Tolerance of Four New Zealand Apple Cultivars to Disinfesting X-ray Treatment

Disinfestation of fresh commodities with X-ray radiation is an effective and accepted quarantine treatment for export markets, but fruit quality may be affected. In this study, we examined the effect of a range of X-ray doses on the quality of New Zealand–grown apple cultivars Royal Gala, Fuji, Scired, and Scifresh. Fruit were harvested and packed in New Zealand and transported to Hawaii for X-ray treatment at 150, 300, 500, 700, 1000, or 1400 Gy, cold-stored (0.5 °C) for 9 weeks, and assessed after 7 days at 20 °C. Higher X-ray doses resulted in lower fruit firmness for all cultivars compared with untreated controls, although significant differences did not occur until doses of 500 to 700 Gy. There were only minor to no significant effects on total acidity, soluble solids, or skin color. Internal browning was the only quality disorder observed in X-ray–treated fruit and was only significant in ‘Royal Gala’ at ≥700 Gy. Since the major quarantine insect pests of New Zealand apples are tortricid moths, which can be controlled at 250 Gy, irradiation with X-rays is a potential tool to achieve quarantine security and gain market access while maintaining fruit quality.