Mutation frequencies and chimeric formation in Phaseolus vulgaris after EMS treatment of dormant seeds

Dormant seeds of Ph. vulgaris were treated with 24, 48 and 72 mM solutions of EMS. The highest frequencies of mutations (chlorophyll, morphological and seed-coat color) were induced by the 48 mM dose. The M₁ plants were chimeric often having only a small mutated sector. Based on the segregation ratios obtained, the number of initial cells present in the apical meristem ranges from three to eight for the whole plant and from one to three for the primary branches. The experimental results indicate a post-treatment origin of the primary branch initials. No evidence was found for the occurrence of diplontic selection during the ontogeny of a mutated plant in the variety studied.