Resumo:
Rust, caused by Hemileia vastatrix, is the main disease that decreases coffee production in Brazil. New and enhanced methods to reduce rust intensity that can be integrated with modern genetic and chemical approaches need to be investigated. Considering that many plant species supplied with silicon (Si) show increased resistance to several pathogens, this study examined the possible effect of this element in increasing chlorogenic acid (CA) concentrations in coffee leaves and, consequently, increasing the level of resistance to rust. Plants (cv. “Catuaí Vermelho IAC 44”) were inoculated with H. vastatrix after growing for 35 days in a hydroponic culture amended with 0 (-Si) or 2 (+Si) mM Si. Concentration of Si in leaf tissues was of 0.36 and 0.42 dag/kg for -Si and +Si treatments, respectively, but without a statistically significant difference. The area under rust progress curve was 154.5 and 119.4 for -Si and +Si treatments, respectively, but without significant statistical difference. For non-inoculated plants, the concentrations of total CA and caffeoyl-quinic acid (CQA) compounds (diCQA) were similar between -Si and +Si treatments. Even though there was an increase of 236.4 and 257.1%, respectively, for total CA and diCQA for +Si when compared to -Si treatment at 30 days after inoculation with H. vastatrix, reduction on rust severity was not obtained once the fungus had already colonized the leaf tissues. Therefore, regardless of the increase in the concentrations of chlorogenic acid on leaves, coffee resistance to H. vastatrix infection was not potentialized by Si.
