Induction of Physical Mutations in Gladiolus grandiflorus L. through Gamma Irradiation

Gladiolus is one of the most popular cut flowers cultivated in India, and it is excellent for inducing physical mutagenesis. The present study was carried out to determine the optimal lethal dose for gamma rays and to induce mutations through gamma irradiation in two gladiolus varieties, Arka Amar and Arka Thilak. The corms of both varieties were irradiated with gamma ray of doses 25, 40, 55 and 70 Gy using a gamma chamber with 60Co as the radiation source. The mortality rate of the plants increased significantly with increasing radiation doses, with Arka Thilak showing higher sensitivity. The LD50 (lethal dose) values were determined as 58.22 Gy for Arka Amar and 58.31 Gy for Arka Thilak through probit analysis. Based on the LD50, the effective doses were fixed as 45, 50, 55, 60 and 65 Gy, along with a control, for both varieties. Corms of gladiolus varieties were then treated with the selected doses of gamma radiation to induce physical mutation. Six treatments of each variety were evaluated in factorial completely randomized design with three replications. The characters like number of leaves per plant, length and diameter of the floret, and plant height were highest in Arka Thilak treated with 45 Gy. The number of spikes per plant and spike length were highest in the same variety treated with 50 Gy. In Arka Amar, the length of leaf blade and field life were maximum at 45 Gy, and a greater number of florets per spike was observed at 50 Gy. Among the treatments, lower doses promoted better growth, whereas higher doses had detrimental effects. Attractive colour mutants were obtained in Arka Amar at higher doses. The study suggest the ability of gamma irradiation to induce beneficial mutations in gladiolus, creating opportunities for breeding new varieties with improved ornamental traits.