Pre-harvest application of calcium to control black heart disorder in Mauritius pineapples during low-temperature storage

The chill-sensitive pineapple cv. Mauritius grown in Sri Lanka was subjected to different pre-harvest calcium treatments in order to determine an effective means of increasing calcium levels in the fruit, thereby reducing the incidence and severity of black heart disorder. Treatments of CaO and CaSO4 (10 g and 15 g per plant) were applied to soil as side dressing 6 weeks after planting, while CaCl2 (1.3 g and 2 g per fruit) were applied as a spray treatment to 1-month-old fruit (red bud stage). Fruit were harvested at the 10-20% yellow stage of maturity. Incidence of black heart disorder and observations on total acids, degrees Brix, ascorbic acid content and total calcium levels were recorded on waxed and unwaxed fruit before and after 17 days storage at 10 degrees C and 85-90% relative humidity, followed by 2 days at ambient temperature 28 2 degrees C. Combined treatment of pre-harvest CaCl2 fruit spray (1.3 g per fruit) followed by post-harvest wax treatment showed 80% good fruit with no black heart symptoms after low-temperature storage at 10 degrees C for 17 days followed by 2 days at ambient temperature of 28 +/- 2 degrees C. However, side dressings of CaO and CaSO4 were found to be less effective in reducing the symptoms, showing less than 30% of good fruit without black heart symptoms. Both core and flesh regions of pineapples subjected to pre-harvest fruit spray treatment showed higher total calcium levels compared to controls as well as other calcium treatments. Results obtained from the field experiment confirmed that the calcium chloride fruit spray treatment of 1.3 g per fruit in three split doses at 2-week intervals could be used to reduce the incidence of black heart disorder in Mauritius pineapples. (c) 2005 Society of Chemical Industry.