Radiation Disinfection Threshold of Botrytis cinerea Under X-ray and Gamma Irradiation

Radiation-based disinfection is a validated approach for controlling microbes and plant pathogens in agriculture and the food chain. Botrytis cinerea, a major necrotrophic pathogen of many crops, is a pertinent target for such non-chemical treatments. Here, we compared the effectiveness of gamma and X-ray irradiation with an emphasis on dose rate as a process variable, and assessed survival/regrowth on potato dextrose agar and loss of pathogenicity on strawberry fruit. At a fixed total dose of 6 kGy, gamma irradiation showed a clear dose-rate dependence: 0.5 kGy h⁻¹ permitted regrowth within 28 days, 1.0 kGy h⁻¹ resulted in lagged regrowth beginning after day 14, whereas 2.0 kGy h⁻¹ yielded no regrowth during the observation period. X-ray treatment at 6 kGy (≈2.5 kGy h⁻¹) likewise resulted in no colony expansion for a period of up to 28 days. Culture negativity was concordant with loss of pathogenicity on strawberries, supporting culture negativity as a practical disinfection endpoint. Collectively, these results indicate that, under our conditions, the critical disinfection dose (D_crit) for B. cinerea is ≤6 kGy when delivered at ≥2.0 kGy h⁻¹ (gamma) or at approximately 2.5 kGy h⁻¹ (X-ray), and that dose rate materially modulates survival/repair dynamics at a given total dose. This study defines process windows for effective application of irradiation and supports the practical deployment of radiation disinfection for quarantine and postharvest management of B. cinerea.