The genetic basis of oviposition preference differences between sympatric host races of the brown planthopper (Nilaparvata lugens)

We have previously analysed the genetic architecture of host–associated performance differences between stocks of the brown planthopper, Nilaparvata lugens (Homoptera: Delphacidae), derived from two host plants: cultivated rice variety TN1 and the semi–aquatic weed Leersia hexandra. It has been established that performance is influenced by a small effective number of loci (1 to 3), with dominance in the direction of the rice population. The results reported here show that, like performance, oviposition preference has a simple genetic basis, but in this case there is no evidence of directional dominance, sex linkage, non–allelic interaction or genotype–environment interaction. The simple genetic architecture of host–associated performance and oviposition preference are as expected if there was a sympatric host shift, most probably from Leersia to rice. However, contrary to the theoretical expectation from models of sympatric host–race formation, there was no detectable genetic association between the traits. The fact that individual females tend to distribute their eggs between plants may have helped to promote a host shift despite this lack of association.