soja foram cultivadas em meio de cultura basal B5 longo gelificado com agarose ou Phytagel®. Análises citológicas das anteras foram conduzidas durante os primeiros 45 dias de cultura para avaliar a viabilidade e o estágio de desenvolvimento dos micrósporos. A freqüência de formação de calos foi analisada após 45 dias do início da cultura. A análise da variância da viabilidade do micrósporo mostrou interações significativas de Cultivar X Agente Gelificante X Dias de Cultura. As freqüências de grãos de pólen viáveis diminuíram significativamente com o tempo de cultura, dentro de cada cultivar e agente gelificante testado. A interação Dia X Cultivar foi significante para as freqüências de grãos de pólen binucleados simétricos e estruturas multinucleados/multicelulares. O efeito do agente gelificante na freqüência de grãos de pólen binucleados simétricos e estruturas multinucleados/multicelulares não foi significante. Com relação às freqüências de calos e estruturas embriogênicas formadas, houve diferença significativa entre cultivares (IAS5= 14.8% e BRS 133=6.6%). O agente gelificante não mostrou efeito em tais freqüências.

Anthers of two soybean cultivars were cultured in B5 long basal culture media gelled with agarose or PhytagelTM. Cytological examinations of the anthers were carried out during the first 45 days of culture to assay the viability and developmental stage of microspores. Frequency of callus formation was recorded at 45 days of culture. The analysis of variance of the microspore viability assay showed significant Cultivar X Gelling Agent X Day of Culture interactions. The frequencies of viable microspores decreased significantly with time of culture, within each cultivar and gelling agent tested. The interaction Day X Cultivar was significant for the frequencies of binucleate symmetrical grains and multinucleate/multicellular structures. The effect of gelling agents on the frequency of binucleate symmetrical pollens grains and multinucleate/multicellular structures was not significant. About the frequencies of calli and embryogenic calli formed, a significant difference was detected between the cultivars (IAS5= 14.8% and BRS 133=6.6%). Gelling agents showed no effect over these frequencies.

Foi avaliado um método baseado em PCR do gene do RNAr 16S, desenvolvido com a finalidade de um diagnóstico molecular rápido na identificação das espécies filogeneticamente relacionadas Bradyrhizobium japonicum e B. elkanii, isoladas de nódulos de soja, visando ao seu emprego na identificação de estirpes mais competitivas e com maior capacidade de fixação de nitrogênio para uso na formulação de inoculantes comerciais. O método usado foi capaz de discriminar dez estirpes-padrão pertencentes a essas duas espécies de Bradyrhizobium, assim como identificar eficientemente 37 estirpes isoladas de lavouras cultivadas com soja.

A 16S rRNA gene PCR-based assay was developed aiming at a fast molecular diagnostic method to differentiate the two phylogenetically closely related species Bradyrhizobium japonicum and B. elkanii, isolated from soybean nodules, in order to identify those more competitive and comprising greater nitrogen fixation ability for use in the formulation of commercial inoculants. The assay used was able to discriminate ten reference strains belonging to these two Bradyrhizobium species, as well as to efficiently identify 37 strains isolated from fields cultivated with soybean.

Nas últimas três décadas, a pesquisa em embriogênese do micrósporo de soja restringiu-se ao cultivo in vitro de anteras, com inúmeras limitações, como o pequeno número de micrósporos responsivos e o alto potencial embriogênico dos tecidos esporofíticos. Por isso, foi executada uma seqüência de testes visando ao estabelecimento de condições adequadas para o isolamento e o cultivo in vitro de micrósporos e grãos de pólen, como um sistema alternativo ao cultivo de anteras. Inicialmente, uma técnica de isolamento foi desenvolvida usando botões florais de quatro cultivares de soja (Bragg, IAS 5, MG/BR-46 Conquista e BRSMT Uirapuru), a qual possibilitou o estabelecimento de cultivos com características e densidade satisfatórias. Posteriormente, diferentes condições de cultivo foram testadas. Apesar de os meios B5 e MS serem recomendados para o cultivo de anteras de soja, o melhor resultado foi obtido em meio PTA-15 modificado, como o aumento do tamanho dos micrósporos e a formação de 0,4% de grãos de pólen multicelulares na cultivar BRSMT Uirapuru.

In the last three decades, research on soybean microspore embryogenesis was restricted to anther culture, which presents limitations such as the small number of responsive microspores and the high embryogenic potential of sporophytic tissues. Therefore, a sequence of studies was performed to establish appropriate conditions for the isolation and culture of soybean microspores and pollen grains as an alternative to anther culture. First, a pollen and microspore isolation technique was developed using floral buds from four soybean cultivars (Bragg, IAS 5, MG/BR-46 Conquista and BRSMT Uirapuru). This technique allowed the establishment of cultures with satisfactory density and characteristics. Subsequently, different culture conditions were tested. Although B5 and MS media have been currently recommended for soybean anther culture, the best result was obtained in PTA-15 modified medium, with the formation of enlarged microspores and 0.4% of multicellular pollen grains in the cultivar BRSMT Uirapuru.

Embriões somáticos de soja em diferentes estádios de desenvolvimento, obtidos a partir de embriões zigóticos imaturos, foram estudados histologicamente com o objetivo de caracterizar as possíveis rotas ontogenéticas seguidas por esses embriões. Foram encontrados embriões nos estádios de proembrião, globular, cordiforme, torpedo e cotiledonar, revelando uma ontogenia similar àquela encontrada nos embriões zigóticos. Entretanto, a ausência de um suspensor definido, bem como o retardo no aparecimento de organização interna são diferenças marcantes entre esses dois processos embriogênicos. Além dessa rota de desenvolvimento, prováveis rotas alternativas de diferenciação são apresentadas.

Soybean somatic embryos obtained from immature zygotic embryos were histologically analyzed in order to determine possible ontogenetic routes followed by these embryos. The proembryo stage and globular, heart-shaped, torpedo and cotyledonary embryo stages were found, closely resembling the ontogeny of zygotic embryos. However, the absence of a characteristic suspensor as well as the delay in the establishment of inner organization were the main differences between these two embryogenic processes.

Foi avaliada a influência de diferentes tratamentos com antibióticos durante a transformação genética de soja. Inicialmente, desenvolveu-se um estudo para identificar como diferentes tratamentos com antibióticos afetam o tecido embriogênico da soja. O efeito da carbenicilina a 500 mg L-1 foi genótipo-dependente. Esse antibiótico não afetou a sobrevivência dos embriões da cv. IAS5, enquanto a proliferação dos embriões da cv. Bragg foi três vezes maior quando comparada com o controle. Por outro lado, cefotaxima, a 350 e 500 mg L-1, causou a morte dos tecidos embriogênicos de ambas as cultivares. Por fim, a associação de cefotaxima (250 mg L-1) + vancomicina (250 mg L-1) não afetou negativamente os embriões somáticos das cultivares testadas durante os 63 dias de tratamento. Posteriormente, foi realizado um segundo experimento para determinar a eficiência de diferentes tratamentos com antibióticos na supressão da linhagem LBA4404 de Agrobacterium tumefaciens durante a transformação genética. Nas condições da cultura, a carbenicilina, a 500 e 1000 mg L-1, não foi eficiente para a supressão de Agrobacterium. Por outro lado, os tratamentos com cefotaxima, 350 e 500 mg L-1, ou cefotaxima + vancomicina suprimiram eficientemente Agrobacterium após 49 dias. Os dados dos dois experimentos sugerem a cefotaxima + vancomicina por 49-63 dias como o tratamento mais apropriado. Esse é o primeiro registro do efeito de antibióticos sobre tecidos de soja. Foi identificada uma combinação de antibióticos que suprimiram A. tumefaciens com efeitos fitotóxicos mínimos, podendo ser recomendada para a otimização do método de transformação genética de soja mediada por Agrobacterium.

The influence of different antibiotic treatments in soybean genetic transformation was evaluated. First, an assay was performed to verify how different antibiotic treatments affect soybean embryogenic tissues. The effect of carbenicillin at 500 mg L-1 was genotype-dependent. This antibiotic did not affect embryo survival of cv. IAS5, but a three-fold increase of embryo proliferation was observed for cv. Bragg, when compared to the control. On the other hand, cefotaxime at 350 and 500 mg L-1 caused death of embryogenic tissues of both cultivars. Finally, the association of cefotaxime (250 mg L-1) + vancomycin (250 mg L-1) did not affect negatively the somatic embryos of tested cultivars until 63 days of treatment. Thereafter, a second experiment was carried out to determine the efficacy of different antibiotic treatments in suppressing LBA4404 Agrobacterium tumefaciens strain in genetic transformation. On tissue culture conditions, carbenicillin at 500 and 1000 mg L-1 was not active against Agrobacterium. On the other hand, treatments with cefotaxime at 350 and 500 mg L-1, and cefotaxime + vancomycin efficiently suppressed Agrobacterium during 49 days. Data of both experiments suggested cefotaxime + vancomycin for 49-63 days as the most appropriate treatment. This is the first work reporting the effect of antibiotics on soybean tissues. By identifying an antibiotic combination that suppressed A. tumefaciens with minimal phytotoxic effects, we are able to recommend it for improvement of soybean Agrobacterium-mediated transformation procedure.