Evaluation of Tissue Culture and Growth Assays to Identify Irradiated from Non-Irradiated Vegetables

Abstract

ABSTRACT Irradiation of foods is a process used to prevent sprouting of stored vegetables and to improve safety of food. Due to demand by consumers and many organizations to detect previously irradiated food, several methods have been tried to distinguish irradiated from non-irradiated food products. In this study, the ability of two tissue culture methods, callus or vegetative growth induction, to distinguish irradiated vegetables was evaluated. Potato tubers, carrot roots, garlic cloves, and onion bulbs were subjected to various gamma irradiation doses (0–1000 Gray (Gy)). Subsequently, the irradiated vegetables were grown in a controlled environment or explants excised for in vitro culture. Gamma irradiation significantly reduced callus-forming ability, especially in carrot and potato where no callus was observed for doses higher than 50 Gy. Length of shoots and roots growing from irradiated garlic and onion explants was considerably reduced starting with the 25 Gy dose. No roots formed on garlic explants at any irradiation dose. Garlic leaves growing from irradiated explants had purple to brown spots. Their intensity increased as gamma ray dosage increased. In the growth assay experiment, potato plants appeared only in the control (0 Gy) treatment. In contrast, a complete sprouting of garlic and onion was seen in all irradiation treatments. Therefore, it was not possible by the growth assay experiment to distinguish between the various irradiation treatments and the control 3 days after planting in pots. The two in vitro assays, tested in our study, may be used to distinguish the levels of irradiation on the vegetables tested. Callus formation was found more useful for potato and carrot, since regeneration of shoots in vitro from these two plants takes a long time. On the other hand, the growth assay is very useful for onion and garlic since it is rapid, sensitive and easy to perform.