The potential of gamma irradiation on antioxidant capacity and genomic alterations in Calendula officinalis

There are lines of evidence that ionizing radiations such as gamma rays can cause different biological effects on plants. Marigold (Calendula officinalis L.) is a member of the family Asteraceae. It possesses profound amounts of active ingredients. The aim of this study was to evaluate the changes imposed upon different dose levels of gamma radiation on some features of Calendula officinalis such as antioxidant activity, total phenolic compounds and flavonoid contents, antibacterial activity and genomic alterations. Calendula officinalis seeds were exposed to different doses of Gamma radiation (0, 10, 15, 20 and 25 GY). Total phenolics, flavonoids, antioxidant activity (measured by DPPH assay) using methanolic extracts of plants and antibacterial activity measured by the disc diffusion assay showed significant differences to the control samples. The samples treated with 10 GY gamma rays showed the highest total phenol and flavonoid contents. Antioxidant activity significantly differed between Gamma rays dose levels and it was the highest at 25 GY. Four bacterial strains including E. coli, Bacillus subtilis and Pseudomonas aeroginosa were used for the antibacterial assay. Extracts from plants treated with 25 GY gamma rays showed the highest antibacterial activity against the 4 bacterial strains. Random amplified polymorphic DNA (RAPD) and inter-simple sequence repeat (ISSR) markers were used to study the genetic variation. The polymorphism information content (PIC) for RAPD primers ranged from 3% to 13% and ranged from 6 to 13% for ISSR primers. Results indicated that ISSR markers were more efficient than RAPD markers, as they detected 25.57% polymorphic DNA bands compared to 21.31% polymorphism for RAPD markers.