CELL-WALL COMPOSITION OF CALCIUM-TREATED APPLES INOCULATED WITH BOTRYTIS-CINEREA

The role of calcium in maintaining cell wall integrity was investigated in cortical tissue of apple fruit. Carbohydrate, phenolic, protein and mineral element composition were determined in cell walls of high- and low-calcium content fruit inoculated with Botrytis cinerea. Cell walls in fungal-infected tissue of low-calcium fruit showed a decrease in non-cellulosic polysaccharides containing galacturonosyl, rhamnosyl, arabinosyl, xylosyl and galactosyl moieties and increases in cellulose, wall-bound phenolics, protein and mineral elements. In infected tissue of high-calcium fruit, the compositional changes in the cell wall were generally smaller compared with those observed in the low-calcium treatment. The results of this investigation indicate that the effect of calcium in reducing decay is associated with maintaining cell wall structure by delaying and/or modifying chemical changes in cell wall composition.