Increase of coffee tree susceptibility to stem canker disease mediated by glyphosate application

Abstract

Stem canker is a major disease of coffee in Indonesia, caused by Fusarium solani. Previous studies showed a correlation between stem canker incidence and glyphosate application. The study aimed to determine the effect of glyphosate application on coffee stem canker and the underlying physiological mechanisms. The research used glyphosate treatments with the concentrations of 0, 4, 8, and 16 ml.L−1. In vitro experiments were carried out by measuring the growth of F. solani colony after glyphosate treatment. In planta, tests were conducted by artificial inoculation on glyphosate-treated coffee seedlings. The severity of stem canker was assessed. In a separate test, coffee seedlings were treated with glyphosate without pathogen inoculation. In the second experiment, physiological change was determined by measuring photosynthetic pigments, gas-exchange properties, lipid peroxidation, and activity of ascorbate peroxidase (APX) and catalase (CAT) enzymes. In vitro tests showed that glyphosate had antifungal activity against F. solani. In planta, the test showed that glyphosate treatment caused higher susceptibility to stem canker in coffee seedlings, indicated by the increase of canker wound depth. Glyphosate treatment on coffee decreased the chlorophyll, carotene contents, and reduced photosynthesis rate, caused oxidative stress depicted by higher lipid peroxidation and increased enzyme APX and CAT activity.