Chemical products induce resistance to Xanthomonas perforans in tomato.

The bacterial spot of tomato, caused by Xanthomonas spp., is a very important disease, especially in the hot and humid periods of the year. The chemical control of the disease has not been very effective for a number of reasons. This study aimed to evaluate, under greenhouse conditions, the efficacy of leaf-spraying chemicals (acibenzolar-S-methyl (ASM) (0.025 g.L(-1)), fluazinam (0.25 g.L(-1)), pyraclostrobin (0.08 g.L(-1)), pyraclostrobin + methiran (0.02 g.L(-1) + 2.2 g.L(-1)), copper oxychloride (1.50 g.L(-1)), mancozeb + copper oxychloride (0.88 g.L(-1) + 0.60 g.L(-1)), and oxytetracycline (0.40 g.L(-1))) on control of bacterial spot. Tomatoes Santa Clara and Gisele cultivars were pulverized 3 days before inoculation with Xanthomonas perforans. The production of enzymes associated with resistance induction (peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, ß-1,3-glucanase, and protease) was quantified from leaf samples collected 24 hours before and 24 hours after chemical spraying and at 1, 2, 4, 6, and 8 days after bacterial inoculation. All products tested controlled bacterial spot, but only ASM, pyraclostrobin, and pyraclostrobin + metiram increased the production of peroxidase in the leaves of the two tomato cultivars, and increased the production of polyphenol oxidase and ß-1,3-glucanase in the Santa Clara cultivar.

Chemical products induce resistance to Xanthomonas perforans in tomato

The bacterial spot of tomato, caused by Xanthomonas spp., is a very important disease, especially in the hot and humid periods of the year. The chemical control of the disease has not been very effective for a number of reasons. This study aimed to evaluate, under greenhouse conditions, the efficacy of leaf-spraying chemicals (acibenzolar-S-methyl (ASM) (0.025 g.L⁻¹), fluazinam (0.25 g.L⁻¹), pyraclostrobin (0.08 g.L⁻¹), pyraclostrobin + methiran (0.02 g.L⁻¹ + 2.2 g.L⁻¹), copper oxychloride (1.50 g.L⁻¹), mancozeb + copper oxychloride (0.88 g.L⁻¹ + 0.60 g.L⁻¹), and oxytetracycline (0.40 g.L⁻¹)) on control of bacterial spot. Tomatoes Santa Clara and Gisele cultivars were pulverized 3 days before inoculation with Xanthomonas perforans. The production of enzymes associated with resistance induction (peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, β-1,3-glucanase, and protease) was quantified from leaf samples collected 24 hours before and 24 hours after chemical spraying and at 1, 2, 4, 6, and 8 days after bacterial inoculation. All products tested controlled bacterial spot, but only ASM, pyraclostrobin, and pyraclostrobin + metiram increased the production of peroxidase in the leaves of the two tomato cultivars, and increased the production of polyphenol oxidase and β-1,3-glucanase in the Santa Clara cultivar.

Absence of detection of Xanthomonas axonopodis Pv. Malvacearum in cotton seeds used in the northeast region of Mato Grosso do Sul in a three-based crop season study / Ausência de detecção de Xanthomonas axonopodis Pv. Malvacearum em sementes de algodoeiro usadas na região nordeste de Mato Grosso Do Sul, em um estudo de três safras agrícolas

The aim of this work was to evaluate the presence of the causal agent of angular leaf spot, Xanthomonas axonopodis pv. malvacearum, in 38 cotton seeds samples with or without linter used in the northeast region of Mato Grosso do Sul, Brazil, during the crop seasons of 2008/09, 2009/10 e 2010/11. It was used the semi selective culture media MSSXAN (beef extract - 3 g, peptone - 5 g, soluble starch - 10 g, sucrose - 5g; Tween 80 - 10 mL; CaCl2 - 0.25 g; crystal violet solution at 1% - 150 mL; cephalexin - 50 mg; chlorothalonil - 10 mg; methyl thyophanate - 10 mg; agar ­ 15 g; sterile distilled water - 1000 ml) for the isolation of the bacteria and the suspect colonies of being X. axonopodis pv. malvacearum were purified and submitted to the Gram stain, potassium hydroxide and pathogenicity tests in the leaves of cotton plants of the susceptible genotype NC 53345. The presence of X. a. pv. malvacearum was not detected in the evaluated seed samples.

O objetivo deste trabalho foi avaliar a presença do agente causal da mancha-angular, Xanthomonas axonopodis pv. malvacearum, em 38 amostras de sementes de algodoeiro com ou sem línter utilizadas na região nordeste de Mato Grosso do Sul nas safras 2008/09, 2009/10 e 2010/11. Foi empregado o meio de cultura semi-seletivo MSSXAN (extrato de carne - 3 g; peptona - 5 g; amido solúvel - 10 g; sacarose - 5g; Tween 80 - 10 mL; CaCl2 - 0,25 g; solução de cristal violeta a 1 % - 150 µL; cefalexina - 50 mg; clorothalonil - 10 mg; tiofanato metílico - 10 mg; ágar - 15 g; água destilada esterilizada - 1.000 mL) para o isolamento da bactéria nas sementes dos diferentes lotes e colônias suspeitas de serem X. axonopodis pv. malvacearum foram purificadas e posteriormente submetidas à coloração diferencial de Gram, teste de KOH e patogenicidade em folhas de plântulas suscetíveis de algodoeiro, genótipo NC 53345. Não foi constatada a presença de X. a. pv. malvacearum nas amostras de sementes analisadas.

Fontes de resistência à murcha-de-curtobacterium em cultivares locais de feijoeiro, coletadas em Santa Catarina / Identification of resistance sources of bacterial wilt in common bean landraces, collected in Santa Catarina

Avaliou-se a reação de 73 cultivares locais de feijoeiro, coletadas em Santa Catarina, à murcha-de-curtobacterium, causada por Curtobacterium flaccumfaciens pv. flaccumfaciens. Os experimentos foram instalados em condições de casa-de-vegetação e as cultivares IAC Carioca Pyatã e IPR 88 - Uirapuru foram os padrões resistente e suscetível, respectivamente. Aos 10 dias após a emergência, houve a inoculação das plantas com o isolado FJ 36 e as avaliações dos sintomas ocorreram aos 10, 14, 21 e 28 dias após a inoculação. Foi possível identificar as cv. locais Mouro Piratuba (grupo de coloração variada) e Vagem Amarela (grupo preto) como fontes de resistência à murcha-de-curtobacterium.

It was evaluated the reaction of 73 common bean land races, collected in Santa Catarina State, to the bacterial wilt, caused by Curtobacterium flaccumfaciens pv. flaccumfaciens. The experiments were set up under greenhouse conditions and the cultivars IAC Carioca Pyatã and IPR 88 - Uirapuru were the resistant and susceptible standards, respectively. The inoculation with the strain FJ 36 was done in the 10th day after the sowing and the disease evaluations were at the 10, 14, 21 and 28th day after the inoculation. The landraces Mouro Piratuba (color bean group) and Vagem Amarela (black bean group) were identified as resistance sources of bacterial wilt of bean.

Curtobacterium flaccumfaciens pv. flaccumfaciens detection in bean seeds using a semi-selective culture medium

The bacterial wilt caused by Curtobacterium flaccumfaciens pv. flaccumfaciens is currently considered one of the most important bacterial bean disease in Brazil. One of the most effective control methods against this disease is the use of healthy seeds. However, no methods are known that could be routinely used to detect this bacterium in bean seeds under Brazilian condition. The aim of this work was to evaluate qualitative and quantitative detection methods for Curtobacterium flaccumfaciens pv. flaccumfaciens in naturally-infected bean seeds, and the detection of this pathogen in thirty bean seed samples, by sowing onto a semi-selective culture medium the leachate obtained from soaked bean seeds. Both the qualitative and quantitative methods were effective for detecting the presence of the bacteria in the seeds samples analysed. The qualitative method proved more practical for rotine use; of the thirty bean seed samples analyzed by this method, fifty percent were infected with Curtobacterium flaccumfaciens pv. flaccumfaciens.

Atualmente, a murcha-de-curtobacterium, causada por Curtobacterium flaccumfaciens pv. flaccumfaciens, é considerada uma das principais doenças baterianas da cultura do feijoeiro, no Brasil. Um dos métodos eficazes de controle desta doença é o emprego de sementes sadias. Entretanto, não se tem conhecimento de métodos que possam ser utilizados em rotina para o isolamento desta bactéria em sementes de feijoeiro. O presente trabalho teve por objetivo avaliar os métodos qualitativos e quantitativos de isolamento de Curtobacterium flaccumfaciens pv. flaccumfaciens em sementes de feijoeiro naturalmente infectadas e a detecção deste patógeno em trinta amostras de sementes de feijoeiro, pela semeadura do líquido de maceração das sementes em meio de cultura semi-seletivo. Tanto o método quantitativo quanto o quantitativo foram eficazes em detectar a presença da bactéria nas amostras de sementes analisadas. O método qualitativo mostrou-se mais prático para o uso em rotina e das trinta amostras de sementes de feijoeiro analisadas por este método cinqüenta porcento delas estavam infectadas com Curtobacterium flaccumfaciens pv. flaccumfaciens.