ABSTRACT Mangroves are ecosystems located in the transition zone between land and sea that serve as a potential source of biotechnological resources. Brazil's extensive coast contains one of the largest mangrove forests in the world (encompassing an area of 25,000 km2 along all the coast). Endophytic bacteria were isolated from the following three plant species: Rhizophora mangle, Laguncularia racemosa and Avicennia nitida. A large number of these isolates, 115 in total, were evaluated for their ability to fix nitrogen and solubilize phosphorous. Bacteria that tested positive for both of these tests were examined further to determine their level of indole acetic acid production. Two strains with high indole acetic acid production were selected for use as inoculants for reforestation trees, and then the growth of the plants was evaluated under field conditions. The bacterium Pseudomonas fluorescens (strain MCR1.10) had a low phosphorus solubilization index, while this index was higher in the other strain used, Enterobacter sp. (strain MCR1.48). We used the reforestation tree Acacia polyphylla. The results indicate that inoculation with the MCR1.48 endophyte increases Acacia polyphylla shoot dry mass, demonstrating that this strain effectively promotes the plant's growth and fitness, which can be used in the seedling production of this tree. Therefore, we successfully screened the biotechnological potential of endophyte isolates from mangrove, with a focus on plant growth promotion, and selected a strain able to provide limited nutrients and hormones for in plant growth.

Abstract The bacterium Xylella fastidiosa is the causal agent of citrus variegated chlorosis (CVC) and has been associated with important losses in commercial orchards of all sweet orange [Citrus sinensis (L.)] cultivars. The development of this disease depends on the environmental conditions, including the endophytic microbial community associated with the host plant. Previous studies have shown that X. fastidiosa interacts with the endophytic community in xylem vessels as well as in the insect vector, resulting in a lower bacterial population and reduced CVC symptoms. The citrus endophytic bacterium Methylobacterium mesophilicum can trigger X. fastidiosa response in vitro, which results in reduced growth and induction of genes associated with energy production, stress, transport, and motility, indicating that X. fastidiosa has an adaptive response to M. mesophilicum. Although this response may result in reduced CVC symptoms, the colonization rate of the endophytic bacteria should be considered in studies that intend to use this endophyte to suppress CVC disease. Symbiotic control is a new strategy that uses symbiotic endophytes as biological control agents to antagonize or displace pathogens. Candidate endophytes for symbiotic control of CVC must occupy the xylem of host plants and attach to the precibarium of sharpshooter insects to access the pathogen. In the present review, we focus on interactions between endophytic bacteria from sweet orange plants and X. fastidiosa, especially those that may be candidates for control of CVC.

O objetivo deste trabalho foi isolar, caracterizar e identificar a comunidade bacteriana endofítica de sementes de soja e avaliar o seu potencial biotecnológico. Foram utilizadas sementes de 12 cultivares de soja. Os isolados bacterianos endofíticos obtidos foram avaliados in vitro quanto ao antagonismo a fungos fitopatogênicos, síntese de ácido indolacético (AIA) e solubilização de fosfato. A caracterização foi realizada com técnicas de isolamento, análise de restrição do DNA ribossomal amplificado (ARDRA) e sequenciamento parcial do gene 16S rDNA. Os isolados com maior potencial biotecnológico foram inoculados em sementes de soja, para se avaliar a capacidade de promoção de crescimento de plantas. Foi possível identificar 12 ribótipos por meio da ARDRA, que foram classificados como: Acinetobacter, Bacillus, Brevibacterium, Chryseobacterium, Citrobacter, Curtobacterium, Enterobacter, Methylobacterium, Microbacterium, Micromonospora, Pantoea, Paenibacillus, Pseudomonas, Ochrobactrum, Streptomyces e Tsukamurella. Quanto ao potencial biotecnológico da comunidade, 18% dos isolados controlaram o crescimento de fungos fitopatogênicos, 100% produziram AIA, e 39% solubilizaram fosfato. O isolado 67A(57) de Enterobacter sp. aumentou significativamente a massa de matéria seca da raiz. A inoculação de isolados com elevado potencial biotecnológico em avaliações in vitro não promoveu o crescimento de plantas de soja na maioria dos casos.

The objectives of this work were to isolate, characterize and identify the endophytic bacterial community of soybean seeds, and to test the biotechnological potential of this community. Seeds from 12 soybean cultivars were used. The endophytic bacterial isolates were evaluated for in vitro antagonism against phytopathogenic fungi, synthesis of indoleacetic acid (IAA), and capacity to solubilize phosphate. Isolation techniques, amplified ribosomal DNA restriction analysis (ARDRA) grouping, and identification by means of partially sequencing the 16S rDNA were used in community characterization. The isolates with best biotechnological potential were inoculated in seeds to evaluate their ability to promote plant growth. Twelve ribotypes were identify by means of ARDRA and classified as: Acinetobacter, Bacillus, Brevibacterium, Chryseobacterium, Citrobacter, Curtobacterium, Enterobacter, Methylobacterium, Microbacterium, Micromonospora, Pantoea, Paenibacillus, Pseudomonas, Ochrobactrum, Streptomyces and Tsukamurella. As for the biotechnological potential of the community, 18% of the isolates were able to antagonize phytopathogenic fungi, 100% to synthesize IAA, and 39% to solubilize phosphate. The strain 67A(57) of Enterobacter sp. increased significantly the dry root biomass. Inoculation of promising isolates did not promote growth in soybean plants in most of the cases.

O objetivo deste trabalho foi estudar a produção de sideróforos pelas bactérias endofíticas Methylobacterium spp., que ocupam o mesmo nicho ecológico que Xylella fastidiosa subsp. pauca (Xfp), em plantas cítricas. A produção de sideróforos, pelas linhagens de Methylobacterium, foi testada por meio do ensaio de cromoazarol-ágar (chromeazurol agar assay-CAS), teste de Csáky (tipo hidroxamato) e do teste de Arnow (tipo catecol). Além disso, a habilidade de Xfp em utilizar sideróforos produzidos por bactérias endofíticas, como fonte de ferro, in vitro, foi avaliada. Todas as 37 linhagens de Methylobacterium spp. testadas foram positivas para a produção de sideróforos, pelo teste CAS-ágar. Methylobacterium spp. foram capazes de produzir sideróforos do tipo hidroxamato, mas não do tipo catecol. O crescimento in vitro de Xfp foi estimulado pela presença de sideróforos no sobrenadante de Methylobacterium mesophilicum endofítica.

The objective of this work was to study the production of siderophores by endophytic bacteria Methylobacterium spp., which occupy the same ecological niche as Xylella fastidiosa subsp. pauca (Xfp) in citrus plants. The siderophore production of Methylobacterium strains was tested according to chromeazurol agar assay test (CAS), Csáky test (hydroxamate-type) and Arnow test (catechol-type). In addition, the ability of Xfp to use siderophores, in vitro, produced by endophytic bacteria as source of iron, was evaluated. All 37 strains of Methylobacterium spp. tested were CAS-positive for siderophore production. Methylobacterium spp. produced hydroxamate-type, but not catechol-type siderophores. In vitro growth of Xfp was stimulated by the presence of supernatant siderophores of endophytic Methylobacterium mesophilicum.

A Clorose Variegada dos Citros (CVC) é uma doença economicamente importante e destrutiva no Brasil e é causada pela bactéria Xylella fastidiosa e transmitida por insetos vetores tal como Oncometopia facialis. Nesse estudo, a eficácia do fungo Metarhizium anisopliae em controlar o inseto vetor O. facialis foi estudada em condições de bioensaio. Nesse bioensaio, insetos foram pulverizados com uma suspensão de 5 X 10(7) conídio mL-1. Insetos-adultos capturados no campo foram tratados em grupos de 10, em um total de 11 replicatas por tratamento. Diferenças significativas entre a mortalidade natural e a mortalidade dos insetos tratados com o fungo foram observadas em 6 dias após a inoculação (P<0.05). Estas diferenças significativas aumentaram antes do décimo dia após o tratamento. O fungo causou uma mortalidade de 87,1%, com uma LT50 variando entre 5 e 6 dias. A LC50 foi de 1,2 X 10(6) conídio mL-1, variando de 7,7 X 10(5) a 2 X 10(6) conídio mL-1. Estes resultados mostraram que o vetor O. facialis foi susceptível a ação entomopatogênica de M. anisopliae em condições controladas durante o bioensaio.

Citrus Variegated Chlorosis (CVC) is an economically important, destructive disease in Brazil and is caused by Xylella fastidiosa and transmitted by sharpshooter insects. In this study, the efficacy of the fungus Metarhizium anisopliae in controlling the sharpshooter Oncometopia facialis was studied by bioassay conditions. In the bioassay, insects were sprayed with a suspension containing 5 X 10(7) conidia mL-1. Adults captured in the field were treated in groups of 10 in a total of 11 replications per treatment. Significant differences between the natural mortality and the mortality of insects treated with the fungus were observed 6 days after inoculations (P<0.05). These significant differences increased until 10 days after treatment. The fungus caused 87.1% mortality, with the LT50 varying from 5 to 6 days. The LC50 was 1.2 X 10(6) conidia mL-1, varying from 7.7 X 10(5) to 2 X 10(6) conidia mL-1. The results showed that the sharpshooter O. facialis was susceptible to the entomopathogenic action of M. anisopliae in controlled condition during bioassay.

O objetivo deste trabalho foi avaliar o efeito da aplicação do benzotiadiazole (BTH) e do silício sobre o controle da doença causada pela Xylella fastidiosa subsp. pauca em Nicotiana tabacum. Os experimentos foram conduzidos em condições de casa de vegetação, onde as plantas de N. tabacum receberam inoculação de X. fastidiosa (linhagem 9a5c) com 4,7x10(7) UFC mL-1. Os tratamentos consistiram da pulverização das folhas, com soluções de BTH (0,6 e 1,2 mM), e aplicação ao solo de soluções de metassilicato de sódio (2 e 4 µM de Si). Cinco plantas foram utilizadas, por tratamento. Plantas de N. tabacum tratadas com BTH não demonstraram redução de sintomas da bacteriose. Entretanto, plantas tratadas com metassilicato de sódio, sim. A indução de resistência pelo Si poderá ser útil no controle da clorose variegada dos citros.

The objective of this work was to evaluate the effects of benzothiadiazole (BTH) and silicon applications on the control of the disease caused by Xylella fastidiosa subsp. pauca on Nicotiana tabacum. The experiments were carried out under greenhouse conditions, where X. fastidiosa (9a5c strain) containing 4.7x10(7) CFU mL-1 was inoculated in N. tabacum plants. The BTH and silicon treatments consisted of BTH (0.6 and 1.2 mM) application to plant leaves, and sodium metasilicate solution (2 and 4 µM of Si) application to soil. Plants of N. tabacum treated with BTH showed no reduction in symptoms. However, plants treated with sodium metasilicate (source of Si) were rendered asymptomatic. Disease resistance induced by Si can be useful to control citrus variegated chlorosis.

O objetivo deste trabalho foi caracterizar a comunidade bacteriana endofítica de plantas assintomáticas (escapes) e afetadas pela clorose variegada dos citros (CVC) por meio de isolamento em meio de cultura, técnica de gradiente desnaturante em gel de eletroforese (DGGE) e detecção de Methylobacterium mesophilicum e Xyllela fastidiosa por meio de PCR específico, para estudar esta comunidade e sua relação com a ocorrência da CVC. A análise da comunidade bacteriana via DGGE permitiu a detecção de X. fastidiosa, bem como Klebsiella sp. e Acinetobacter sp. como endófitos de citros. Foram observados também Curtobacterium sp., Pseudomonas sp., Enterobacter sp. e Bacillus spp. Utilizando primers específicos, Methylobacterium mesophilicum e X. fastidiosa também foram observadas, reforçando hipóteses de que estas bactérias podem estar interagindo no interior da planta hospedeira.

The aim of this work was to characterize endophytic bacterial community of assintomatic (escape) and Citrus Variegated Chlorosis (CVC)-affected citrus plants using isolation in culture medium, denaturing gradient gel electrophoresis (DGGE) technique and Methylobacterium mesophilicum as well as Xylella fastidiosa specific PCR, allowing to assess this community and its interactions with CVC. The study of bacterial community by DGGE analysis allowed the detection of X. fastidiosa, as well as Klebsiella sp. e Acinetobacter sp., which were not detected previously. Curtobacterium sp., Pseudomonas sp., Enterobacter sp. and Bacillus spp. were also observed as endophyte in citrus plants. Using specific primers Methylobacterium mesophilicum and X. fastidiosa were observed, reinforcing that these bacteria could interact inside the host plant.