Application of mutation techniques to determine the optimum sensitivity dose for sorghum

Sorghum (Sorghum bicolor L.) is the fifth most important cereal crop of the world and serves as a major staple food and fodder resource, especially in arid and semi-arid regions. This crop has a big potential to be grown and cultivated owing to its wide adaptability and high productivity. However, sorghum still has low genetic variability; hence plant breeding programmes are required to support sorghum development. Induced mutations have been known to influence plant growth and development through induction of genetic, biochemical and morpho-genetic changes in plant cells and tissues. In Kenya induced mutations technology has not been adopted widely as a method of creating variability in crops. The objective of this study was to determine the optimal dosage ranges of gamma (γ-radiation) and X-rays irradiation for inducing mutations in Sorghum. In this study, the radio sensitivity of Seredo variety of Kenyan was used. A 60Co source for gamma irradiation and the RS-2400 Irradiator for X-rays irradiation were used for this study in 2012 Austria and study carried out in Kenya. A range of doses (control, 200, 400 and 600Gy) were used for mutation induction. The experimental design was randomised complete block with 4 replications. Seed bags containing 20 seeds were placed in desiccators containing 60% glycerol in order to equilibrate the moisture contents of the seeds (12-14%). Data was collected on physiological and morphological parameters of M1 at 14 days after planting and the survival rate at the maturity stage for both physical mutagens. For the Sorghum variety, there were 30 and 50% growth reductions, GR30 and GR50, respectively, at 14 DAP (Days after Planting) corresponded to 247 and 406 Gy for Gamma irradiation and 226 Gy and 349 Gy, for X-ray as deduced from the graphs trendlines. Fourteen DAP was determined as being the most informative for the effect of gamma and X-rays on plant growth in this study. The frequency of increased mutations correlated with the increase in radiation dosage. The survival rate declined to 32% for gamma and 0% for X-ray. Based on the findings, the optimum proposed dose for irradiating sorghum using physical mutagens is 200 to 400Gy.