Relative contribution of genetic and environmental factors to determination of wing morphs of the brown planthopper Nilaparvata lugens.

Wing dimorphism is a fascinating feature of the ability of insects to adapt to environments. The brown planthopper (BPH) Nilaparvata lugens, a serious pest of rice, can switch between the long- and short-winged morphs. It has been known that environmental factors can affect the wing morph of BPH. However, it is still unclear whether the effect of environment is dependent on BPH genetic backgrounds or not. In the present study, we established the pure-bred lineages of short- and long-winged BPHs via multigenerational selection, and we found that survival and fecundity were similar between these 2 lineages. Wing morphs of the pure-bred lineages were almost fully dependent on genetics, but independent of the environmental factors, nymphal density and rice plant stage, 2 key factors affecting BPH wing morphs. In the unselected BPH population, short- and long-winged morphs were produced depending on those 2 environmental factors, indicating the contribution of environment to wing morph. In the wing-selected lineages, 4 developmental regulated genes of wing, NlInR1, NlInR2, NlAkt, and NlFoxo were expressed stably in the short-winged adults, but almost silenced in the long-winged adults. However, all these genes were expressed normally with a similar level in both the short- and long-winged adults in an unselected population except NlFoxo. The pure-bred lineages of long- and short-winged morphs exhibited different expression patterns of wing development-regulated genes, suggesting the genetic determination of wing morphs. Effects of environmental factors on wing morphs occurred only in the genetic mix population.