âProgresso da cercosporiose e da ferrugem do cafeeiro (Coffea arabica L.) em funÃÃo da aplicaÃÃo de silÃcioâ / Progress of brown-eye spot and rust in coffee plants (Coffea arabica L.) treated with silicon.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The effect of adding silicon on the reduction of the brown-eye spot and rust intensities in coffee plants was evaluated in the present work in a set of four experiments. In the experiment 1, performed under field conditions, commercial silicon sources (A and B) were applied solely or in combination with fungicides: copper hydroxide, azoxystrobin and cyproconazole on the progress of brown-eye spot and rust in coffee plants from the cultivar Acaia Cerrado MG1474. The second experiment, carried out in greenhouse, aimed to verify the influence of silicic acid (doses 0; 0.5; 1; 2; 4 and 6 g kg â1 of soil) on the intensity of brown-eye spot and the mineral nutrition of coffee seedlings from the cultivar Catuaà Vermelho IAC 99. In the third experiment, the effect of silicic acid was studied in the same doses previously mentioned for the buildup of lignin, chlorophyll a and b, carotenoid quantities, photosynthetic potential, epidermal, cambium, phloem, xylem and spongy parenchyma widths and the presence of epicuticular wax in coffee seedlings from the cultivar Catuaà Vermelho IAC 99 inoculated with Cercospora coffeicola. The last experiment aimed to detect the presence of silicon in the cultivars Icatu Amarelo 3282 and TopÃzio MG1190 through X-ray microanalysis in seedlings sprayed with calcium silicate (1 g kg â1 of substract) and inoculated with C. coffeicola. The lower area under the progress curve of the number of lesions/leaf (AUPNLL) for brown-eye spot was observed for the treatment silicate A + Azoxystrobin in the field experiment. Treatments silicate A + silicate B, silicate A, silicate A + copper hydroxide, control and silicate B showed the area under the incidence progress curve of rust significatively higher than the other treatments. The use of silicate B significantly increased the AUPNLL and area under the severity progress curve (AUSPC) for rust. By increasing the silicic acid doses, a linear reduction on the AUPNLL of brown-eye spot was observed. The concentrations of phosphorus (P), magnesium (Mg), sulphur (S), boron (B), zinc (Zn) and copper (Cu) and as well as the contents of potassium (K), sulphur (S) and manganese (Mn) of shot dry weight were significatively influenced by silicic acid amendments to the soil. A mild epicuticular wax deposit was observed for the 2g-silicic acid dose (kg-1 of soil) and this was more evident at the dose 6 g kg â1 of soil. The use of the higher silicic acid dose (6 g kg â1 de soil) resulted in lower photosynthetic potential in the healthy seedlings. Peaks in silicon were not observed in any cultivar by the use of X-ray microanalysis however; lower potassium and calcium peaks were present in leaves from C. coffeicola-inoculated plants, when compared to leaves from healthy seedlings, in both cultivars.

ASSUNTO(S)

rust cafeeiro disease silÃcio coffee doenÃa ferrugem cercosporiose fitopatologia brown-eye spot silicon

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