Nitenpyram resistance and IR56 feeding jointly drive the wing dimorphism in Nilaparvata lugens

Abstract

Nilaparvata lugens Stål is a significant insect pest of rice throughout Asia, and the use of insect-resistant rice varieties has been proposed as a key strategy to control this pest, and reduce reliance on insecticides. However, little is known about the interplay between these two methods, particularly their combined influence on the behavior, development, and reproduction. In this study, we found that both nitenpyram resistance in BPH and resistance in the rice variety to BPH jointly regulated wing dimorphism. A large proportion of long-winged BPHs (78%) were observed in the nitenpyram-resistant strain (NitR) when feeding on IR56, a BPH-resistant rice variety. No similar result in SUS (susceptible) insects was observed on either IR56 or TN1, nor in NitR insects on TN1. These results suggest that nitenpyram resistance and feeding on IR56 together regulated BPH wing dimorphism. Through quantitative analysis of hormone and insulin pathway genes, we found that a decrease in juvenile hormone (JH) and/or an increase in ecdysone (20E) induced the long-winged morph, accompanied by a reduction in the expression of insulin receptor 2 (InR2). Alterations in hormone levels and silencing InR2 could regulate wing morph differentiation. In males, JH III addition decreased long-wing proportion from 72 to 42%, while silencing InR2 increased long-wing proportion from 27 to 71%. This study suggests a potential risk that the insect-resistant rice variety may promote the spread of resistant insects, creating a contradiction in the combined use of insecticides and insect-resistant varieties.