Mutational studies on Chrysanthemum cv. ‘Maghi ’with particular reference to induction of flower colour mutation

Rooted cuttings of small flowered late blooming Chrysanthemum cv. ‘Maghi ’were irradiated with 0, 5, 10 and 15 Grays of gamma rays in gamma chamber model-900 a ⁶⁰Co source of Floriculture Section and planted in beds immediately after irradiation. Each treatment consisted of 25 plants. Reduction in survival, plant height, growth rate, plant spreadings-, (N-S and E-W), branch number, number of leaves and leaf size (length, width and petiole) and increased morphological abnormalities in foliage and flower were recorded after irradiation. LD₅₀ on survival basis was determined in between 10 and 15 Grays of gamma rays. Morphological abnormalities in leaves and plants increased after irradiation. Leaf abnormality includes asymmetrical development of leaf lamina, reduction in leaf size, notching of different grades, leathery texture, fission and fusion of leaf lamina, light and dark green leaves, sickle shaped leaf, narrow and linear leaf and obtuse apex. Fasciations in stem were also recorded after irradiation. Chimera in flower head colour was observed after irradiation. Frequency of chimera varies from a narrow yellow stripe on ray floret, half of the ray floret, full ray floret, bunch of ray floret on a flower head to entire flower head. In one plant all the flower head on a branch mutated in to yellow flower colour in M₁ V₁ and in another plant a branch produced striped (Yellow and White) flower head mutant. Attempts are being made to isolate this yellow flower mutant and stripped mutant (Yellow and White) in pure form. Three types of chimera in flower head colour viz. sectorial, mericlinal and periclinal were observed in treated population. Chimera management through tissue culture method and conventional method are in progress to isolate these mutants in pure form in M₂ V₂ and after wards release it as new cultivar.