Abstract Penicillium digitatum is a fungal pathogen, mainly responsible for postharvest decay of citrus fruits. Herein, we investigated the effect of gamma irradiation on fungal growth and postharvest physiology of Ponkan mandarin (Citrus reticulata Blanco). Preliminary results revealed that high dose gamma irradiation (> 1 kGy) severely damaged the fruit. Thus, we evaluated the effect of lower doses of gamma radiation (0, 0.25, 0.50, 0.75, 1.0 kGy) on disrupting the growth of P. digitatum, as well as on the postharvest quality of the Ponkan fruit. We found that there was an inverse dose-dependence to gamma irradiation-mediated inhibition of P. digitatum growth. Next, we examined the membrane integrity in the fungi that were exposed to gamma radiation to understand the underlying mechanism of the observed growth inhibition. The gamma irradiation disrupted the fungal membrane, resulting in the leakage of intracellular contents, such as sugars and proteins out of the damaged cells. Moreover, the irradiation impaired the metabolic functioning of malate dehydrogenase (MDH) and succinate dehydrogenase (SDH) within the tricarboxylic acid cycle (TCA) cycle. The overall results showed that at room temperature, the preservative effects of 0.25 and 0.75 kGy radiation were not evident, whereas 1.0 kGy resulted in rapid aging of the Ponkan fruit; 0.5 kGy was the optimal radiation dose to slow down the rate of fruit decay whilst decreasing the nutrient and weight loss in storage. Additionally, 0.5 kGy irradiation reduced the content of malondialdehyde (MDA), resulting in the improved activity of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD). Thus, these findings suggest that the optimal dosage of gamma radiation had the potential to extend the room temperature storage life of Ponkan fruit.

中文翻译：

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γ辐照对指状青霉的抑制作用及其在椪柑保鲜中的应用

摘要 指状青霉是一种真菌病原体，主要负责柑橘类水果的采后腐烂。在此，我们研究了伽马辐射对椪柑（Citrus reticulata Blanco）真菌生长和采后生理的影响。初步结果表明，高剂量伽马辐射（> 1 kGy）严重损坏了果实。因此，我们评估了较低剂量的 γ 辐射（0、0.25、0.50、0.75、1.0 kGy）对破坏 P. digitatum 生长以及对椪柑果实采后质量的影响。我们发现伽玛辐射介导的 P. digitatum 生长抑制存在反向剂量依赖性。接下来，我们检查了暴露于伽马辐射的真菌的膜完整性，以了解观察到的生长抑制的潜在机制。伽马辐射破坏了真菌膜，导致细胞内内容物（例如糖和蛋白质）从受损细胞中泄漏。此外，辐射损害了三羧酸循环 (TCA) 循环中苹果酸脱氢酶 (MDH) 和琥珀酸脱氢酶 (SDH) 的代谢功能。总体结果表明，在室温下，0.25和0.75 kGy辐射的防腐作用不明显，而1.0 kGy辐射导致椪柑果实快速老化；0.5 kGy 是减慢果实腐烂速度同时减少储存中的营养和重量损失的最佳辐射剂量。此外，0.5 kGy 辐射降低了丙二醛 (MDA) 的含量，从而提高了超氧化物歧化酶 (SOD)、过氧化氢酶 (CAT) 和过氧化物酶 (POD) 的活性。因此，