EFFECT OF SILICON ON THE INTENSITY OF BROWN EYE SPOT AND ON THE MINERAL NUTRITION OF COFFEE SEEDLINGS

ABSTRACT Our objective was to verify the effect of silicon on the intensity of brown eye spot and on the mineral nutrition of coffee seedlings. In the first experiment, 6 doses of silicic acid (0, 0.5, 1, 2, 4 and 6 g kg-1 soil) were tested using a complete randomized block design with 4 replicates with 6 coffee seedlings cultivar Catuaí Vermelho IAC 99 inoculated with the fungus Cercospora coffeicola. In the second experiment, X-ray microanalysis in a scanning electron microscope was performed on 2 coffee cultivars (Topazio MG1190 and Icatu Precoce IAC 3282), inoculated and non-inoculated with C. coffeicola, treated and untreated with calcium silicate (1 g kg-1 of soil). With the increase of the silicic acid doses, there was observed a reduction in the area under the disease progress curve of the number of lesions per leaf (AUPCNLL), coupled with a linear reduction in the foliar contents of magnesium and phosphorus as well as an increase in the contents of sulfur and copper. The foliar contents of boron presented a quadratic behavior, decreasing with the increase of silicic acid and increasing with the dose of 4 g kg-1 of soil. In X-ray microanalysis, coffee seedlings with brown eye spot presented lower peaks of potassium and calcium, regardless of the cultivar used.

摘要 本研究旨在验证硅对咖啡幼苗褐色眼斑病发病强度及其矿质营养状况的影响。第一项试验采用完全随机区组设计，设置4次重复，供试材料为6株卡特杜伊·韦梅略IAC 99（Catuaí Vermelho IAC 99）咖啡品种幼苗，以咖啡尾孢菌（Cercospora coffeicola）接种，共设置6个硅酸剂量梯度：0、0.5、1、2、4、6 g·kg⁻¹土壤。第二项试验针对两个咖啡品种——托帕齐奥MG1190（Topazio MG1190）与伊卡图早熟IAC 3282（Icatu Precoce IAC 3282），分别设置接种与未接种咖啡尾孢菌、施加与未施加硅酸钙（1 g·kg⁻¹土壤）处理，并利用扫描电子显微镜开展X射线微区分析。随硅酸剂量升高，单叶病斑数病程曲线下面积（AUPCNLL）显著降低；同时叶片镁、磷含量呈线性下降趋势，硫与铜含量则显著升高。叶片硼含量呈现二次变化规律：随硅酸剂量升高先降低，在土壤施用量为4 g·kg⁻¹时回升至峰值。X射线微区分析结果显示，无论供试咖啡品种为何，感染褐色眼斑病的咖啡幼苗叶片钾、钙元素的特征峰值均更低。