Assessment of Mutagenic Sensitivity and Lethal Dose of EMS in Papaya (Carica papaya L.) variety CO 7

Mutagenesis is the process through which an organism's genetic makeup is irreversibly altered. The objective of this study was to determine the optimal ethyl methanesulfonate (EMS) dosage to create desirable genetic variations in the papaya variety CO 7.

The pre-soaked papaya seeds were exposed to five different concentrations of EMS (0.2%, 0.4%, 0.6%, 0.8% and 1.0%) for three hours. Non-treated seeds were used as a control. Data was recorded for germination per cent, seedling survival per cent, seedling length, girth, number of leaves, leaf length and width, petiole length and girth.

A declining trend in germination and growth of seedlings with the increase in EMS doses was observed. The probit curve analysis based on the seed germination percentage revealed that the LD₅₀ value was found to be 0.55% EMS which was fixed as an optimal dose for large-scale mutagenesis experiments in papaya variety CO 7. The R² value ranged from 0.73 to 0.99 and the growth reduction percentage (GR₅₀) varied from 0.69 to 1.16 for different seedling traits studied. Since the optimization of mutagen dose would be expected to create desirable mutations with nominal biological damage, this study might assist further mutagenesis experiments in papaya.