Deila Magna dos Santos Botelho

Intensidade da cercosporiose em mudas de cafeeiro em função de fontes e doses de silício

ABSTRACTEffect of silicon doses and sources on the intensity of the brown eye spot of coffee seedlings The objective of this work was to evaluate the effect of calcium and sodium silicate on the intensity of brown eyespot ( Cercospora coffeicola ) in coffee ( Coffea arabica ) seedlings (Catuai IAC 99) by using doses (0; 0.32; 0.63 and 1.26g of SiO 2 .kg -1 ) of substrate. Five evaluations were done by counting the number of diseased plants, number of leaves withlesions, number of lesions per leaf and total number of lesions per plant. The concentration of macro, micronutrients,silicon and lignin in the leaves was determined at the end of the experiment. The lowest area under the disease progresscurve of the total number of lesions was observed with 0.84 g.kg -1 of sodium silicate. Diseased plants were found to havea linear decrease of area under the disease progress curve and an increase in the concentration of lignin up to the dose of0.52 g.kg -1 of sodium silicate. The increase of sodium silicate and dose application into the soil up to 0.53 g.kg decreasedthe concentration of SiO

Evaluation of antifungal activity of essential oils against potentially mycotoxigenic Aspergillus flavus and Aspergillus parasiticus

The antifungal activity of essential oils of fennel (Foeniculum vulgare Mill., Apiaceae), ginger (Zingiber officinale Roscoe, Zingiberaceae), mint (Mentha piperita L., Lamiaceae) and thyme (Thymus vulgaris L., Lamiaceae) was evaluated against mycotoxin producers Aspergillus flavus and A. parasiticus. High Resolution Gas Chromatography was applied to analyze chemical constituents of essential oils. The effect of different concentrations of essential oils was determined by solid medium diffusion assay. Mycelial growth and sporulation were determined for each essential oil at the concentrations established by solid medium diffusion assay. At the fifth, seventh and ninth days the mycelial diameter (O mm) and spore production were also determined. FUN-1 staining was performed to assess cell viability after broth macrodilution assay. Trans-anethole, zingiberene, menthol and thymol are the major component of essential oils of fennel, ginger, mint and thyme, respectively. The effective concentrations for fennel, ginger, mint and thyme were 50, 80, 50 and 50% (oil/DMSO; v/v), respectively. The four essential oils analysed in this study showed antifungal effect. Additionally, FUN-1 staining showed to be a suitable method to evaluate cell viability of potential mycotoxigenic fungi A. flavus and A. parasiticus after treatment with essential oils.

Silicon in plant disease control

All essential nutrients can affect the incidence and severity of plant diseases. Although silicon (Si) is not considered as an essential nutrient for plants, it stands out for its potential to decrease disease intensity in many crops. The mechanism of Si action in plant resistance is still unclear. Si deposition in plant cell walls raised the hypothesis of a possible physical barrier to pathogen penetration. However, the increased activity of phenolic compounds, polyphenol oxidases and peroxidases in plants treated with Si demonstrates the involvement of this element in the induction of plant defense responses. The studies examined in this review address the role of Si in disease control and the possible mechanisms involved in the mode of Si action in disease resistance in plants.

Atividade antifúngica, in vitro, do óleo de café verde

The objective of this study was to evaluate the effect of direct contact and volatile fraction of from green coffee oil, tested at concentrations of 500, 1,000, 1,500 and 2,000 µL L-1, on mycelial growth and sporulation of Penicillium roqueforti and Rhizopus stolonifer . The essential oil of clove at a concentration of 800 µL L-1 was used for comparison. At concentrations of 1,500 and 2,000 µL L-1, the green coffee oil in direct contact caused a reduction of sporulation for R. stolonifer, similar to clove oil. In the volatile fraction of the green coffee oil, there was a significant reduction in sporulation of P. roqueforti and R. stolonifer at a concentration of 2,000 µL L-1. The green coffee oil, in direct contact or by volatilization, significantly reduced the mycelial growth and sporulation of both fungi compared to the control.

Cercosporiosis resistance in coffee germplasm collection

Cercosporiosis, or brown eye spot, is currently one of the main diseases of the coffee tree. It is caused by Cercospora coffeicola Berk. & Cooke. Nevertheless, genetic resistance to this disease has not yet been explored in any depth. Our objectives (a) were evaluate the response of 124 accessions from the germplasm collection of the Minas Gerais State (GC), Brazil, and eight commercial cultivars of C. arabica to cercosporiosis and (b) determine the best way to perform early progenies selections via controlled greenhouse experiments. Three controlled greenhouse experiments (1–3) were run in different seasons to determine the best way to proceed the selection. The seedlings were inoculated with a four isolates mixture obtained from different regions. The experimental data were analyzed individually (1–3), in a joint analysis, and as repetitions of a randomized complete block design. In each analysis we estimated genetic parameters and E-BLUP (empirical best linear unbiased predictor) genotypic values of the access. There was genetic variability to C. coffeicola resistance among the coffee tree accessions germplasm collection. Therefore, genetic improvements could be obtained by selection. Experimental repetitions in different seasons increase the selection efficiency and reliability of resistant genotypes with low cercosporiosis severity. The genotype Sarchimor MG 8840 showed the highest resistance level followed by Guatenano and the Timor Hybrid UFV 377-34, Timor Hybrid UFV 376-14 BE 5, and Wush–Wush × Timor Hybrid UFV 366-08.

Imobilização de fungos filamentosos com potencial para uso agroindustrial

A imobilizacao celular representa uma alternativa para a conducao de bioprocessos. As celulas ficam retidas em matrizes e podem ser utilizadas por longos periodos. O objetivo deste trabalho foi testar uma nova metodologia de imobilizacao de fungos com custo reduzido, avaliar a viabilidade e seguranca dos fungos submetidos ao novo metodo de encapsulamento e determinar a temperatura ideal para armazenar os fungos imobilizados. Os micelios dos fungos Aspergillus niger, Cladosporium cladosporioidese Penicillium solitum foram misturados com 15 g de arroz triturado e 3 g de alginato de sodio, que gotejava em uma solucao de cloreto de calcio a 0,25 M para a formacao dos grânulos. Apos a secagem em estufa a 26oC, os grânulos foram armazenados em temperaturas ambiente, geladeira e freezer. Os plaqueamentos foram realizados a cada 15 dias em meio de cultura. As avaliacoes do tamanho das colonias e esporulacao foram realizadas 7, 14 e 21 dias apos o plaqueamento, durante 195 dias para A. niger, 225 dias para C. cladosporioides e 210 dias para P. solitum. A temperatura de armazenamento nao afetou o desenvolvimento micelial de A. nigere P. solitum. Porem, a esporulacao foi reduzida para os grânulos armazenados no freezer. O desenvolvimento micelial de C. cladosporioides foi influenciado pela temperatura. Os grânulos conservados em temperatura ambiente tiveram menor viabilidade. Na analise de microscopia eletronica de varredura, observou-se que a imobilizacao e um metodo seguro no qual o micelio fungico permanece no interior do grânulo, facilitando o transporte, o armazenamento e a aplicacao de micro-organismos.