Effect of gamma radiations and ethyl methyl sulphonate on vegetative and Floral characters of chrysanthemum (Dandrenthema grandiflora L.)

Induced mutation is an important and fast tool of breeding in ornamental plants as the variation in phenotypic characters like flower colour, shape and size, and leaf variegation can be easily detected. In addition, the heterozygous nature of chrysanthemum offers high mutation frequency. An experiment to determine the optimum dose of mutagens required for inducing variability and to determine the level of LD₅₀ dose of mutagens in chrysanthemum cultivar Dolly Pink. The experiment comprised of two types of mutagens viz., ethyl methyl sulphonate (0.10, 0.15, 0.20 and 0.25%), and gamma rays (10, 20, 30 and 40 Gy) including control (no mutagenic treatment), laid out in randomized complete block design (RCBD) with three replications. Gamma rays (10 Gy) significantly improved most of the vegetative and flowering parameters by recording maximum plant height (40.54 cm), leaf length (5.62cm), leaf width (4.03 cm), number of branches per plant (30.80), stem thickness (3.74 mm), diameter of flower head (5.43cm), flower weight (1.71 g), pedicel length (4.50 cm), number of flowers per plant (42.33), flower yield per plant (57.31 g) and minimum days taken to appearance of first flower bud (49.63 days) and opening of first flower bud (77.59 days) as compared to control. On the other hand, EMS (0.10%) showed maximum plant spread (27.50 cm), branch length (26.90 cm) as compared to control. EMS was found to create more morphological variation in chrysanthemum than gamma rays. Two mutants with altered flower colour and one mutant with altered leaf morphology were obtained at 0.10 per cent and 0.15 per cent EMS, respectively. Whereas one leaf mutant was produced from gamma rays applied at 30 Gy. Based on probit analysis, LD₅₀ dose for gamma rays and EMS was found to be 26.57 Gy and 0.137 per cent, respectively.