Adélia Aziz Alexandre Pozza

Influência da nutrição mineral na intensidade da mancha-de-olho-pardo em mudas de cafeeiro

The experiment was carried out at the coffee nursery of the Universide Federal de Vicosa, in Vicosa, MG, Brazil, using nutrient circulating solution to evaluate the intensity of brown-eye spot (Cercospora coffeicola), variety Catuai Vermelho, as a function of N and K. Acompletely randomized design with 16 treatments, three replicates, and two plants per plot was used in a factorial with four levels of K (3, 5, 7 and 9mmol/L) combined with four levels of N (3, 7, 11 and 15mmol/L). After seven inoculations and evaluations, the plants were picked. Total dry matter production, total leaf area, and the area below the curve of progress (AACP) for the total number of leaves were not influenced by the levels of K, but increased with increasing levels of N. There was increase in AACP areas for the number of lesions per leaf and defoliation, with the increase of K levels, and a reduction of N levels. The increase in K levels reduced the Ca and Cu leaf contents, indicating possible relation between its contents and the increase of the disease. The P, Mg, Mn, and Fe leaf contents were not influenced by the K levels, and had a small reduction with increased N contents in the nutrient solution, increasing thereafter.

Efeito do silício no controle da cercosporiose em três variedades de cafeeiro

A cercosporiose do cafeeiro (Coffea arabica), causada por Cercospora coffeicola, e uma das mais importantes doencas na fase de viveiro. O objetivo desse trabalho foi avaliar o efeito da aplicacao de silicio (1 g de CaSiO3 incorporada em 1 kg do substrato utilizado para encher os tubetes) no controle dessa doenca em tres variedades de cafeeiro (catuai, mundo novo e icatu) e, determinar quais os possiveis fatores de resistencia associados. As plantas com dois pares de folhas foram inoculadas com suspensao de 1,4 x 104 conidios de C. coffeicola por ml. Aos sete meses apos a inoculacao avaliaram-se a porcentagem de folhas lesionadas e o numero total de lesoes por planta. Apos essa avaliacao, retiraram-se amostras das folhas para o estudo em Microscopia Eletronica de Varredura (MEV) e Microanalise de Raios-X (MAX). As plantas da variedade catuai tratadas com silicato, tiveram reducao de 63,2% nas folhas lesionadas e de 43% no total de lesoes por planta, em relacao a testemunha. A MAX e o mapeamento para Si indicaram distribuicao uniforme do elemento em toda a superficie abaxial das folhas de cafeeiro nas tres variedades tratadas. Nas folhas das plantas nao tratadas, o Si foi raramente encontrado. Nas imagens de MEV tambem foi observada camada de cera bem desenvolvida na superficie inferior das folhas originarias de todas as plantas tratadas, sendo esta mais espessa em catuai e rara ou ausente nas nao tratadas.

Incidência e severidade da cercosporiose do cafeeiro em função do suprimento de potássio e cálcio em solução nutritiva

An experiment was carried out at UFLA to evaluate the incidence and severity of the brown eye spot caused by Cercospora coffeicola in coffee (Coffea arabica) seedlings, in relation to different dosages of K and Ca in nutrient solution. The experimental design was completely randomized with 16 treatments, three replicates and two plants per replicate. Treatments were displayed in a 4 x 4 factorial scheme, with four levels of K (1, 3, 5 and 7 mmol/l) and four levels of Ca (2, 4, 6 and 8 mmol/l). The seedlings were inoculated, every week, for three months, with a conidial suspension of C. coffeicola of 15,000 conidia/ml. Total leaf area, total number of leaves and total injury number were obtained from seven evaluations made every fortnight. After the final evaluations, coffee seedlings were collected, the injured leaf area and the dry matter weight determined. The K x Ca interaction influenced total injury, total number of leaves and percentage of injured leaf area under the disease progress curve. The dosages of K reduced the total dry matter, the total leaf area and the area under the disease incidence progress curve, while the dosages of Ca influenced the total leaf area and the area under the disease incidence progress curve.

Efeito de fontes de silício na incidência e na severidade da antracnose do feijoeiro

ABSTRACTEffects of silicon sources on the incidence and severity of the common beans anthracnose Three e xperiments were performed to study the influence of the silicon on the reduction of the common bean ( Phaseolumvulgaris ) anthracnose. The first experiment involved a plant fertilized with calcium silicate and different inoculumconcentrations of the Colletotrichum lindemuthianum (0, 10 3 , 10 4 , 5x10 4 , 10 5 , 5x10 5 and 10 6 conidia/ml). In theconcentration 10 6 conidia/ml the difference b etween calcium silicate and calcium oxide was evaluated for effects on thedisease. The second experiment evaluated the influence of sodium and calcium silicate on the reduction of the anthracnose.In the third experiment, the scanning electron microscopy (SEM) and X-ray micro-analysis (EDAX) were used to study theeffect of the silicon on the plant resistance mechanism. Five evaluations of the incidence, severity and leaf area were done, i nthe first and second experiment. Disease evaluation was made using area under disease progress curve for incidence (AUDPCI)and severity (AUDPCS) and healthy leaf area duration (HAD). Inoculum concentration was found to increase the AUDPCIand AUDP CS. In contrast, the HAD had decreased. Fertilization of plants with calcium silicate significantly reduced the AUDPCIand AUDPCS, when compared to inoculated control and fertilized plants by calcium oxide (CaO) with higher inoculumconcentration. On the second trial, the application of sodium silicate on the leaves of the bean plant reduced AUDPCS by62,4% when compared to control. When the treated leaves were scanned with SEM and EDAX was performed, although thesilicon had reduced the disease, no accumulation of an external silicon barrier was observed with application of the element.

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

Relação nitrogênio/potássio com mancha de Phoma e nutrição de mudas de cafeeiro em solução nutritiva

This work was carried out to evaluate different dosages of N and K amended through roots via nutrient solution on the intensity of Phoma spot in coffee seedlings, and to determine the dry matter and the concentration of macro and micronutrients in the aerial part of coffee seedlings inoculated with Phoma tarda. Treatments encompassed 5 dosages of K (4, 5, 6, 7 and 8 mmol/L) combined to 5 dosages of N (3, 7, 11, 15 and 19 mmol/L), in 25 treatments and three replicates. This assay was repeated three times at 20oC. By increasing the amended N, there was a linear increase of 34.8% for AUIPC (Area under incidence progress curve) and 34.3% for AUSPC (Area under severity progress curve). By increasing the K, there was a square-shaped reduction for both AUIPC and AUSPC. The dry matter of coffee seedlings increased linearly with the increase in the amended N. By increasing the amended N, a corresponding increase in shoot N content was observed. Dosages of potassium significantly influenced the N, K, Ca, S and B contents in the shoot of coffee seedlings. Thus, balanced fertilization, besides minimizing nutritional problems, can be manipulated to reduce the number of fungicide applications in this pathosystem.

Adsorção e dessorção aniônicas individuais por gibbsita pedogenética

Anion adsorption/desorption dynamics was studied as individual processes on surface of particles of a gibbsitic clay. The data suggest a remarkable gibbsite role as nitrate leaching retardant in soil. The opposite behavior of gibbsite towards adsorption/desorption of silicate and phosphate suggests the need of an adequate compromise solution regarding interval and rate applications of anions in cultivated gibbsitic soils. The high P adsorption verified in pH values lower than that reported for the point of zero charge of synthetic Al-hydroxides implies that this process takes place in pedogenic gibbsites through inner sphere complexation.

Retenção e dessorção competitivas de ânions inorgânicos em gibbsita natural de solo

The objective of this work was to quantify the competitive retention and desorption of nitrate, sulfate, silicate and phosphate anions on gibbsitic clay fraction of a Melanic Gleisol. Samples of clay fraction were shaken in centrifuge tubes with 30 mmolc L-1 NaCl solution containing these anions in quantities equivalent to 30% of the respective maximum adsorption capacity exhibited by clay. For comparative purposes, samples were also shaken with the same solution containing 1 mmolc L-1 of each mentioned anion. The tubes were centrifuged and the anionic concentrations in supernatants were determined. The dessorption was performed by shaking the residual clay fraction in centrifuge tubes with NaCl solution and quantifying the released anions. In another experiment, with the silicon phosphorus previously adsorbed to gibbsite, P and Si were added in the sequence, intercalated for evaluating the capacity of desorpting the previously adsorbed anion. The phosphate was preferentially adsorbed in relation to the other studied anions and the previous silicon application reduced the phosphate fixation. The silicon application previously to phosphate favours the bioavailability of P in highly weathered soils.

Aumento da eficiência nutricional de tomateiros inoculados com bactérias endofíticas promotoras de crescimento

Plant growth-promoting endophytic bacteria can increase plant nutritional efficiency thus favouring its yield. With the purpose of evaluating the influence of 10 previously selected isolates of growth-promoting endophytic bacteria on the uptake, utilization and transport of nutrients by tomato plants, greenhouse experiments were installed. The hypocotyl was cut in order to apply the endophytic bacteria to tomato seedlings cultivar Santa Clara. Fifty five days after transplanting the upper portion of the cut seedlings, the plants were collected to determine the dry matter of the aerial parts and concentration of macro and micro nutrients. The concentration of N, P, K, Ca, Mg, Cu and Zn in the shoot and N, P, Mg and Mn in roots of inoculated plants differed from non-inoculated controls. Endophytic bacteria Micrococcus sp. (UFLA 11-LS) and Brevundimonas sp. (UFV-E49) were identified by sequencing of the 16S ribosomal DNA. The P uptake in plants inoculated with these isolates was higher than in the non-inoculated controls. Plants treated with the first isolate were more efficient in the use of N, P, K, Ca, Mg, S, Cu, Fe, and Zn. The highest concentration of N, P, K, Mg, and Zn were found in the shoot of plants inoculated with Brevundimonas sp. The results of this study indicate that these endophytic bacteria isolates may be employed to increase the nutritional efficiency of tomato plants.

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.