Abstract: This paper deals with the effect of mutation on the Bornbyx rnori nuclear polyhedrosis virus (BmNPV) induced by mitomycin C (MMC) and dimethyl sulfoxide (DMSO) in the pupa of the silkworm. MMC is a mutagenic substance to BmNPV: (1) There was significant dosage effect upon the delay of infective period and the decrease of pupal mortality; (2) Morphological changes of the polyhedra were observed in some diseased pupae and their hereditary stability was testified in the next generation. Some polyhedra with extraordinary large size (15.0- 30.0 μm) having diagonal fission on the square surface were observed for the first time; (3) Structural changes were found within the mutated polyhedra and (4) The mutated BmNPV-DNA were digested by EcoRI, Bgl II and Bam HI, their electrotpherogram depicted the occurrence of some additional bands and the absence of other bands. These results show that MMC could induce the genome of BmNPV to mutate at many loci. DMSO does not induce mutagenesis in BmNPV with dosage below 9.0 μL/pupae.

Key words: silkworm, BmNPV, mutagenesis, MMC, DMSO