Anatomical and biochemical changes in leaves of Vitis labrusca L. cv. Niagara Rosada in response to infection by Elsinoë ampelina Shear

The major grapevine cultivated in Brazil for in natura consumption is Vitis labrusca cv. Niagara Rosada, which it is considered susceptible to anthracnose. It is well-known that the pathogen infects preferentially immature leaves. To investigate quantitatively the anatomical and biochemical changes in leaves of Niagara Rosada cultivar after infection by Elsinoë ampelina Shear, healthy leaves at 4 and 11 days after sprouting (das) and infected leaves 7 days after inoculation with the fungus were analyzed, totaling 11 das. Scanning microscopy was used to compare healthy and symptomatic leaves surface morphology. Quantitative anatomical analyses were performed using light microscopy. The biochemical aspects included indicators of plant defense against anthracnose, such as total phenolic compounds, total flavonoids and enzymatic activities of peroxidase and polyphenoloxidase. The content of chlorophylls a , b , and total was also analyzed to verify the plant response to infection. All anatomical parameters analyzed showed lower values in inoculated leaves than those observed in the healthy leaves. Biochemical analyses indicated that the contents of total flavonoids (mgRE g −1 ) were similar between healthy leaves at 4 das (0.63 ± 0.01) and 11 das (0.63 ± 0.02), but inoculated leaves showed a higher concentration of flavonoids (0.75 ± 0.05). The polyphenoloxidase activity (U mL −1 ) varied between healthy and inoculated leaves, exhibiting the lowest activity in healthy leaves at 4 das (1.49 ± 0.10) and increasing in healthy (11.07 ± 0.23) and in inoculated leaves (15.20 ± 0.60) at 11 das. Polyphenoloxidase and peroxidase activity and flavonoids content increased after infection, but these increases were not sufficient to prevent disease advance.