Reginaldo da Silva Romeiro

Rhizobacterial induction of systemic resistance in tomato plants: non-specific protection and increase in enzyme activities

Abstract Rhizobacteria B101R, B212R, and A068R, selected as inducers of systemic resistance against Pseudomonas syringae pv. tomato, were tested individually for biological control of multiple pathogens causing foliar diseases in tomato plants. Greenhouse bioassays were carried with five pathogens—Alternaria solani (early blight), Corynespora cassiicola (foliar blight), Oidium lycopersici (powdery mildew), Stemphilium solani (leaf spot), and Xanthomonas campestris pv. vesicatoria (bacterial spot). The level of control achieved by each rhizobacterium varied with the pathosystem studied. Isolate B101R afforded reduced disease intensity in terms of average number of leaf lesions as compared to the treatment control, protection against A. solani, S. solani, and O. lycopersici. Lipoxygenase, phenylalanine amonia-lyase, and peroxidase activities were estimated spectrophotometrically in extracts of plants grown from seeds that were microbiolized with rhizobacterium B101R, and inoculated with P. syringae pv. tomato. Increases in peroxidase and lipoxygenase activities were detected in foliar extracts from plants whose seeds had been microbiolized, while no increase in phenylalanine amonia-lyase activity was observed.

Isolation of actinomycetes and endospore-forming bacteria from the cacao pod surface and their antagonistic activity against the witches’ broom and black pod pathogens

In this study, actinomycetes and endospore-forming bacteria were isolated from the surface of cacao pods. The activity of these microorganisms againstCrinipellis perniciosa andPhytophthora palmivora, causal agents of witches’ broom and black pod diseases of cacao, respectively, was investigated. A total of 336 isolates of actinomycetes and endosporeforming bacteria were tested on a detached pod assay againstC. perniciosa. The screening procedure used proved to be fast and inexpensive, allowing the selection of five actinomycetes as the most promising isolates for the biocontrol ofC. perniciosa. Under laboratory conditions the actinomycetes were able to inhibit 100% ofC. perniciosa basidiospore germination. However, under field conditions the selected actinomycetes were unable to protect cacao pods against both pathogens. In these experiments, inhibition ofC. perniciosa ranged from 6% to 21% in relation to the control, whereas there was no inhibition of black pod caused byP. palmivora. Formulations need to be improved in order to enhance the activity of the actinomycetes against cacao pathogens in the field. Molecular identification of the selected isolates showed that they are species of the genusStreptomyces.

Bacterial spot and early blight biocontrol by epiphytic bacteria in tomato plants

(2) In memoriam Abstract - 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.

Biocontrole de doenças de parte aérea do tomateiro por Nocardioides thermolilacinus

A cultura do tomate demanda de um elevado numero de aplicacao de agrotoxicos, os quais podem ser perigosos tanto para o ambiente como para o homem. Assim, esse trabalho visa avaliar a eficacia da actinobacteria Nocardioides thermolilacinus, estirpe SON-17, como agente de biocontrole de doencas do tomateiro quando dispensado no filoplano de plantas. Inicialmente, a potencialidade foi checada in vitro contra Alternaria solani, Corynespora cassiicola, Phytophthora infestans, Pseudomonas. syringae pv. tomato, Xanthomonas campestris pv. vesicatoria. A estirpe SON-17 nao inibiu o crescimento das bacterias, mas inibiu a germinacao de esporos fungicos. No ensaio em casa de vegetacao, quando plantas de tomate foram atomizadas com suspensao de propagulos de SON-17 e quatro dias apos inoculadas com patogenos desafiantes, o antagonista foi habil em reduzir a severidade de A. solani, S. solani, C. cassiicola, X. campestris pv. vesicatoria e P. syringae pv. tomato. Em condicoes de campo, quando o actinomiceto foi dispensado semanalmente por atomizacao, a severidade da pinta preta foi reduzida em comparacao com o controle. A estirpe SON-17 deve ser melhor investigada como agente de biocontrole de doencas do tomateiro.

Métodos de isolamento de bactérias do filoplano de tomateiro visando populações específicas e implicações como agentes de biocontrole

In a process of selecting tomato (Lycopersicon esculentum) phylloplane bacteria with potential for controlling aerial diseases of this crop, different isolation methods were used to obtain the isolates from total leaf surface and also from protected sites of the phylloplane. Three hundred isolates were tested in vivo for their ability to control diseases caused by Alternaria solani, Pseudomonas syringae pv. tomato and Phytophthora infestans. The results demonstrated a predominance of antagonists in the total population originating on the surface of the leaflets harvested from the upper leaves of the plants. Only one selected antagonistic isolate obtained from the lower leaves was recovered from the protected sites of the phylloplane and/or was stress tolerant.

Evidence that the biocontrol agent Bacillus cereus synthesizes protein that can elicit increased resistance of tomato leaves to Corynespora 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.

Efficiency of phylloplane bacteria in controlling aerial tomato diseases under field conditions

The capacity of two bacteria isolated from the tomato phylloplane to control late blight (Phytophthora infestans) was investigated in the field, and compared against the effectiveness of spraying with the fungicide chlorothalonil (1.5 g a.i. L-1) or water (control). A 55% reduction in late blight intensity was observed in the leaves of the middle of the plant and 62% in those of the upper leaves when using the antagonist UFV-STB 6 (Novosphingobium capsulatum) as compared to the control. Isolate UFV-IEA 6 (Bacillus cereus) was able to reduce disease intensity by 55%, but only in the upper leaves of the tomato plants. Treatment with isolate UFV-STB 6 also led to a significant reduction in the percentage of fruits with late blight symptoms. The results demonstrate the potential of these two bacteria in controlling this disease.

Antifungal compounds as a mechanism to control Hemileia vastatrix by antagonistic bacteria

Pseudomonas putida P286 and Bacillus thuringiensis B157 controlled coffee rust under greenhouse and field conditions. Now we studied the mechanism(s) of antagonism of both bacteria to Hemileia vastatrix. Bacterial effects on urediniospore germination and disease severity were evaluated in experiments with six treatments: (i) growth broth, (ii) supernatant centrifugation, (iii) bacterial cell centrifugation and re-suspension, (iv) UV inactivation of the bacteria, (v) 523 medium, and (vi) saline solution. The treatments i to iii reduced both spore germination and disease severity. Each isolate was applied at different concentrations and time periods before inoculation of H. vastatrix. The efficiency in controlling rust was reduced at the lowest concentrations and at the largest intervals between applications. In spatial separation experiments, both bacteria did not induce systemic protection, whereas protected locally the coffee plants against H. vastatrix. Therefore, the mechanism of both isolates against H. vastatrix is attributed to the production of antifungal compound (s).

Antagonismo direto e biocontrole da podridão‑mole‑do‑tomateiro pelo uso de procariotas

O objetivo deste trabalho foi avaliar procariotas quanto ao potencial de antagonismo direto para o biocontrole da podridao-mole-do-tomateiro (Pectobacterium carotovorum subsp. carotovorum). Avaliaram-se 45 isolados bacterianos pelo teste de antibiose contra o patogeno. Foram feitos dois ensaios em que sementes de tomate (Lycopersicon esculentum Mill.) cv. Santa Clara foram infectadas com isolados antagonicos. As mudas foram transplantadas para solos infestados com suspensoes de propagulos P. carotovorum com OD540 de 0,45 e 0,65. Os antagonistas UFV-0005, UFV-043, UFV-BF112 e UFV-0006 foram eficientes em proteger plantas de tomateiro contra a podridao-mole.

Atividade de enzimas associadas ao estado de indução em mudas de cacaueiro expostas a dois actinomicetos residentes de filoplano

ABSTRACT Two antagonists selected for the biocontrol of cocoa witches’broom were investigated for their ability in triggering increases in theactivity of enzymes associated to induced resistance. In a greenhouse,thirty days old cocoa seedlings were exposed t antagonists by sprayinga propagule suspension of every antagonist or a mixture of them. Attwo, four 12 and 24 days exposing plants to the antagonists, the first Macagnan, D.; Romeiro, R.S.; Baracat-Pereira, M.C.; Lanna-Filho, R.; Batista, G.S.; Pomella, A.W.V. Activity of enzymes associa tes ofinduced resistance on cocoa seedlings exposed of two actinomycetes phylloplane residents. Summa Phytopathologica , v.34, n.1, p.34-37, 2008 RESUMO Dois antagonistas selecionados para o biocontrole da vassoura-de-bruxa do cacaueiro foram avaliados quanto a capacidade em ativarmecanismos de defesa de plantas contra patogenos. Para tanto, mudasseminais de cacaueiro “comum” foram cultivadas em casa-de-vegetacao por 30 dias e expostas aos antagonistas aplicados a mudasde cacaueiro por atomizacao, individualmente e em associacao. Oprimeiro par de folhas das mudas dos diferentes tratamentos foi