Fruit maturity and calcium affect chilling requirements and ripening of 'd'Anjou' pears

Abstract

'D'Anjou' pear (Pyrus communis L.) trees were sprayed with zero or 32.3 mM CaCl2 during fruit development at 55, 86, 125, and 137 d from full bloom and harvested at 85% (immature), 100% (mature), and 110% (overmature) maturity stages. The fruit were stored in air at -1 °C for several periods to determine the effect of CaCl2 treatments on chilling requirement to accomplish ripening during 11 d at 20 °C. Immature or mature unsprayed fruit required 55 d, while the overmature fruit required 40 d at -1 °C to gain the capacity to produce ethylene during ripening at 20 °C. Calcium sprays increased flesh firmness at harvest by 15 N, fruit Ca concentrations by an average of 0.01 mg · g-1, fresh mass basis, and the chilling requirements by at least 15 d. Unsprayed immature fruit contained more Ca than the sprayed mature or overmature fruit, but their chilling requirement was similar. These results suggest that high Ca concentrations may increase the chilling requirement of 'd'Anjou' pears in a developmentally related manner.