Green mold, a predominant disease of citrus fruit, develops when spores of Penicillium digitatum infect extant wounds in fruit epidermal tissue. Development of green mold during shipping limits the distance grapefruit can be surface transported. The objective of this research was to evaluate whether altering the atmosphere during refrigerated storage could suppress development of green mold. In the first two experiments, growth of green mold was evaluated after fruit were stored in ultra-low oxygen (0.05 or 1 kPa) at 14, 16, or 18 °C for up to 21 days. In the last two experiments, grapefruit were stored for 14 or 21 d at 12, 13, or 14 °C in atmospheres containing 2, 5, or 10 kPa oxygen with or without 2, 5, 10, or 20 kPa carbon dioxide. In all experiments, grapefruit were inoculated with 10 or 20 μL of a spore suspension of P. digitatum. Decay progression after storage was monitored by measuring the diameter of the lesion in cm at the demarcated site of inoculation or by subjectively rating percent decayed fruit surface area. Grapefruit not inoculated with P. digitatum had no visible symptoms of green mold. Grapefruit stored under controlled atmosphere had less fruit surface covered with mycelium (5% to 64%) than grapefruit stored in air. Inoculated grapefruit stored in 0.05 kPa oxygen for up to 14 d at 14 or 18 °C had no visible symptoms of green mold upon removal from cold storage, but developed a characteristic green mold lesion after 5 additional days of storage in air at ambient temperature. Results suggest that refrigerated controlled-atmosphere storage combined with wax and a fungicide can enhance control of green mold during shipping.
Controlled atmosphere storage of New Zealand fruit: Effects of low oxygen and varying carbon dioxide levels