The effect of inoculum dose on the genetic diversity detected within Helicoverpa armigera nucleopolyhedrovirus populations

Environmental and infection variables may affect the genetic diversity of baculovirus populations. In this study, Helicoverpa armigera nucleopolyhedrovirus (HearNPV) was used as a model system for studying the effects of a key infection variable, inoculum dose, on the genetic diversity within nucleopolyhedrovirus populations. Diversity and equitability indices were calculated from DNA polymerase-specific denaturing gradient gel electrophoresis profiles obtained from individual H. armigera neonate larvae inoculated with either an LD5 or LD95 of HearNPV. Although the genetic diversity detected in larvae treated with an LD95 was not statistically different from the diversity detected in the HearNPV inoculum samples, there was a statistically significant difference in the genetic diversity detected in the LD5-inoculated larvae compared with the genetic diversity detected in the HearNPV samples used for the inoculations. The study suggests that inoculum dose needs to be considered carefully in experiments that evaluate HearNPV genetic diversity or in studies where differences in genetic diversity may have phenotypic consequences.