Effect of gamma irradiation on cyto-morphology, total phenolic content and antioxidant activity of calendula

Gamma ray irradiation is one of the best ways to induce mutation and increase genetic variability in plants. The present investigation was carried out to study the effect of gamma irradiation on cyto-morphological and phytochemical attributes in Calendula officinalis Linn and screening of novel mutants. The seeds of Calendula officinalis var. Fiesta Gitana Yellow were exposed to gamma rays (20, 40, 60, 80, 100, 120 and 140 Gy) treatment using ⁶⁰Co source, and un-irradiated seeds were used as control. Low doses of gamma irradiation resulted in hormesis and induced encouraging novelties, while the higher doses induced higher degree of abnormalities, which even led to mortality in many plants. In M1 generation, 10 mutants were screened and tagged, of which three promising mutants viz. C1 and C2 at 20 Gy and C3 at 40 Gy gamma irradiation, were found stable till M2 generation. They were screened for cytomorphological studies, phytochemical attributes (total phenolic content and antioxidant activity) and possible use of these novel traits (flower colour and plant height) as ornamental novelties, which can be released as a new variety after subsequent studies in further generations.