اثر بازدارندگی پرتودهی گاما و NaDCC برای کنترل پوسیدگی کپک سبز نارنگی پس از برداشت

Tangerine production has been steadily increasing in recent years, but decaying after harvesting fresh fruits caused by green mold (Penicillium digitatum) is a serious problem affecting the marketability of this crop. This pathogen has a relatively short disease cycle and produces large numbers of aerial asexual conidia. Spores on the surface of the fruit germinate quickly under suitable conditions and colonize the damaged tissue. Therefore, they easily contaminate the fruits in the garden, at the time of packing and during marketing. Benzimidazoles have always been suggested to control fungal pathogens after harvest. However, the continued use of chemical fungicides is limited due to the development of fungal resistance and increasing public concerns about the environmental problems of chemical residues. Thus, different alternative methods have been introduced for it, and radiation is one of them. In this study, gamma radiation was evaluated for its antifungal activity in vitro and in vivo against Penicillium digitatum on tangerine fruits. Green mold was inhibited in a dose-dependent manner. Gamma irradiation showed complete inhibition of spore germination, elongation of the germ tube, and mycelium growth of P. digitatum at 1.0 kg Gy. To further investigate the mechanisms by which gamma irradiation inhibits fungal growth, membrane integrity and cell leakage of conidia were tested, displaying that gamma irradiation leads to loss of plasma membrane integrity and release of intracellular contents such as soluble proteins. In vivo assays showed that high doses can completely inhibit the growth of fungal pathogens, but cause severe fruit damage. Therefore, to eliminate the negative effect on fruit quality, gamma radiation at lower doses was evaluated for pathogen inhibition in combination with a chlorine donor, sodium dichlorostriazintrione (NaDCC). Interestingly, only a combination treatment with 0.3 kGy of gamma radiation and 8 ppm of NaDCC exhibited significant synergistic antifungal activity against green mold decay. The mechanisms by which the combination treatment reduces the green mold decay of tangerine fruits can be directly related to the disruption of the cell membrane of the fungal pathogen, which leads to the loss of cytoplasmic material from the hyphae. These findings suggest that the synergistic effect of combining treatment with gamma irradiation with NaDCC as an antifungal approach can potentially reduce the severity of green mold in this crop.