Estudio de la patogenicidad y agresividad de hongos filamentosos asociados a manchas circulares necróticas en cladodios de tuna (Opuntia ficus indica).

Abstract

The goal of this research was to study the pathogenicity and aggressiveness of filamentous fungi associated with circular necrotic spots on prickly pear cladodes (Opuntia ficus indica). We started with the reactivation of fungal strains of Cladosporium sp.; Dipodascus australiensis; Alternaria alternata strains 3 and 6; Fusarium incarnatum-equiseti; Fusarium oxysporum strain 4,8 and 9; Epicoccum spp. these were grown on a PDA medium for 15 days. Inside the laminar flow chamber, discs were cut from the mycelium with sterile sorbet segments, and five mycelial discs were added per 250 mL Erlenmeyer with V8 medium and transferred to the Orbital Shaker- Incubator, for three days. Finally, the spore count of the fungal isolates was performed, allowing adjustment to the spore concentration of 1x106. Inoculation of the cladodes was conducted by three methods: puncture, abrasion, and without a wound. Of the nine isolates inoculated on prickly pear cladodes, six were pathogenic (Dipodascus australiensis, Alternaria alternata strain 3, Alternaria alternata strain 6, Fusarium incarnatum-equiseti, Fusarium oxysporum y Epicoccum spp.). As a result, of pathogenicity and aggressiveness tests on prickly pear cladodes, the following were reported as pathogenic: Dipodascus australiensis, Alternaria alternata, Fusarium oxysporum, Fusarium incarnatum-equiseti. The most aggressive isolates were Fusarium oxysporum strain 4 with 12.37 mm and Alternaria alternata with 13.07 mm lesion diameter, respectively. It was concluded that this research is the first contribution using morphological and molecular characterization in Ecuador of fungi causing circular necrotic spots on prickly pear cladodes. It is recommended to conduct inoculations at different spore concentrations.