José Rogério de Oliveira

Etiology of bacterial leaf blight of eucalyptus in Brazil

Bacterial leaf blight of eucalyptus is initially characterized by water soaked, angular, amphigenous and interveinal lesions, concentrated along the main vein, at the edges or scattered on the leaf blade. As the disease progresses, the lesions become brown to pale, and when young leaves are infected leaf cut areas at the edges or perforations at the center of the lesions may appear due to abortion of the necrotic area. Eventually, necrosis may be found on petiole and twigs. Leaf fall commonly occurs on highly susceptible genotypes due to the early senescence of diseased leaves. Precise diagnosis is accomplished by bacterial exudation from leaf sections placed in a water drop under light microscope (200 x). Twenty-five bacterial isolates from Amapa (2), Bahia (4), Minas Gerais (2), Sao Paulo (9), Para (3), Mato Grosso do Sul (1), and Rio Grande do Sul (4) States, which induced hypersensitive reaction (HR) in non-host plants and were pathogenic to eucalyptus, when inoculated by inoculum injection, were identified by biochemical assays, using carbon sources (MicroLogTM BIOLOG) and sequence analysis (16S rDNA). Ten isolates were identified as Xanthomonas axonopodis, four as X. campestris, four as Pseudomonas syringae, two as P. putida, two as P. cichorii, one as Erwinia sp., and two were similar to bacterial genera of Rhizobiaceae. When spray inoculated on intact plants of eucalyptus, only X. axonopodis, P. cichorii and isolates of the Rhizobiaceae family induced typical symptoms of the disease and were considered pathogenic. In Brazil, X. axonopodis seems to be the most widespread species causing the bacterial leaf blight of Eucalyptus spp.

Rhizobacteria induces resistance against Fusarium wilt of tomato by increasing the activity of defense enzymes

Fusarium wilt, caused by Fusarium oxysporum f.sp. lycopersici (Fol), is one of the most important diseases that affect tomato yield worldwide. This study investigated the potential of three antagonists, Streptomyces setonii (UFV 618), Bacillus cereus (UFV 592) and Serratia marcescens (UFV 252), and as positive control the hormone jasmonic acid (JA), to reduce Fusarium wilt symptoms and to potentiate the defense enzymes in the stem tissues of tomato plants infected by Fol. The seeds were microbiolized with each antagonist, and the soil was also drenched with them. The plants were sprayed with JA 48 h before Fol inoculation. The area under the Fusarium wilt index progress curve was reduced by 54, 48, 47 and 45% for the UFV 618, JA, UFV 592 and UFV 252 treatments, respectively. The three antagonists, and even the JA spray, efficiently reduced the Fusarium wilt symptoms on the tomato plant stems, which can be explained by the lower malondialdehyde concentration (an indication of oxidative damage to lipids in the plasma membranes) and the greater activities of peroxidases, polyphenoloxidases, glucanases, chitinases, phenylalanine ammonia-lyases and lipoxygenases, which are commonly involved in host resistance against fungal diseases. These results present a novel alternative that can be used in the integrated management of Fusarium wilt on tomatoes.

Silicon reduces bacterial speck development on tomato leaves

This study aimed to evaluate the effect of silicon (Si) on the resistance of tomato plants (cv. Santa Clara) to bacterial speck, caused by Pseudomonas syringae pv. tomato (Pst). Tomatoes were grown in soil without calcium silicate (control), in soil without calcium silicate and sprayed with Supa Silica® (2 mL/L) (SS) and in soil with calcium silicate (0.16 g/kg of soil) (CS). The effect of SS on the growth of Pst was evaluated in vitro. There was no significant difference among the treatments for foliar Si concentration and incubation period. No significant differences were observed between the control and CS for the number of lesions per plant (NLP) and bacterial speck severity estimated by the software QUANT. The NLP was significantly reduced with SS spray. There was a negative linear response of in vitro Pst growth to the SS rates. Peroxidase, polyphenoloxidase and glucanase activities were significantly higher for plants sprayed with SS and grown in soil with CS compared to the control treatment. Phenylalanine ammonia-lyase and lypoxygenase activities were significantly higher for plants grown in soil with CS compared to the control. The concentration of malondialdehyde was significantly higher for plants sprayed with SS compared to the control at 0 and 7 dai. The results of this study indicate that the symptoms of bacterial speck are reduced when plants are sprayed with SS, which can be linked to the direct effect of this product against Pst rather than the potentation of host defense responses.

Fungi and bacteria associated with post-harvest rot of ginger rhizomes in Espírito Santo, Brazil

The objective of this study was to identify fungi and bacteria associated with the post-harvest rot of ginger rhizomes (Zingiber officinale Roscoe) in the Serrana region of Espirito Santo, Brazil. Rhizomes with symptoms of rot were sampled in the packing-house and in the field soon after harvest. In the packing-house, we report positive pathogenicity tests for Acremonium murorum, Acrostalagmus luteo-albus, Fusarium sp., Fusarium oxysporum, Lasiodiplodia theobromae and Sclerotium rolfsii. For the rhizomes sampled during harvest, the mean incidence of pathogens was as follows: F. oxysporum, 74%; Fusarium sp., 31%; Fusarium solani, 21%; Nigrospora oryzae, 5%; Fusarium semitectum and Nigrospora sphaerica, 6%; Alternaria tenuissima, 4%; Penicillium commune, Verticillium sp.(1) and Verticillium sp.(2), 3%; A. luteo-albus, Aspergillus niger, Chaetomium sp. and Epicoccum sp., 2%; and Curvularia geniculata and Mucor hiemalis, 1%. The mean incidence of bacteria that cause soft rot was as follows: Enterobacter cloacae subsp. cloacae, 4%; and Pseudomonas fluorescens, 1%. The presence of Enterobacter cloacae subsp. cloacae indicated probable fecal contamination. This is the first record of ginger rhizome rot caused by P. fluorescens in the world and the first from A. murorum, A. luteo-albus, L. theobromae and E. cloacae subsp. cloacae causing ginger rhizome rot in Brazil.

Intervals and Number of Applications of Acibenzolar-S-Methyl for the Control of Bacterial Spot on Processing Tomato

Acibenzolar-S-methyl (ASM) is a plant activator that triggers systemic acquired resistance that is labeled for use in Brazil for managing tomato bacterial spot. The aim of this study was to define the optimum relationship between interval and number of applications of ASM for the most efficacious control of bacterial spot on processing tomato. Four intervals between applications (4, 7, 10, and 14 days) and four application frequencies (4, 6, 8, and 10 applications) were evaluated in five trials performed between 2010 and 2011 in Brasília, Distrito Federal, and in Morrinhos, in the state of Goiás. Copper hydroxide (CH) was applied after ASM applications to complete 13 applications per growing season. Two check treatments were added: standard CH weekly applications and untreated. The following variables were evaluated: severity of bacterial spot, yield, percentage of ripe and rotten fruit, soluble solids content, and the benefit/cost ratio. Disease severity varied between treatments in three trials and yield varied in two trials. A greater number of applications resulted in a reduction of bacterial spot, and the ideal interval between applications was between 8 to 10 days. However, there was a reduction in yield with 10 ASM applications. The temporal effect of ASM applications on bacterial spot severity was evaluated under greenhouse conditions. Reduction in disease severity was observed up to 6 days following ASM application. Additionally, the weekly treatment of seven applications of ASM followed by six applications of CH was compared with a standard program of CH under commercial production conditions in Itaberaí, Goiás, where bacterial spot occurred naturally. The program with ASM and CH resulted in significantly less foliar disease severity than the standard program, which did not result in yield gains. In addition, no differences were detected between the two programs for soluble solids content, industrial yield, plant height, and percentage of ripe and rotten fruit.

Antagonistic rhizobacteria and jasmonic acid induce resistance against tomato bacterial spot

Tomato bacterial spot on tomato may be caused by four species of Xanthomonas and among them X. gardneri (Xg) is the most destructive one, especially in areas irrigated using a center pivot system in Minas Gerais state and the midwest region of Brazil. Due to the ineffectiveness of chemical control and the lack of cultivars with high levels of genetic resistance, this study investigated the potential of three antagonists (Streptomyces setonii (UFV618), Bacillus cereus (UFV592) and Serratia marcescens (UFV252)), and the hormone jasmonic acid (JA) as a positive control, to reduce bacterial spot symptoms and to potentiate defense enzymes in the leaves of tomato plants infected by Xg. Tomato seeds were microbiolized with each antagonist, and the soil was drenched with these bacteria. The plants were sprayed with JA 48 h before Xg inoculation. The final average severity on the tomato plants was reduced by 29.44, 59.26 and 61.33% in the UFV592, UFV618 and JA treatments, respectively. The UFV618 antagonist was as effective as JA in reducing bacterial spot symptoms on tomatoes, which can be explained by the greater activities of defense enzymes that are commonly involved in host resistance against bacterial diseases. These results suggest that JA and the UFV618 antagonist can be used in the integrated management of bacterial spot on tomatoes.

Obtenção de bactérias para a o biocontrole de Meloidogyne javanica por meio de aquecimento de solo e tratamento com filtrado de raízes de plantas antagonistas a fitonematóides

Five samples of 1 kg each of organic soil (10.14 dag/kg) were autoclaved at 120 °C for 1 hour, five were heated in a 660 watt and 2450 Hz microwave oven at full power for 4 min, and five were not heat-treated. Roots of Mucuna aterrima, Crotalaria juncea, Tagetes erecta and Lycopersicon esculentum were macerated, separately, in 1000 ml of tap water in a blender at low speed for 30 s, then sieved. Each of the resulting suspensions or just tap water (control treatment) was poured on one of the different soil samples inside a plastic bag and stored at 28 °C for 24 h. Seventy-eight bacterial isolates were obtained from the soil samples by serial dilution and selected for a subsequent assay for the biocontrol of Meloidogyne javanica. Tomato seeds were soaked in suspension of each bacterial isolate, then sowed in substrate inside plastic tubes in the greenhouse. The seedlings were each inoculated with 400 eggs of the nematode. The isolate UFV-6 of Escherichia coli reduced the number of galls to the highest extent (80%), and UFV-8 of Citrobacter freundii was the most effective in reducing number of eggs (83%). The identification of the isolates was done by fatty acid analyses and biochemical tests.

Host specificity in interaction Xanthomonas campestris pv. campestris - brassicas.

Face as escassas informacoes acerca da variabilidade patogenica de isolados brasileiros de Xanthomonas campestris pv. campestris, realizou-se um estudo para avaliar a especificidade patogenica de trinta e tres isolados do patogeno, provenientes de varias regioes do Brasil e do exterior, a oito especies de brassicas, atraves de inoculacao por meio de injecao da suspensao bacteriana nas folhas. Desse total, 12 isolados foram obtidos de couve-comum (Brassica oleracea var. acephala), nove de repolho (B. oleracea var. capitata), cinco de couve-flor (B. oleracea var. botrytis), dois de canola (B. napus), um de brocolos (B. oleracea var. italica), um de couve-chinesa (B. chinensis), um de couve-rabano (B. oleracea var. gongylodes) e dois de rabanete (Raphanus sativus). A avaliacao da patogenicidade dos isolados da bacteria, frente aos hospedeiros em estudo, demonstrou que 14 deles nao apresentaram especificidade, originando sintomas em todas as diferentes plantas inoculadas. Os 19 isolados restantes, entretanto, apresentaram relativo grau de especificidade, nao causando doenca em uma ou mais das plantas inoculadas.

Eliminação de Clavibacter michiganensis subsp. michiganensis em estacas de bambu infestadas artificialmente

Different treatments were compared as a means to eradicate viable cells of Clavibacter michiganensis subsp. michiganensis from infested bamboo stakes. The soaking of the stakes, for 30 minutes, in a 2% solution of sodium hypochlorite was the most efficient treatment, as compared to solarization with or without a plastic mulch and fumigation with phosfine or methyl bromide.

Volume de aplicação e eficiência do controle químico da mancha bacteriana em tomateiro industrial

Hortic. bras., Brasília, v.35, n.3, July-September 2017 N Brasil, a cultura do tomate para processamento industrial vem crescendo, resultado do aumento da demanda dos derivados de tomate (Melo & Fonte, 2011). A produção brasileira nesse segmento concentra-se no estado de Goiás, onde as condições de clima, solo e topografia favorecem o cultivo (Silva-Junior et al., 2015). Nessa região, irrigam-se os cultivos de tomate para processamento por aspersão via pivôcentral, o que favorece a ocorrência de doenças que comprometem a produtividade e a qualidade dos frutos, com destaque para a mancha bacteriana (Quezado-Duval et al., 2004). Essa doença está associada a quatro espécies do gênero Xanthomonas: X. euvesicatoria, X. gardneri, X. perforans e X. vesicatoria. Nas principais regiões produtoras do Brasil, os primeiros estudos de epidemias da mancha bacteriana em tomate para processamento indicavam a prevalência da espécie X. gardneri (Quezado-Duval et al., 2004). Entretanto, segundo levantamentos mais recentes, a ocorrência de X. perforans tem aumentado e passou a prevalecer nos campos de tomate para processamento na região central do país (Araújo et al., 2016). Essas bactérias podem sobreviver em restos culturais, sementes, plantas daninhas e plantas voluntárias (Quezado-Duval & Lopes, 2010), o que dificulta a eliminação das fontes de inóculo. Até o momento, não há variedades comerciais desse segmento com níveis efetivos de resistência (Quezado-Duval et al., 2014). Assim, a ferramenta mais utilizada pelos produtores para o manejo da mancha bacteriana tem sido o controle químico. PONTES, NC; NASCIMENTO, AR; GOLYNSKI, A; MOITA, AW; MAFFIA, LA; OLIVEIRA, JR; QUEZADO-DUVAL, AM. 2017. Volume de aplicação e eficiência do controle químico da mancha bacteriana em tomateiro industrial. Horticultura Brasileira 35: 371-376. DOI http://dx.doi.org/10.1590/ S0102-053620170309