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ABSTRACT
Wide variability does not exist in okra [Abelmoschus esculentus (L.) Moench], requiring induction of genetic variability. Mutagenesis creates desired variability among genotypes without altering the agronomic base which is sometimes difficult to induce using other breeding methods. Seed germination/seedling emergence and seedling growth were evaluated under laboratory and field conditions by imposing 300 to 1000 Gy (Gray, the SI unit of radiation) gamma radiation to determine median lethal (LD50) and median growth reduction (GR50) doses with Co60gamma rays. The LD50 and GR50 doses varied for both growing conditions. More than 80% of seed exposed to the LD50 dose of gamma radiation in the laboratory did not emerge under field condition. The LD50 and GR50 doses of gamma radiation determined under field condition exhibited close correspondence and presented a reliable picture regarding lethality and injury in the M1 generation (the first generation from the irradiated seed). The R2 for the linear model for seedling emergence, shoot and root length, fresh and dry weight of seedlings under field condition were 0.908, 0.902, 0.911, 0.983 and 0.972, respectively. Determination of the LD50/GR50 is important to optimize the radiation dose to isolate desired utilizable mutants. Dose optimization should be determined through use of LD50 and GR50 under field condition. The gamma radiation dose between 350 Gy and 450 Gy was optimum to create desirable mutants in okra. The optimal dose could induce a higher rate of mutation with little biological damage in succeeding generations of okra.
Acknowledgments
We thank the Board of Research in Nuclear Sciences, Department of Atomic Energy, Bhabha Atomic Research Centre, Trombay, Mumbai, India, for providing financial support to carry out this study.