Sensibilidad in vitro de Neoscytalidium spp. agente causal del cáncer de la pitahaya a fungicidas de diferentes modos de acción.

Abstract

The objective of this research was to determine the in vitro sensitivity of Neoscytalidium spp. the causal agent of pitahaya cancer to fungicides of different modes of action. Therefore 12 active ingredients were used, according to the classification of the Fungicide Resistance Action Committee (FRAC). There were three active ingredients from the respiration group, two from membrane sterol biosynthesis, two from motor and cytoskeleton proteins, one from amino acid and protein synthesis, one from chemicals with multi-site activity, one from plant host defense induction, one from lipid transport or synthesis/membrane function or integrity, and one from unclassified. Nine strains isolated from pitahaya cultivars from the Guayas and Los Ríos provinces were used. Calculations were made based on an initial concentration from which sequential dilutions were carried out to obtain each of the doses established in the research (0; 0.1; 1; 10; 100; 500 ppm), with which a solution with PDA medium was created and Neoscytalidium spp. discs were transferred, from which diameter measurements were taken every 24 hours. The results obtained were tabulated in Excel and then entered the RStudio program for the descriptive statistical analysis of the Effective Dose 50 (DE50) showing strains with sensitive ranges in the products methyl thiophanate with 7 strains (87, 5%), tebuconazole with 5 strains (55.55%), thiabendazole, difenoconazole, and azoxystrobin with 3 strains each (33.33%) and pyraclostrobin with 2 strains (22.22%). It was concluded that at DE50, boscalid and copper sulfate showed resistance at all the doses studied. It is recommended that other active ingredients with the same mode of action used in this study be tested to determine whether cross-resistance exists.