Genetic structure reveals migration of the rice brown planthopper, Nilaparvata lugens Stål (Hemiptera: Delphacidae) from China to Japan

The brown planthopper (BPH), Nilaparvata lugens is one of the most serious and detrimental rice pests found in many rice-growing regions of the Asia including Japan. This species is wing-dimorphic (brachpterous, non-migratory and macropterous, migratory), and migrate Japan annually during rice seasons with assistance of the monsoon winds where it reproduces enormously and causes substantial economic losses. We have recently clarified at molecular level by cloning/characterizing the yolk protein precursor gene, vitellogenin (Vg), that the reproductive strategies are delayed in macropterous females to ensure the pre-reproductive long distance migration. In present studies, we analyze genetic structure among various BPH populations to understand better the origin of this pest invasion into Japan. For this an 812 bp region of the mitochondrial DNA cytochrome c Oxidase I (COI) gene was analyzed from a total of 11 populations collected from three countries (Vietnam: 5, China: 2, and Japan: 4). The sequence analysis indicated that nine haplotypes of BPH were found in Vietnam, two in Japan, two in China while all populations shared a dominant haplotype. In populations sampled from Vietnam and China variation was observed even with the populations suggesting a regular mixing of the gene flow. However, no variation was observed within the populations collected from Japan. Population from China did share haplotype found in Japan, suggesting that China was the source for the yearly migration of this pest into Japan.