Qualitative Mutations Induced by Ethyl Methane Sulphonate in Phaseolus lunatus L.

Background and Objective: Phaseolus lunatus commonly known as lima bean is an underutilized crop in Nigeria, which possess the potential to serve as an alternative source of protein supply but yet no considerable efforts have been made in time past towards the genetic improvement of this crop. This study was undertaken to assess the efficiency of ethyl methane sulphonate in inducing morphological and physiological mutations in lima bean, thus increasing the genetic variation available in the gene pool which can serve as an important source of variant genes for further breeding. Materials and Methods: Landraces of Phaseolus lunatus were obtained, presoaked in distilled water for 6 hrs and treated with freshly prepared concentrations of ethyl methane sulphonate (0.1, 0.2, 0.3 and 0.4%) for 6 hrs, a control experiment was also set up. Treated seeds and control were sown in polythene bags filled with top garden soil and arranged using a randomized complete block design to raise the M₁ and M₂ generation. Results: Morphological mutants: Invaginated leaf margin, bifurcated leaf apex, biapex leaf and enlarged leaf were observed in M₂ mutants treated with 0.2, 0.3 and 0.4% of the mutagen. Physiological mutants: A change in seed coat color from brown to black with off-white patches and a change in flower color from yellow to purple was observed in M₂ mutants treated with 0.4% ethyl methane sulphonate. The percentage frequency of M₂ progenies segregating for seed coat and flower color change was 92.31%. Conclusion: However, this research concludes that 0.3 and 0.4% ethyl methane sulphonate are more effective at inducing morphological and physiological mutations in Phaseolus lunatus.