Gamma irradiation studies on callus and tissue culture to evolve improved sugarcane clones (Saccarum sp.) through induced somatic mutations. Part of a coordinated programme on improvement of vegetatively propagated crops and tree crops through induced mutations

Sugarcane variety, Co-547, which is highly susceptible to smut disease (Ustilago scitaminea Syd.) and is also late maturing, was exposed to different doses of gamma radiation to study its radiosensitivity and to induce smut disease resistance and early maturity. The radiosensitivity of the variety showed that an optimum dose (LD50) was 2.0 kR and working dose range was found to be 1.5-3.0 kR, while doses higher than 4.0 kR drastically affected the growth and germination. A broad spectrum of variability in reaction to disease resistance was observed after radiation exposure. This facilitated the isolation of disease resistant mutants. Twenty-three mutants showing varied reaction to smut under field infection conditions were tested by artificial inoculation using dip method for two years. From these studies 15 stable mutants were isolated. Of 15 mutants, seven showed promising performance in cane yield and sucrose contents. Tissue culture technique was used to determine the potential of different commercial clones for callusing. In test explants callusing was achieved readily and proliferation of callus was fairly good in all the clones