Fabiano José Perina

Potential of essential oils for the control of brown eye spot in coffee plants

Este trabalho avaliou o efeito in vitro de oleos essenciais extraidos de canela, citronela, capim-limao, cravo-da-india, arvore-de-cha, tomilho, nim e eucalipto na germinacao de conidios e no crescimento micelial de Cercospora coffeicola, a eficacia destes oleos no controle da cercosporiose-do-cafeeiro em mudas das cultivares Catucai 2SL, Catuai IAC 62 e Mundo Novo 379/19 em casa de vegetacao; e seus efeitos sobre os eventos iniciais de germinacao e infeccao do patogeno in vivo por meio de microscopia eletronica de varredura. Todos os oleos essenciais inibiram a germinacao dos conidios com o aumento das concentracoes. Os oleos de cravo-da-india, canela, nim, tomilho e capim-limao inibiram o crescimento micelial de C. coffeicola. Os oleos de canela e citronela foram os mais promissores no controle da cercosporiose em todas as cultivares. Em microscopia eletronica de varredura, os oleos de canela e citronela reduziram a germinacao e o desenvolvimento micelial in vivo de C. coffeicola oito e 16 horas apos a inoculacao, promovendo, em alguns casos, o extravasamento do conteudo celular. Oleos essenciais de canela e citronela reduziram a incidencia e a severidade da cercosporiose, alem de apresentar efeito toxico direto ao patogeno.

Antibacterial activity of essential oils on Xanthomonas vesicatoria and control of bacterial spot in tomato

The objective of this work was to evaluate the effects of plant essential oils (EOs) on the growth of Xanthomonas vesicatoria, on bacterial morphology and ultrastructure, and on the severity of tomato bacterial spot. EOs from citronella, clove, cinnamon, lemongrass, eucalyptus, thyme, and tea tree were evaluated in vitro at concentrations of 0.1, 1.0, 10, and 100% in 1.0% powdered milk. The effect of EOs, at 0.1%, on the severity of tomato bacterial spot was evaluated in tomato seedlings under greenhouse conditions. The effects of citronella, lemongrass, clove, and tea tree EOs, at 0.1%, on X. vesicatoria cells were evaluated by transmission electron microscopy. All EOs showed direct toxic effect on the bacteria at a 10%-concentration in vitro. Under greenhouse conditions, the EOs of clove, citronella, tea tree, and lemongrass reduced disease severity. EOs of clove and tea tree, and streptomycin sulfate promoted loss of electron-dense material and alterations in the cytoplasm, whereas EO of tea tree promoted cytoplasm vacuolation, and those of citronella, lemongrass, clove, and tea tree caused damage to the bacterial cell wall. The EOs at a concentration of 0.1% reduce the severity of the disease. Resumo - O objetivo deste trabalho foi avaliar o efeito de oleos essenciais (OEs) no crescimento de Xanthomonas vesicatoria, na morfologia e na ultraestrutura bacteriana, e na severidade da mancha-bacteriana do tomateiro. OEs de citronela, cravo-da-india, canela, capim-limao, eucalipto, tomilho e arvore-de-cha foram avaliados in vitro nas concentracoes de 0,1, 1,0, 10 e 100% em leite em po a 1,0%. O efeito dos OEs, a 0,1%, na severidade da mancha-bacteriana do tomateiro foram avaliados em plantas de tomateiro em casa de vegetacao. Os efeitos dos oleos de citronela, capim-limao, cravo-da-india e arvore-de-cha, a 0,1%, nas celulas de X. vesicatoria foram avaliados por meio de microscopia eletronica de transmissao. Todos os OEs apresentaram efeito toxico direto sobre as bacterias na concentracao de 10% in vitro. Em casa de vegetacao, os OEs de cravo-da-india, citronela, arvore-de-cha e capim-limao reduziram a severidade da doenca. Os OEs de cravo-da-india e arvore-de-cha, e o sulfato de estreptomicina promoveram perda de material eletro-denso e alteracoes no citoplasma, enquanto o OE de arvore-de-cha promoveu vacuolizacao do citoplasma, e os de citronela, capim-limao, cravo-da-india e arvore-de-cha causaram danos a parede celular bacteriana. Os OEs, na concentracao de 0,1%, reduzem a severidade da doenca. Termos para indexacao: controle alternativo de doencas de plantas, ultraestrutura celular, bacteria fitopatogenica.

Essential oils for rust control on coffee plants

A ferrugem e considerada a doenca de maior importância no cafeeiro, pois causa acentuada desfolha nas plantas e, consequentemente, reducao na produtividade. Este trabalho avaliou o efeito in vitro de oleos essenciais de canela, citronela, capim-limao, cravo-da-india, arvore-de-cha, tomilho, nim e eucalipto na germinacao de urediniosporos de Hemileia vastatrix; a eficacia desses oleos no controle da ferrugem em mudas de cafeeiro das cultivares Catucai 2SL, Catuai IAC 62 e Mundo Novo 379/19 em casa de vegetacao; e o efeito dos oleos mais promissores sobre urediniosporos de H. vastatrix por meio de microscopia eletronica de transmissao (MET). Todos os oleos essenciais inibiram a germinacao dos urediniosporos com o aumento das concentracoes. Todos os oleos promoveram controle parcial da doenca em casa de vegetacao. No entanto, os oleos de tomilho, cravo-da-india e citronela, na dose de 1000 µL L-1, foram os mais eficazes no controle da doenca nas cultivares Catucai 2SL, Catuai IAC 62 e Mundo Novo 379/19, respectivamente. Nas imagens geradas em MET, observou-se que urediniosporos expostos aos oleos de cravo-da-india, citronela e tomilho apresentaram desorganizacao citoplasmatica e vacuolizacao celular, sendo esta mais pronunciada em urediniosporos expostos ao oleo de citronela. Os oleos de tomilho, cravo-da-india e citronela sao promissores no controle da ferrugem em cafeeiro.

Anadenanthera colubrina (Vell.) Brenan produces steroidal substances that are active against Alternaria alternata (Fr.) Keissler and that may bind to oxysterol‐binding proteins

BACKGROUND In previous studies, the extract from Anadenanthera colubrina was active against Alternaria alternata in vitro and reduced the disease caused by this fungus on Murcott tangor fruits to levels that have been obtained using commercial fungicides. Therefore, the goal of the present work was to isolate and identify the active substances in this extract and identify in silico their protein target in the fungus. RESULTS The bioguided fractionation of the methanol extract from the fruits of A. colubrina resulted in the isolation of β-sitosterol and β-sitosteryl linoleate, which had minimal inhibitory concentrations (MICs) of 250 and 500 µg mL(-1) , respectively, against A. alternata. Under the same conditions, the MICs for two commercial fungicides were 1250 and 19 µg mL(-1) . In silico studies showed that these steroidal substances bind well to oxysterol-binding proteins from Saccharomyces cerevisiae. CONCLUSION β-Sitosterol and β-sitosteryl linoleate, produced by A. colubrina, are active against A. alternata. In silico studies suggest that these substances may act by binding to oxysterol-binding proteins. Therefore, both substances and these proteins have potential use in the development of new steroidal structures and analogues to control the disease caused by A. alternata.

Essential oils on the control of stem and ear rot in maize

Stem and ear rot caused by Stenocarpella maydis are responsible for severe losses in maize production. Treatment of seeds with fungicides may induce environmental damage. Hence, this study aimed to evaluate the effects of essential oils extracted from Cymbopogon winterianus, Thymus vulgaris, Cymbopogon citratus, Corymbia citriodora, Cinnamomum zeylanicum, and Syzygium aromaticum on the development of in vitro S. maydis. In addition, maize seeds were treated with these essential oils to determine their possible mode of action and effects. The oils from S. aromaticum, C. zeylanicum, and T. vulgaris inhibited fungal development at concentrations higher than 0.025%. The oils from S. aromaticum and C. zeylanicum showed seed germination rates of 89.0% and 84.5%, which were higher than that of the control. The oils from S. aromaticum and C. zeylanicum reduced the pathogen incidence in the seeds to 39.0% and 28.0%, respectively. Further, these oils as well as that from T. vulgaris produced lower reduction of maize stand. Scanning electron microscopy examination revealed that essential oils from S. aromaticum and T. vulgaris acted directly on the conidia, impeding germination. The findings suggest that the oils from S. aromaticum, C. zeylanicum, and T. vulgaris are potential alternatives for maize seed treatment in the control of S. maydis.

Citronella essential oil in the control and activation of coffee plants defense response against rust and brown eye spot

The rust and brown eye spot are the main coffee diseases. The losses are due to intense defoliation of plants, which has reduced its production and longevity. The brown eye spot also occurs in fruits, with negative effects on the beverage quality. Some essential oils have presented promising results in the control of plant diseases, as an alternative to the use of fungicides. The objective of this study was to evaluate citronella essential oil in the control of rust and brown eye spot and in the activation of coffee plants defense responses. Twelve-month-old plants were sprayed with citronella oil 1000 µL L-1, acibenzolar-S-methyl 200 mg L-1 and tebuconazole fungicide 200 mg L-1. Plants were inoculated with Hemileia vastatrix and Cercospora coffeicola seven days later. The application was repeated after 30 days. Plants with five months were sprayed with the same treatments to assess the induced defense responses. Citronella oil controlled rust and brown eye spot with efficiencies of 47.2% and 29.7%, respectively, while tebuconazole presented control of 96.5% and 90.5%, respectively. Acibenzolar-S-methyl reduced brown eye spot by 55.9% and showed no significant control of rust. Citronella oil increased peroxidase and chitinase activities in five months coffee plants 336, and 24 and 336 hours after spraying, respectively. Acibenzolar-S-methyl increased peroxidase, chitinase and ββ-1,3-glucanase activities 192, 288 and 336; 24 and; 240 hours after spraying, respectively. The treatments did not increase accumulation of phenols, but a significant increase in lignin was observed in plants sprayed with citronella oil.

Essential oils and whole milk in the control of soybean powdery mildew

This research aimed to evaluate the potential of essential oils (EOs) and cows whole milk (CWM) in order to control soybean powdery mildew and to estimate the most effective concentrations of these natural products in reducing the disease severity on soybean plants. Three experiments were carried out: The first experiment evaluated and selected the most effective treatments to reduce the severity of soybean powdery mildew under greenhouse conditions; the second experiment evaluated the effect of CWM and EOs of citronella, lemongrass, eucalyptus, cinnamon and tea tree on the pathogen through the ultrastructure analysis of soybean leaflets infected by Erysiphe diffusa using the scanning electron microscope (SEM) and light microscope (LM) technology. In the third experiment, the most effective products were tested at several concentrations in order to define the most effective concentrations to reduce disease severity under greenhouse conditions. The treatments CWM (100mL L-1) and EOs of citronella, lemongrass and eucalyptus (1.0mL L-1), reduced the disease severity from 67 to 74%. Direct effects from all natural products tested on the structures of E. diffusa were demonstrated through the SEM and LM analysis. Concentrations at 1.5mL L-1 for EOs of citronella, lemongrass and eucalyptus and also at 180mL L-1 for the treatment CWM were the most effective against E. diffusa on soybean.

Anatomia foliar de microtomateiros fitocromo-mutantes e ultra-estrutura de cloroplastos

Plantas fitocromo-mutantes tem sido utilizadas com o intuito de caracterizar isoladamente, dentre os demais fotorreceptores, a acao dos fitocromos sobre eventos ligados a fotomorfogenese. Raros sao os estudos que relatam a acao dos fitocromos sobre aspectos estruturais, embora sejam fundamentais a compreensao do desenvolvimento das plantas. Neste trabalho, objetivou-se analisar caracteristicas ultraestruturais de cloroplastos e aspectos anatomicos foliares dos microtomateiros (Solanum lycopersicum L. cv. Micro-Tom) fitocromo-mutantes aurea (subexpressa fitocromos), hp1 e atroviolacea (ambos supra-responsivos a eventos mediados por fitocromo) em plantas em estagio de floracao. Observou-se que os fitocromos sao responsaveis pela expressao de muitas caracteristicas anatomicas da epiderme foliar, assim como do mesofilo e da ultraestrutura dos cloroplastos.