Cacti are important in agricultural economies and one of the most popular horticultural plant groups. The genus Astrophytum is one of the most valuable and desirable cacti for growers and collectors around the world. By selecting the appropriate breeding methods to induce variations in combination with modern biotechnology tools for rapid change detection, it is possible to meet the challenges of the modern world in creating new variability in plants. However, there exists a lack of research concerning the impact of ionizing radiation on cacti. The aim of the study was to assess the effects of X-rays at different doses (0 Gy—control, 15, 20, 25, and 50 Gy) on the dynamics of seed germination in vitro, changes in the color of seedlings, biochemical changes in the content of metabolites and changes at the molecular level in Astrophytum spp. ‘Purple’. A significant effect of X-rays on the induction of genetic variation was observed. Remarkably high polymorphism rates were observed, ranging from 59.09% for primer S12 to a full 100.0% for S3 and S8, as determined by the SCoT (Start-Codon-Targeted) marker. In addition, a large variation in the content of plant pigments (anthocyanins, carotenoids, chlorophyll a, and chlorophyll b) was noted. Additionally, discernible alterations in the color of the tested cactus seedlings, assessed by the RHSCC catalog, were attributed to the impact of ionizing radiation. These findings hold promise for the application of radiomutation breeding in acquiring new cactus cultivars.

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.