The Influence of X-ray Radiation on the Morphological, Biochemical, and Molecular Changes in Copiapoa tenuissima Seedlings

Cactaceae are a significant group of ornamental plants in the horticultural market. In the present study, X-rays were used for the first time to induce mutational changes in the cactus Copiapoa tenuissima. The aim of this study was to assess the genetic variability in seedlings exposed to in vitro X-ray irradiation at doses of 0, 15, 20, 25, and 50 Gy (radiation time from 5 min 13 s to 17 min 22 s) by morphological analysis, a spectrophotometric evaluation of plant pigment content, and the confirmation of changes at the genetic level using SCoT (start codon targeted) markers. The results showed that the percentage of colorful seedlings increased with the radiation dose and was the highest for the 50 Gy dose (4.89%). The radiation doses of 25 and 50 Gy generated seedlings with a new color (orange-brown), which had not yet been observed in C. tenuissima. With the increase in the radiation dose, as compared to control seedlings, brown seedlings showed an increase in the concentrations of carotenoids, chlorophyll a, and chlorophyll b, while green seedlings showed an increase in the concentrations of anthocyanins and chlorophyll b and a decrease in the concentrations of carotenoids and chlorophyll a. The unweighted pair group method analysis showed a very large genetic distance among the tested genotypes exposed to X-rays. The results of the present study provide a novel direction for using X-rays to breed new cultivars of C. tenuissima.