Maintenance and Selection of Strains Exhibiting Specific Wing Form and Body Colour under High Density Conditions in the Brown Planthopper, Nilaparvata lugens (Homoptera: Delphacidae)

Abstract

Selections more than over 25 successive generations for specific wing form and body colour under low-density rearing conditions in Nilaparvata lugens failed to produce pure-bred lines with those characters. However, selections over 12 to 30 successive generations under high-density rearing conditions were successful in obtaining various lines predominantly producing specific wing form and body colour over a board range of nymphal densities in both sexes: totally brachypterous lines with yellowish brown or highly melanized body colour and totally macropterous lines with highly melanized or yellowish brown body colour. Thus, wing form and body colouration are controlled by different genes. By successive selections based solely on wing form, two lines producing predominantly brachypterous or macropterous wing forms were obtained, but they exhibited an intermediate body colour between yellowish brown and black. When five field-collected strains were reared under high density conditions, their wing form and body colour responses to rearing density remained unchanged for more than over 20 generations. On the other hand, maintenance of these strains under low density conditions rendered them to exhibit considerable different responses from original ones, even though no special selection has been given. These results suggest that genetically controlled characters can be stably exhibited under high density conditions, while phenotype expression under low density conditions is largely influenced by the physiological situation of the individual hoppers. © 1992, JAPANESE SOCIETY OF APPLIED ENTOMOLOGY AND ZOOLOGY. All rights reserved.