Gamma irradiation dose optimization in vegetative cuttings of damask rose ‘Meymand’ based on LD50 and GR50 for initiating mutation breeding programs

The appropriate gamma irradiation dose range for vegetatively propagated damask rose ( Rosa damascena Mill.) cuttings remains unclear. Therefore, this study evaluated the response of various gamma irradiation doses, which were considered as the main experimental factor, with 11 dose levels (0–100 Gy) and three replicates per treatment on damask rose cuttings in a completely randomized design (CRD), and measured traits including the cuttings’ ability to survive and their overall growth and morphological characteristics. The effect of gamma irradiation dose on the survival of cuttings was determined in the study. Survival was 100% in the control treatment and still relatively high at 10 and 20 Gy with 90.00% and 74.28% survival, respectively. Intermediate doses (30–60 Gy) showed survival rates of 50.00%–67.64%, while higher doses resulted in severe mortality with survival rates of 34.28% at 70 Gy and 8.57% at 80 Gy. Total mortality was observed at 90 and 100 Gy. Estimated lethal doses (LD) were LD 25 = 30.50 Gy, LD 50 = 51.69 Gy, and LD 75 = 68.40 Gy based on the selected complementary log-log binomial dose–response model. Estimated 50% growth reduction (GR 50 ) values were 37.88 Gy for leaf area and 28.48 and 26.45 Gy for fresh and dry weight, respectively. The combined LD 50 and GR 50 estimates can be used to establish a preliminary range of about 40–50 Gy gamma irradiation doses for further mutant induction and screening studies in damask rose cuttings.