The major method for control of coffee leaf rust, caused by Hemileia vastatrix, is the use of fungicides. The supply of silicon (Si) to plants is an interesting control strategy because this element can increase the resistance of many plant species to pathogens. This study aimed to evaluate the effect of foliar application of Si on reducing rust severity as well as to determine if it can potentiate the activity of enzymes related to host resistance to pathogens. Coffee plants (cultivar Catuaí Vermelho 44) were sprayed with distilled water, potassium silicate (KSi) solution (35 g/L, pH 10.5), KSi (35 g/L, pH 5.5), and acibenzolar-S-methyl (ASM) solution (200 µg/L) 24 hours before inoculation. There was no significant difference among the treatments regarding the content of Si and potassium in the leaf tissue. Rust severity was significantly higher on plants sprayed with water as compared to the other treatments. The ASM significantly decreased rust severity by 70% in comparison to the water spray treatment. Foliar application of KSi, regardless of the pH, was efficient in decreasing rust severity. The ASM was efficient in increasing the activity of chitinases and β-1,3-glucanases. On the other hand, the application of KSi, regardless of the pH, was inefficient to potentiate the activity of these six enzymes studied, even though it had a great impact on reducing rust severity.
Hemileia vastatrix; biochemical mechanism of host defense; mineral nutrition
