Manganese and fluorine suppress bacterial blight on coffee seedlings grown in a nutrient solution

Abstract

The use of manganese (Mn) and fluorine (F) in the management of bacterial blight were evaluated in coffee seedlings grown in a nutrient solution. The experiment was carried out with the cultivar Catuaí Vermelho IAC 99. The treatments consisted of the combination of five doses of Mn with five of F, applied via leaf, using Mn sulfate and sodium fluoride, in a 5x5 factorial scheme. The plants were inoculated with bacterial suspension seven days after foliar application of F and Mn doses. The incidence and severity assessments were performed at an interval of 24 hours for 10 days. Photosynthetic activity was assessed using the infrared gas analyzer. Stomatal conductance, photosynthesis, transpiration, PAR radiation and internal CO2 were ana-lyzed. The chlorophyll content was calculated indirectly. The leaf analysis was performed by digestion in HNO3 to determine the levels of Mn. Variables such as Area Under Incidence Disease Progress (AUIDP), Area Under Severity Disease Progress (AUSDP), chlorophyll a, b, and total concentrations and photosynthesis were submitted to the Shapiro-Wilk test. The treatment means were subjected to linear regression analysis. Data were analyzed using software R. There was a significant interaction (P <0.05) between the concentrations of Mn and F for the AUIDP and (AUSDP). Doses between 0.7 and 1.4 g L-1 of Mn combined with doses of 0.10 to 0.12 g L-1 of F were more effective in suppressing the bacterial blight, after analysis for both variables. The increase in Mn concentrations in leaves reduced liquid photosynthesis. The interaction between Mn and F suppressed the bacterial blight intensity of the coffee plants in nutrient solution