Allozyme variation among biotypes of the brown planthopper Nilaparvata lugens in the Philippines.

Allozyme variation was studied in three Nilaparvata lugens biotypes infesting specific rice varieties and a biotype infesting a weed grass, Leersia hexandra. Of the 20 enzymes in N. lugens for which activity was noted, 9 were polymorphic. Eleven enzyme loci were monomorphic for the same allele in all biotype populations; the rest were polymorphic for two or more alleles. The mean number of alleles per polymorphic locus was 2.3, while the mean number of alleles per locus was 1.5; heterozygosity ranged from 0.02 to 0.06 (biotype 1 greater than biotype 3 greater than Leersia-infesting biotype greater than biotype 2). Allelic frequency differences were observed in five loci among the four biotypes. However, the coefficient of genetic identity (I) of 0.99+ showed that the four biotype populations were genetically close relatives or merely populations of N. lugens undergoing genetic differentiation.