ABSTRACT 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.

RESUMO 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.

ABSTRACT 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 eight-level 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.

ABSTRACT Powdery mildew is one of the main diseases in eucalyptus clonal nursery. The present work aimed to confirm the identity of the causal agent of powdery mildew in clonal seedlings of Eucalyptus spp., and to evaluate the susceptibility reaction of clones to this disease. Conidia were collected in minigardens for molecular identification of the pathogen. We assessed susceptibility by testing 4 clones: Clone 1 (Eucalyptus benthamii ), Clone 2 (E. dunni), Clone 3 (E. benthamii) and Clone 4 (E. urophylla x E. globulus). Scale of classes was used for calculations of Disease Index (DI) and Final Incidence (I). Temporal analysis was performed using the Logistic and Gompertz models. The molecular identification confirmed the identity of the isolates approximate to Podosphaera pannosa (teleomorphic phase of Oidium eucalypti). The Gompertz model obtained a better adjustment to the severity and incidence data, and clones 1 and 2 showed greater susceptibility to eucalyptus powdery mildew.

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.

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

The objective of this work was to evaluate in vitro and in vivo biocontrol of bacterial spot (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 isolado UFV-101 foi selecionado em ensaios prévios como promotor de crescimento e indutor de resistência. O sobrenadante, advindo do cultivo desse microrganismo em meio líquido, demonstrou a capacidade de induzir resistência em tomateiro contra os patógenos Pseudomonas syringae pv. tomato, Xanthomonas vesicatoria, Alternaria solani e Corynespora cassiicola. Neste trabalho, a bactéria foi cultivada em meio mínimo por 48 h e as células precipitadas por centrifugação. O sobrenadante, depois de concentrado por liofilização, foi dializado em membrana com ponto de corte 12 kDa e fracionado em coluna contendo Sephadex G25 equilibrada em tampão PBS. As frações correspondentes ao pico protéico foram aplicadas em mudas de tomateiro. Depois de quatro dias foram coletados folíolos e inoculados com o patógeno desafiador. Folíolos expostos ao sobrenadante da bactéria apresentaram número de lesões semelhantes a aqueles expostos ao acibenzolar-S-methyl e em número inferior a aqueles tratados com água. Desta forma, neste trabalho, a natureza protéica do sobrenadante foi confirmada, bem como, sua atividade indutora de resistência contra o patógeno C. cassiicola.

Isolate UFV-101 of Bacillus cereus was selected in previous studies for promoting growth inducing resistance in plants. In a previous study, supernatant from cultures of the microorganism in a liquid medium was found to induce resistance in tomato foliage against the pathogens Pseudomonas syringae pv. tomato, Xanthomonas vesicatoria, Alternaria solani and Corynespora cassiicola. In the present work the microorganism was grown in a minimal medium for 48 h and the cells precipitated for centrifugation. The supernatant was concentrated by lyophilization, dialyzed in a 12 kDa cut-off point membrane and fractioned in column containing Sephadex G25 balanced in PBS buffer. The fractions corresponding to a protein peak were applied to tomato seedlings. After four days leaflets were collected and inoculated with the pathogen. C. cassiicola. The numbers of lesions produced by the pathogen on leaflets exposed to the bacterial supernatant were similar to those exposed to acibenzolar-S-methyl but fewer than in those treated with water. It is concluded that the supernatant contained protein which induced resistance in the tomato leaves against C. cassiicola.

Dois antagonistas selecionados para o biocontrole da vassoura-de-bruxa do cacaueiro foram avaliados quanto à capacidade em ativar mecanismos de defesa de plantas contra patógenos. Para tanto, mudas seminais de cacaueiro "comum" foram cultivadas em casa-de-vegetação por 30 dias e expostas aos antagonistas aplicados a mudas de cacaueiro por atomização, individualmente e em associação. O primeiro par de folhas das mudas dos diferentes tratamentos foi coletado aos dois, quatro, 12 e 24 dias após a exposição aos antagonistas. Foi quantificada a atividade de peroxidases, polifenoloxidases, quitinases e beta-1,3-glucanases no material coletado. Observou-se um aumento na atividade de peroxidases e polifenoloxidases nos primeiros dias após a exposição das mudas, especialmente ao isolado Ac26. Não foi observado efeito aditivo ou sinergístico nas mudas expostas aos dois isolados simultaneamente.

Two antagonists selected for the biocontrol of cocoa witches' broom were investigated for their ability in triggering increases in the activity of enzymes associated to induced resistance. In a greenhouse, thirty days old cocoa seedlings were exposed t antagonists by spraying a propagule suspension of every antagonist or a mixture of them. At two, four 12 and 24 days exposing plants to the antagonists, the first leaf pair of every plant was excised and used for quantifying the activity of peroxidases, poly-phenol-oxidases, chitinases and beta-1,3-glucanases. There were increases in activity of peroxidases, poly-phenol-oxidases, mainly in the case of isolate Ac26. Additive or synergistic effects were not observed as a consequence of exposing plants to both antagonists together.