Pulverização foliar com agentes bacterianos de biocontrole para controle do crestamento bacteriano comum do feijoeiro

The objective of this work was to evaluate the effect of foliar spraying with bacterial biocontrol agents (BBAs) on the control of common bacterial blight (CBB) of bean, and on the induction of systemic resistance in bean plants. CBB control by BBAs was evaluated by spraying bean leaves 48 and 24 hours before and after pathogen inoculation (BPI and API, respectively), with: DFs93, Bacillus cereus; DFs513, Pseudomonas veronii; DFs769, B. cereus; the C01 combination, DFs93 + DFs769 + DFs831 (Pseudomonas fluorescens); the C03 combination, DFs348 (Bacillus sp.) + DFs769 + DFs831; and water (control). Systemic effects were analyzed after spraying DFs513, DFs769, C03, and water 72 and 48 hours BPI. Phaseolin production induced by DFs348, DFs513, DFs769, DFs831, and water was also assessed. DFs513, DFs769, and C03 significantly reduced disease incidence (area under disease progress curve), regardless of spraying time and disease severity when sprayed 72 and 48 hours BPI. The DFs769 and DFs831 isolates induced the accumulation of phytoalexin (phaseolin). Therefore, DFs513, DFs769, and C03 show potential for the biocontrol of CBB when applied preventively on bean leaves, besides inducing systemic resistance.O objetivo deste trabalho foi avaliar o efeito da pulverização foliar de agentes bacterianos de biocontrole (ABB) no controle do crestamento bacteriano comum do feijoeiro (CBC) e na indução de resistência sistêmica em plantas de feijão. O controle do CBC por ABB foi avaliado por meio da pulverização, em folhas de feijoeiro, 48 e 24 horas antes e depois da inoculação do patógeno (AIP e DIP, respectivamente), de: DFs93, Bacillus cereus; DFs513, Pseudomonas veronii; DFs769, B. cereus; combinação C01, DFs93 + DFs769 + DFs831 (Pseudomonas fluorescens); combinação C03, DFs348 (Bacillus sp.) + DFs769 + DFs831; e água destilada (testemunha). Os efeitos sistêmicos foram analisados após pulverização de DFs513, DFs769, C03 e água 48 e 72 horas AIP. Também foi avaliada a produção de faseolina induzida por DFs348, DFs513, DFs769, DFs831 e água. DFs513, DFs769 e C03 reduziram significativamente a incidência da doença (área abaixo da curva de progresso da doença), independentemente do momento da aplicação e da severidade da doença quando pulverizados 48 e 72 horas AIP. Os isolados DFs769 e DFs831 induziram o acúmulo de fitoalexina (faseolina). Portanto, DFs513, DFs769 e C03 apresentam potencial para o biocontrole do CBC quando pulverizados preventivamente em folhas de feijão, além de atuarem como indutores de resistência

Biocontrol of sheath blight and root‑knot nematode and growth promotion of rice plants by rhizobacteria

O objetivo deste trabalho foi avaliar a compatibilidade entre rizobactérias biocontroladoras pré-selecionadas e o efeito de suas combinações sobre a queima-das-bainhas (Rhizoctonia solani), a meloidoginose (Meloidogyne graminicola) e a promoção de crescimento de plantas de arroz. A compatibilidade foi determinada pela antibiose. O efeito das combinações de isolados foi avaliado por microbiolização de sementes de arroz, cultivar El Paso L144, com suspensões das rizobactérias DFs185 (Pseudomonas synxantha), DFs223 (P. fluorescens), DFs306 (ainda não identificada), DFs416 e DFs418 (Bacillus sp.). Essas rizobactérias foram usadas isoladamente ou combinadas em arranjos de dois, três e quatro isolados. O isolado DFs223 não foi combinado com nenhum outro por ser incompatível com os demais isolados. Cinco combinações de rizobactérias (DFs185/418, DFs306/416, DFs306/418, DFs416/418, DFs185/306/418) e o isolado DFs306 destacaram-se por reduzir a reprodução de M. graminicola e promover o crescimento das plantas. A combinação DFs185/306 apresentou os melhores resultados quanto ao controle de R. solani e à promoção de crescimento. Acombinação DFs306/416 proporcionou os melhores resultados para o controle das duas doenças.The objective of this work was to evaluate the compatibility between previously selected biocontroller rhizobacteria and the effect of their combination upon sheath blight (Rhizoctonia solani), root-knot nematode (Meloidogyne graminicola) and growth promotion in rice plants. The compatibility between these bacteria was determined by the overlay antibiosis. The effect of isolate combinations was evaluated by seed microbiolization of the rice cultivar El Paso L144 with rhizobacteria suspensions of DFs185 (Pseudomonas synxantha), DFs223 (P. fluorescens), DFs306 (unidentified), DFs416 and DFs418 (Bacillus sp.). These rhizobacteria were used alone or combined in arrangements of two, three and four isolates. The DFs223 isolate was not combined because it is incompatible with the other bacteria. Five rhizobacteria combinations (DFs185/418, DFs306/416, DFs306/418, DFs416/418, DFs185/306/418) and the isolate DFs306 stood out for reducing M. graminicola reproduction and promoting plant growth. Combination DFs185/306 presented the best results for the control of R. solani and for growth promotion. The DFs306/416 combination provided the best results for the control of the two diseases

Potencial de rizobactérias no controle de Meloidogyne incognita em figueira

A figueira é economicamente importante pelo papel social que representa no contexto da agricultura familiar. No entanto, sua viabilidade econômica pode ser comprometida em áreas infestadas pelo nematoide das galhas (Meloidogyne incognita) devido à carência de medidas de controle efetivas e disponíveis. Assim, a inserção do controle biológico no manejo integrado dessa praga constitui-se como uma estratégia importante. As rizobactérias são consideradas biocontroladoras promissoras por promover o crescimento vegetal e/ou inibir a ação parasítica dos fitonematoides sobre as plantas hospedeiras. Dessa forma, objetivou-se com esse trabalho, avaliar o desempenho de 14 isolados bacterianos provenientes da rizosfera de figueira e de rochas de folhelhos betuminosos, no biocontrole de M. incognita em figueira. Mudas de figueira cv. ‘Roxo de Valinhos' microbiolizadas com os isolados bacterianos foram transplantadas em solo naturalmente infestado com M. incognita. Sete isolados (F08, F25, F71, F76, F78, FB34 e FB59), reduziram significativamente o fator de reprodução do nematoide das galhas (P<0,05) em valores que variaram entre 20 e 49%. Contudo, além de suprimir a multiplicação do patógeno, o isolado F78 (Streptomyces sp.) promoveu aumento do peso de raízes, maiores índices de clorofila e conteúdo das enzimas de resistência peroxidades e polifenol-oxidades, e, redução na concentração de fenóis das figueiras microbiolizadas. Nesse sentido, a condução de trabalhos adicionais nesse patossistema pode possibilitar a melhor compreensão dos mecanismos de atuação das bactérias testadas no biocontrole de M. incognita, além de fornecer informações adicionais para a implementação dessa técnica em um programa de manejo integrado do nematoide das galhas.The fig tree is economically important for the social role it plays in the context of family farming. However, its economic viability can be compromised in infested areas by root-knot nematode (Meloidogyne incognita) due to lack of effective and available control measures. Therefore, the insertion of the biological control on the integrated management of this pest constitutes an important strategy. The rhizobacteria are considered promising biocontrol agents for promoting plant growth and or inhibit the parasitic action of plant-parasitic nematodes in the host plants. So, the aim of this study was to evaluate the performance of 14 bacterial isolates from the rhizosphere of fig and shale rocks in biocontrol of M. incognita in fig. Seedlings of fig plants of cv. 'Roxo de Valinhos' were microbiolized with these bacterial isolates and they were transplanted in soil naturally infested with M. incognita subsequently. Seven isolates (F08, F25, F71, F76, F78, FB34 and FB59) reduced the reproduction factor of the root-knot nematode (P <0.05) at rate ranging between 20 and 49%. Besides to suppress the pathogen reproduction, the isolated F78 (Streptomyces sp.) promoting increasing of root weight, higher chlorophyll contents and content peroxidases and polyphenol oxidases resistance enzymes, and reduction of the phenol concentration of microbiolized fig plants. In this sense, conducting further studies in this pathosystem can enable a better understanding of the action mechanisms of the bacteria tested in the biocontrol of M. incognita, as well as providing additional information for the implementation of this technique in an integrated management program of root-knot nematode

Spectrum of biocontrol bacteria to control leaf, root and vascular diseases of dry bean

AbstractBacterial biocontrol agents, previously selected to control bacterial blight and anthracnose, were evaluated for the control of bacterial wilt, fusarium wilt, charcoal rot and angular leaf spot of dry beans. The seeds were microbiolized with these bacteria singly or in combinations. The microbiolization resulted in reduction of severity of all four diseases, showing wide spectrum of diseases control by these bacteria. However, the severity reduction of all four diseases by combination C01 composed of isolates DFs093 and DFs769 of Bacillus cereus and DFs831 of Pseudomonas fluorescens was significantly higher than if the seeds were microbiolized by a single isolate of a biocontrol agent

AFLP analysis of Xanthomonas axonopodis and X. arboricola strains used in xanthan production studies reveal high levels of polymorphism

Amplified fragment length polymorphism (AFLP) was used to analyze the genetic diversity of 14 strains of Xanthomonas arboricola pv. pruni and seven strains of X. axonopodis pv. phaseoli, which are used in xanthan production studies. Relationships identified by the AFLP profiles were assessed for xanthan production capacity, geographical location and host plant. Strains were isolated from 10 different geographic regions in South and Southeast States in Brazil. Data were analyzed for genetic similarity using the Dice coefficient and subjected to UPGMA cluster analysis. A total of 128 AFLP fragments were generated from four primer combinations: EcoRI+C/MseI+0, EcoRI+A/MseI+0, EcoRI+G/MseI+T and EcoRI+G/MseI+A. Of these, 96.1% were polymorphic. X. axonopodis pv. phaseoli (S D = 0.27) was shown to be more polymorphic than X. arboricola pv. pruni (S D = 0.58). All 14 pathovar pruni strains were included in a single main group (S D = 0.58), while the pathovar phaseoli strains were divided into three separate groups, with one group containing five strains (S D = 0.38) and two isolated groups (S D = 0.31 and 0.27) composed of only one strain each. Species were distinguished by three and eight specific AFLP markers present in the pathovar phaseoli and the pathovar pruni, respectively. For the unique strain without xanthan production capacity (X. axonopodis pv. phaseoli str. 48), nine specific AFLP bands were found. There was no evidence that geographic area or host plant influenced genetic heterogeneity. Correlations between AFLP patterns and xanthan production capacity were found in some strains, but were not consistent enough to establish a relationship

Potencial de rizobactérias no controle de Meloidogyne incognita em figueira

The fig tree is economically important for the social role it plays in the context of family farming. However, its economic viability can be compromised in infested areas by root-knot nematode (Meloidogyne incognita) due to lack of effective and available control measures. Therefore, the insertion of the biological control on the integrated management of this pest constitutes an important strategy. The rhizobacteria are considered promising biocontrol agents for promoting plant growth and or inhibit the parasitic action of plant-parasitic nematodes in the host plants. So, the aim of this study was to evaluate the performance of 14 bacterial isolates from the rhizosphere of fig and shale rocks in biocontrol of M. incognita in fig. Seedlings of fig plants of cv. 'Roxo de Valinhos' were microbiolized with these bacterial isolates and they were transplanted in soil naturally infested with M. incognita subsequently. Seven isolates (F08, F25, F71, F76, F78, FB34 and FB59) reduced the reproduction factor of the root-knot nematode (P <0.05) at rate ranging between 20 and 49%. Besides to suppress the pathogen reproduction, the isolated F78 (Streptomyces sp.) promoting increasing of root weight, higher chlorophyll contents and content peroxidases and polyphenol oxidases resistance enzymes, and reduction of the phenol concentration of microbiolized fig plants. In this sense, conducting further studies in this pathosystem can enable a better understanding of the action mechanisms of the bacteria tested in the biocontrol of M. incognita, as well as providing additional information for the implementation of this technique in an integrated management program of root-knot nematode.A figueira é economicamente importante pelo papel social que representa no contexto da agricultura familiar. No entanto, sua viabilidade econômica pode ser comprometida em áreas infestadas pelo nematoide das galhas (Meloidogyne incognita) devido à carência de medidas de controle efetivas e disponíveis. Assim, a inserção do controle biológico no manejo integrado dessa praga constitui-se como uma estratégia importante. As rizobactérias são consideradas biocontroladoras promissoras por promover o crescimento vegetal e/ou inibir a ação parasítica dos fitonematoides sobre as plantas hospedeiras. Dessa forma, objetivou-se com esse trabalho, avaliar o desempenho de 14 isolados bacterianos provenientes da rizosfera de figueira e de rochas de folhelhos betuminosos, no biocontrole de M. incognita em figueira. Mudas de figueira cv. ‘Roxo de Valinhos' microbiolizadas com os isolados bacterianos foram transplantadas em solo naturalmente infestado com M. incognita. Sete isolados (F08, F25, F71, F76, F78, FB34 e FB59), reduziram significativamente o fator de reprodução do nematoide das galhas (P<0,05) em valores que variaram entre 20 e 49%. Contudo, além de suprimir a multiplicação do patógeno, o isolado F78 (Streptomyces sp.) promoveu aumento do peso de raízes, maiores índices de clorofila e conteúdo das enzimas de resistência peroxidades e polifenol-oxidades, e, redução na concentração de fenóis das figueiras microbiolizadas. Nesse sentido, a condução de trabalhos adicionais nesse patossistema pode possibilitar a melhor compreensão dos mecanismos de atuação das bactérias testadas no biocontrole de M. incognita, além de fornecer informações adicionais para a implementação dessa técnica em um programa de manejo integrado do nematoide das galhas

Biocontrol and seed transmission of Bipolaris oryzae and Gerlachia oryzae to rice seedlings

Bipolaris oryzae and Gerlachia oryzae, which cause rice brown spot and leaf scald, respectively, are mainly disseminated by seeds. The aim of this study was to evaluate the potential of seeds microbiolization to reduce transmission of these pathogens to seedlings by using the bacteria DFs185 (Pseudomonas synxantha), DFs223 (P. fluorescens), DFs306 (unidentified) and DFs418 (Bacillus sp.). Seeds naturally infested/infected with both pathogens were immersed in suspension of these bacteria (A540 = 0.5) individually or in saline solution (control treatment). After 30 minutes of agitation at 10 ºC, 400 seeds were submitted to a sanity test through the blotter method and the isolate DFs223 was the best to reduce the incidence of B. oryzae and G. oryzae in both seed lots evaluated. Seeds treated like above were sowed in sterilized vermiculite. Seed transmission and growth promotion were recorded after 21 days of incubation in the same conditions. The isolates DFs185 and DFs306 reduced transmission of both pathogens, although the isolate DFs306 was the one wich gave the greatest growth increases. The evaluation of the in vitro antibiosis showed that isolates inhibited the mycelial growth of both pathogens, except DFs306. It is possible to affirm that these bacteria have the potential to be used as a seed treatment for seed-borne disease control