Abstract
Mutagenic effects of ethyl methanesulphonate (EMS) on the cells in oogenesis of the silkworm (Bombyx mori L.) have been studied by a larval and pupal injection method. Germ-cells at the time of injection were from middle growth stage oocytes to pre-meiotic prophase I oocytes. Frequencies of mutations were estimated by the egg-color specific locus method using pe and re gene loci. A remarkable high mutagenicity was observed after EMS treatment of the late pupal prophase I oocytes. No marked mutagenicity of EMS was observed in larval growth stage oocytes. Simple mosaic mutants having mutant and non-mutant cells predominated in the progeny derived from EMS-treated late pupal prophase I oocytes. In this stage oocytes other types of mutations such as double mosaics having two mutant phenotypes, yellowish-white (pe) and red (re) cells, triple mosaics having three possible phenotypes, pe, re and +, and complete mutants were also observed. The results indicate that EMS might be mutagenic for pre-meiotic oocytes, egg pronuclei and cleavage nuclei.
