Uma escala diagramática para a avaliação da severidade da seca-de-ponteiros do eucalipto causada por Erwinia psidii

This study aimed to develop and validate a standard area diagram (SAD) set to estimate the severity of bacterial blight of eucalyptus caused by Erwinia psidii. For this purpose, an eightlevel SAD was developed and validated by ten inexperienced raters. Accuracy and precision of the estimates by each rater, with and without the SAD, were determined based on Lin’s concordance correlation coefficient. The proposed SAD improved the accuracy and precision of the estimates. The SAD set studied here is a useful tool in assessments of bacterial blight of eucalyptus for epidemiological research and breeding programs.Este trabalho objetivou o desenvolvimento de uma escala para estimar a severidade da seca-de-ponteiros do eucalipto causada por Erwinia psidii. Para isso, uma escala de oito níveis foi desenvolvida e validada por dez avaliadores inexperientes. A acurácia e precisão das estimativas de cada avaliador, com e sem a escala, foram determinadas baseadas no coeficiente de correlação concordante de Lin. A escala proposta melhorou a acurácia e a precisão das estimativas. A escala estudada se mostrou uma ferramenta útil na avaliação da seca-de-ponteiros do eucalipto para estudos epidemiológicos e em programas de melhoramento

Endophytic bacteria Bacillus safensis and Pseudomonas hibiscicola and their ability to increase rice seedling growth

Endophytic bacteria Bacillus safensis RS95 and Pseudomonas hibiscicola RS121 were evaluated for their ability to promote the growth of rice seedlings and produce indole-acetic acid (IAA) and siderophores and to solubilize phosphates. ‘Guri’ rice seeds were immersed in bacterial endophyte cell suspensions (separated and two-strain mixed), as well as in Escherichia coli DH5α, phosphate-buffered saline (PBS) and water treatments (negative controls). Seeds were sown on agar-water in Petri plates placed vertically at an angle of 65°. The ability of plant growth-promoting endophytic bacteria (PGPEB) to produce IAA and siderophores was determined by Salkowski colorimetric and chrome azurol S (CAS) assays, respectively. Mineral phosphate solubilization activity was calculated by inoculating the endophytes onto medium containing insoluble phosphate. PGPEB showed a positive effect on the growth of rice seedlings, causing a mean growth of shoots and primary-roots of 60 and 67%, respectively. Bacterial strains also showed positive traits for IAA and siderophore production, as well as phosphate-solubilization activity

Biocontrole da mancha-bacteriana e da pinta-preta por bactérias epifíticas em tomateiro

The objective of this work was to evaluate in vitro and in vivo biocontrol of Xanthomonas vesicatoria) and early blight (Alternaria solani) by the epiphytic bacteria Paenibacillus macerans and Bacillus pumilus. Tomato plants were previously sprayed with epiphytic bacteria, benzalkonium chloride and PBS buffer and, after four days, they were inoculated with A. solani and X. vesicatoria. To determine the phytopathogenic bacteria population, leaflet samples were collected from each treatment every 24 hours, for seven days, and plated on semi-selective medium. The effect of epiphytic bacteria over phytopathogens was performed by the antibiosis test and antagonistic activity measured by inhibition zone diameter. The epiphytic and benzalkonium chloride drastically reduced the severity of early blight and bacterial spot in comparison to the control (PBS). In detached leaflets, the epiphytic bacteria reduced in 70% the number of phytopathogenic bacteria cells in the phylloplane. The antibiosis test showed that the epiphytic bacteria efficiently inhibit the phytopathogens growth. In all the bioassays, the epiphytic bacteria protect tomato plants against the phytopathogens.  O objetivo deste trabalho foi avaliar o biocontrole in vitro e in vivo dos fitopatógenos mancha-bacteriana (Xanthomonas vesicatoria) e pinta-preta (Alternaria solani) pelas bactérias epifíticas Paenibacillus macerans e Bacillus pumilus. Plantas de tomate foram previamente pulverizadas com as bactérias epifíticas, cloreto de benzalcônio e tampão PBS e, após quatro dias, receberam inoculação com A. solani e X. vesicatoria. A fim de determinar a população da bactéria fitopatogênica, amostras de folíolos foram coletadas de cada tratamento em intervalos de 24 horas, durante sete dias, e inoculadas em meio semisseletivo. O efeito das bactérias epifíticas sobre os fitopatógenos foi realizado pelo teste de antibiose e atividade antagônica avaliada pelo diâmetro da zona de inibição. As bactérias epifíticas e o cloreto de benzalcônico reduziram drasticamente a severidade da pinta-preta e da mancha-bacteriana, comparado com o controle (PBS). Em folíolos destacados, as bactérias epifíticas reduziram em até 70% o número de células da bactéria fitopatogênica no filoplano. As bactérias epifíticas inibem eficientemente o crescimento dos fitopatógenos em meio de cultura. Em todos os bioensaios, as bactérias epifíticas protegem as plantas de tomate contra os fitopatógenos

Controle biológico mediado por Bacillus subtilis

O emprego de microrganismos para fins de controle biológico de fitomoléstias vem sendo amplamente estudado no mundo. Neste contexto, o uso de procariotos como bons agentes antagônicos contra fitopatógenos tem se mostrado uma alternativa crescente e inteligente no manejo integrado de doenças. Adicionalmente, muitos estudos vêm sendo realizados com Bacillus subtilis, bactéria habitante natural do solo. A bactéria pode colonizar todos os órgãos vegetativos da planta, sendo encontrada como epifítica, endofítica e rizobactéria, confirmando o seu amplo espectro para o uso agronômico. Assim, esta revisão tem por finalidade levantar as recentes pesquisas sobre Bacillus subtilis como bom agente de biocontrole.Palavras-chave: bactéria epifítica, rizobactéria, bactéria endofítica, indução de resistência, bioproduto.

Induced defense responses in tomato against bacterial spot by proteins synthesized by endophytic bacteria

Some endophytes can synthesize molecules that elicit the induction of plant resistance to infection by pathogens. The objective of this study was to demonstrate that protein fractions 42 and 75 from Bacillus amyloliquefaciens and Bacillus pumilus were capable of acting as elicitors of induced resistance in tomato plants against Xanthomonas vesicatoria, following partial resolution by gel-filtration chromatography. Tomato plants sprayed with protein fractions 42 and 75 reduced, respectively, 63.5 and 56.6% of bacterial spot, compared with control plants. Additionally, these fractions promoted the increase of peroxidase (POX) and polyphenol oxidase (PPO) enzyme activities in treated plants. In SDS-PAGE stained with silver nitrate, protein fractions 42 and 75 appeared as simple bands with estimated molecular mass of 28 and 43 kDa, respectively. We report the partial characterization of two macromolecules synthesized by endophytic bacteria that act as elicitors of systemic resistance in tomato against X. vesicatoria