The Glomerella leaf spot (GLS) is an emerging disease and has become a major concern to Brazilian apple producers because the most widely grown cultivar, 'Gala', is highly susceptible to the disease. So, this study aimed to investigate the early stages of infectious process of C. gloeosporioides, and understand the role of peroxidase (POD) and β -1,3-glucanases (GLU) in susceptible ('Gala') and resistant ('Fuji') apple seedling genotypes. Seedlings (75 days-old) were inoculated with C. gloeosporioides and the severity of GLS was assessed at 10 days after inoculation. Conidial germination and appressoria formation of C. gloeosporioides were evaluated at 24, 48 and 72 hours after inoculation. Enzyme activity for POD and GLU were also determined at the same time interval. Seedlings of the resistant genotype did not show symptoms of GLS, whereas the susceptible genotype exhibited 11% of necrotic leaf area. The early penetration events of C. gloeosporioides were similar in both genotypes. Cultivar-specific resistance was associated with an enhanced POD activity, while GLU activity was similar in both genotypes.
Malus domestica; appressoria; peroxidases; β-1,3-glucanases; resistance
