Selection for imidacloprid resistance and mode of inheritance in the brown planthopper, Nilaparvata lugens.

BACKGROUND: Strong resistance to imidacloprid in Nilaparvata lugens (Stål) has developed in Southeast and East Asia. Although the mode of inheritance for resistance is very useful information for pest control, this information is unknown in N. lugens. Here, we established two resistant strains that were selected from field populations in Vietnam and the Philippines, and conducted crossing experiments to determine the inheritance pattern. RESULTS: The resistance ratio of 50% lethal dose (LD50 ) values for the two resistance-selected strains, i.e., resistant strains originating from Vietnam (VT-Res) and the Philippines (PH-Res), to their control strains were ∼ 8- and 157-fold, respectively. Reciprocal cross experiments between VT-Res and the susceptible strain (S-strain), and between PH-Res and the S-strain showed that the degree of dominance was 0.81 and 0.82, and 0.95 and 0.96, respectively. Analysis of the F2 populations and backcrosses to the parental strains indicated that resistance is a major-gene trait following Mendelian inheritance. The strength of the resistance was suppressed by pre-treatment with piperonyl butoxide, an inhibitor of cytochrome P450-monooxygenases. CONCLUSION: Our results suggest that imidacloprid resistance in N. lugens is autosomal and an almost completely dominant major-gene trait that is likely manifested by high expression levels of a detoxification enzyme. © 2019 Society of Chemical Industry.

Geographic and Research Center Origins of Rice Resistance to Asian Planthoppers and Leafhoppers: Implications for Rice Breeding and Gene Deployment.

This study examines aspects of virulence to resistant rice varieties among planthoppers and leafhoppers. Using a series of resistant varieties, brown planthopper, Nilaparvata lugens, virulence was assessed in seedlings and early-tillering plants at seven research centers in South and East Asia. Virulence of the whitebacked planthopper, Sogatella furcifera, in Taiwan and the Philippines was also assessed. Phylogenetic analysis of the varieties using single-nucleotide polymorphisms (SNPs) indicated a clade of highly resistant varieties from South Asia with two further South Asian clades of moderate resistance. Greenhouse bioassays indicated that planthoppers can develop virulence against multiple resistance genes including genes introgressed from wild rice species. Nilaparvata lugens populations from Punjab (India) and the Mekong Delta (Vietnam) were highly virulent to a range of key resistance donors irrespective of variety origin. Sogatella furcifera populations were less virulent to donors than N. lugens; however, several genes for resistance to S. furcifera are now ineffective in East Asia. A clade of International Rice Research Institute (IRRI)-bred varieties and breeding lines, without identified leafhopper-resistance genes, were highly resistant to the green leafhopper, Nephotettix virescens. Routine phenotyping during breeding programs likely maintains high levels of quantitative resistance to leafhoppers. We discuss these results in the light of breeding and deploying resistant rice in Asia.