Metabolites, Nutritional Quality and Antioxidant Activity of Red Radish Roots Affected by Gamma Rays

Abstract

Radish is a root vegetable of the Brassicaceae family that is grown and eaten all over the world. It is often consumed raw as a crisp salad vegetable with a strong flavor. Therefore, this study aimed to clarify the stimulating effect of different γ-rays dose levels (0.0, 10, 20, 40, and 80 Gy) on the quality properties of radish, in addition to its nutritional elements, as well as some of the metabolites found in the red radish roots. The results indicated that the irradiated seeds showed a high germination rate of ≥96% for dose levels of ≤20 Gray (Gy). In addition, the use of gamma rays had a stimulating effect on the vegetative growth, particularly at the doses of 10 and 40 Gy, which provided the largest values of plant height (32.65 cm) and leaf number/plant (8.08), respectively, whereas all the irradiation treatments led to a rise in the length and width of leaves. However, the maximum root characteristics (length, diameter, size, and weight) were confirmed at the dose of 20 Gy (17.51 cm, 5.45 cm, 85.25 cm3 as well as 78.12 g, respectively). It was also noted that the content of plant pigments was significantly higher at a dose of 20 Gy. Additionally, there was an increase in the content of vitamin C using gamma rays, and the highest content (19.62 mg/100 g FW) was at the dose of 20 Gy. The use of γ-radiation caused an increase in some metabolite contents, such as anthocyanin, phenols, and flavonoids, which resulted in an enhancement in the antioxidant activity, achieving the greatest value at the dose of 40 Gy. Exposure of red radish seeds to gamma irradiation before cultivation improved the root contents of the elements (N, K, S, P, Ca, and Mg). The results indicated an increase in the content of organic acids (oxalic, succinic, and glutaric acids) using the radiation dose of 20 Gy, except for malic acid, which had the highest value at a dose of 80 Gy. Similarly, the amino acid pool was significantly increased by irradiation, and the levels of amino acids, which act as originators of the glucosinolate (GLS) phenylalanine, tyrosine and methionine), increased after exposure to gamma radiation, especially at doses of 40 and 80 Gy. Therefore, the red radish roots produced from seeds exposed to gamma rays were of high quality and nutritional value compared to those obtained from un-irradiated seeds. For this reason, gamma-rays are one of the tools that are utilized to improve the growth and quality of crops, especially in low doses.