Abstract: The DNA polymorphism of the three host-related populations of Nilaparvata lugens, which differed in virulence and had been reared on rice variety TN1, Mudgo and ASD7 for 82 generations, respectively, was studied using RAPD-PCR technique. Of 205 RAPD primers, 10 with population-specific amplified bands were selected. The results showed that the genetic diversity among populations was greater than that within populations and the TN1 population reared on susceptible rice variety showed the largest genetic variation, although the differences between different populations were not statistically significant. In the dendrogram obtained with UPGMA analysis based on the standard of similarity index (SI), every female individual of a population could be clustered into a group with no exception, and so does the male. This provided the first clear evidence confirming that significant genetic differentiation exits between host-associated N. lugens populations with different virulence. It was also found that male and female individuals were grouped into two discrete classes, which suggested that the inheritance of virulence of N. lugens may be associated with the sex chromosome. Some amplified DNA bands were population-specific, which were useful to develop a molecular marker to examine the virulence of N. Lugens at the individual level.

Key words: Nilaparvata lugens (Stal), virulence, biotype, DNA polymorphism, RAPD-PCR