IN VITRO INHIBITION ASSAY OF COPPER SULPHATE AS FUNGICIDE AGAINST WHITE THREAD BLIGHT FUNGAL ISOLATES

DOMINGUEZ FG; VERESCHUK ML; ZAPATA PD; ALVARENGA AE

Congreso; LVII SAIB Meeting - XVI SAMIGE Meeting; 2021

White thread blight is a disease caused by a fungal complex that causes drying of leaves, stems and branches in Yerba mate and tea plants and causes serious losses in the yield of these crops. Conventional synthetic fungicides are largely considered as the most effective and cost-efficient means for disease management. One of the most used broad-spectrum fungicides for the control of foliar diseases is copper sulphate pentahydrate. Sensitivity of the pathogens to copper varies greatly, depending on the product and the fungus. However, to date, no published studies are available on the inhibition/tolerance to copper sulphate concentrations of the white thread blight fungal isolates. This research investigated the grow inhibition of seven isolates (ACK2, AFE1, ASD4, AKD2, ACJ2, ACB1 and APC1) associated with white thread blight disease by the poisoned food method. Czapek agar medium was supplemented with copper sulphate pentahydrate (CuSO4.5H2O) at concentrations of 100ppm, 500ppm, 1000ppm and 5000ppm. Twenty milliliters of each sterile medium were dispensed into Petri dishes and inoculated with a 5mm disc cut from the periphery of a 7 days-old culture. Each isolate was inoculated onto two plates and incubated at 28°C. Mycelial growth of the isolates was determined by linear measurements of colony diameters with an electronic caliper at four intervals. To determine fungicide or fungistatic effect the discs which concentrations that completely inhibited growth were inoculated in Potato Dextrose Agar (PDA) medium. Three isolates (AKD2, ACB1, AFE1) showed a maximum inhibition of mycelial growth at 500ppm. Additionally, two isolates (ACK2, ACJ2) were inhibited at a concentration of 1000 ppm. Maximum effect of inhibition of growth was observed at the highest concentration at 5000 ppm. In fungicide/fungistatic assay we verified that at 1000 ppm copper sulphate acts as a fungistatic, inhibiting the development of the fungus but without causing its total elimination. These results suggest that white thread blight pathogens are sensitive to copper sulphate-based fungicides.