POSTHARVEST CALCIUM TREATMENT OF APPLE FRUIT TO PROVIDE BROAD-SPECTRUM PROTECTION AGAINST POSTHARVEST PATHOGENS

Apple fruit (Malus domestica) were pressure infiltrated with calcium chloride solutions at harvest during three separate growing seasons. In 1984, the calcium concentration of Golden Delicious and Delicious apples ranged from 170 to 1,600 and 200 to 2,000-mu-g/g, respectively. In 1988, the calcium concentration of Delicious fruit ranged from 200 to 1,050-mu-g/g; similarly, that of Golden Delicious apples was 193-1,046-mu-g/g in 1989. Calcium concentration was negatively correlated with decay caused by the three different fungal pathogens tested during these three years. However, calcium reduced decay to a greater extent (70%) in fruit inoculated with Glomerella cingulata than in fruit inoculated with Penicillium expansum (37%) or Botrytis cinerea (50%). Thus, calcium-induced resistance to postharvest fungal pathogens is broad in spectrum.