Decay caused by Botrytis cinerea is significantly reduced by increasing the calcium concentration of apple fruit tissue. Electron microscope studies have revealed that cracks in the epicuticular wax may be an important pathway by which calcium penetrates into the fruit and increases the calcium concentration. In fruit inoculated with B. cinerea, the decay induced compositional changes in the cell walls of high-calcium fruit were smaller than those observed in the low calcium treatment. The effect of calcium in reducing decay is associated with maintaining cell wall structure by delaying chemical changes in cell wall composition. B. cinerea produced five polygalacturonase isozymes in vitro but only one in vivo. Among the cations studied-m was the most potent inhibitor of polygalacturonase activity in in vitro studies. Its mode of inhibition appears to involve the alteration of substrate availability for hydrolysis, rather than any direct effect on the active sites of the enzyme.
1046 EFFECT OF POSTHARVEST CALCIUM TREATMENT OF APPLES ON POLYGALACTURONASE PRODUCED BY BOTRYTIS CINEREA.
