INFLUENCE OF CALCIUM PRETREATMENT ON PECTIC SUBSTANCE EVOLUTION IN CUCUMBER FRUIT (CUCUMIS-SATIVUS) DURING BOTRYTIS-CINEREA INFECTION

The role of calcium in protecting plant tissue from infection by Botrytis cinerea was studied in cucumber fruit. A self-defense reaction, consisting of an increase in cell-wall-bound Ca, occurred in the plant tissue after an injury or an infection. However, it was not sufficient to protect the tissue from the spread of the fungus, which is accompanied by pectic substance digestion. The degradation induced mainly a decrease in acid- and chelator-soluble pectin levels, and an increase in water-soluble pectin. Ca treatment of the fruit prior to infection could amplify the cell-wall-bound Ca and therefore lessen pectin digestion by fungal pectinolytic enzymes.