Effect of gamma irradiation on median lethal dose for mutation induction in Zinnia elegans and Cosmos bipinnatus

Zinnias and cosmos are popularly grown as decorative flowers in homes, gardens, and as potted plants. In this study, the appropriated gamma radiation doses for inducing mutations in zinnias and cosmos were investigated. It was found that gamma radiation significantly improved the seed germination parameters of both zinnias and cosmos. Vegetative growth traits showed that both zinnias and cosmos had decreased survival rate, fewer shoots, and reduced plant height as the irradiation dose increased. At a dose of 800 Gy, seeds were able to germinate, but seedlings grew to be stunted and eventually died. The median lethal dose (LD50) of zinnias and cosmos was determined as 459.6 and 345.5 Gy, respectively. Gamma radiation also affected the development of flowers as it delayed the flowering time in zinnias. In addition, gamma irradiation induced morphological changes in both plants, including stunted stems, curled leaves, smaller flowers and light green variegated leaves in zinnias, and the asymmetry and curling petals, in cosmos. Our findings provide crucial information for optimizing the gamma radiation dose to induce mutagenesis in zinnias and cosmos while minimizing other deleterious effects.