A comparison of the granulosis viruses from Pieris brassicae and Pieris rapae

The granulosis viruses of Pieris brassicae and P. rapae have been compared biochemically and biologically. No differences were found between virus capsules when examined by immunodiffusion, ELISA, or SDS-polyacrylamide gel electrophoresis. The virus particles were identical by immunodiffusion but distinguishable by ELISA. Comparison of virus particle polypeptides on SDS-polyacrylamide gels indicated small differences in molecular weight in three of the polypeptides of the virus envelope but no difference between the nucleocapsids. There were several differences between the DNA fragments produced by digestion with EcoRI, BamH1, and HindIII restriction endonucleases from which the homology between the two DNAs was calculated to be 97.7%. The small structural difference between the two viruses is associated with a very large difference in their virulence for P. brassicae; the LD50 with P. rapae GV being at least 1000 times greater than with P. brassicae GV. P. rapae was much more susceptible to either virus than P. brassicae and in this case the LD50 values were not significantly different for the two viruses.