Management of chimera and in vitro mutagenesis for development of new flower color/shape and chlorophyll variegated mutants in chrysanthemum.

Mutation breeding is an established method for crop improvement and has played a major role in the development of many new flower color/shape mutant varieties in ornamentals. The main bottleneck with vegetatively propagated plants is that the mutation appears as a chimera after treatment with physical and/or chemical mutagens. A small sector of a mutated branch or flower cannot be isolated using the available conventional propagation techniques. A novel technique has been standardized for the management of such chimeric tissues through direct shoot regeneration from chrysanthemum florets. This direct novel regeneration protocol has been successfully used not only for the isolation of chimeric mutant tissues developed through sports, but also to develop a series of new flower color/shape mutants through induced mutagenesis. Gamma radiation and tissue culture techniques have been optimized to regenerate plants from stem internodes, stem nodes, shoot tips and ray florets for in vitro management of chimera and for in vitro mutagenesis. Chimera isolation has practical importance not only for chrysanthemum but for breeding of other ornamentals also. The present technique will open up a new way for isolating new flower color/shape ornamental cultivars through retrieval of mutated cells.