Species-specific markers for Nilaparvata lugens and Sogatella furcifera (Hemiptera: Delphacidae) based on mitochondrial cytochrome oxidase I.

Brown planthopper (BPH), Nilaparvata lugens (Stål) and white-backed planthopper (WBPH), Sogatella furcifera (Horváth) are the most destructive sucking insect pests of rice in all rice growing parts of the world. For their accurate identification at early stages, we have developed two species-specific markers (SNL4F and SNL4R for BPH; SNF2F and SNF2R for WBPH) based on mitochondrial cytochrome oxidase I (COI) for their easy detection using Polymerase Chain Reaction (PCR). The markers were developed based on nucleotide differences in COI gene and were subjected to various tests based on PCR-based gel images. The designed primers were cross-checked with five other species, which confirmed their specificity. The primers were also found to be efficient in identification of their respective species (BPH and WBPH) in all the individuals sampled from different regions of India. The lowest detection sensitivity of both the primers was up to 1 ng/µl DNA after testing them through a series of varied DNA concentrations. The species-specific primers developed in this study will help in easy and rapid identification of BPH and WBPH in all the stages of their development and in turn facilitate their timely management. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03693-x.

Fitness costs of resistance to insecticides in insects.

The chemical application is considered one of the most crucial methods for controlling insect pests, especially in intensive farming practices. Owing to the chemical application, insect pests are exposed to toxic chemical insecticides along with other stress factors in the environment. Insects require energy and resources for survival and adaptation to cope with these conditions. Also, insects use behavioral, physiological, and genetic mechanisms to combat stressors, like new environments, which may include chemicals insecticides. Sometimes, the continuous selection pressure of insecticides is metabolically costly, which leads to resistance development through constitutive upregulation of detoxification genes and/or target-site mutations. These actions are costly and can potentially affect the biological traits, including development and reproduction parameters and other key variables that ultimately affect the overall fitness of insects. This review synthesizes published in-depth information on fitness costs induced by insecticide resistance in insect pests in the past decade. It thereby highlights the insecticides resistant to insect populations that might help design integrated pest management (IPM) programs for controlling the spread of resistant populations.

Migratory behaviour of Brown planthopper, Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), in India as inferred from genetic diversity and reverse trajectory analysis.

The brown planthopper, Nilaparvata lugens (Stål) is a major sucking insect pest of rice. This insect has long been considered as migratory; however, its route in India is still unknown. Hence, to find out its migration route genetic diversity, genetic structure and gene flow of 16 N. lugens populations from major rice growing regions of India was studied based on mitochondrial cytochrome oxidase I (COI). The results revealed a high genetic homogeneity among the populations on the basis of genetic diversity statistics and neutrality tests. There was a prevalence of a single major haplotype across the country. No spatial relevance was found with the genetic structure of the populations indicating presence of excessive gene flow among them. Extensive gene flow among populations was also confirmed with the presence of higher number of immigrants in North, Central, and East India. To further clarify the migration sources, 48 h air-mass reverse trajectory was performed for Varanasi just aftermath of cyclones Amphan and Yaas, which disclosed Eastern/Northeastern states along with Bangladesh and Myanmar as the possible source areas. Overall, the results revealed a single panmictic homogeneous population of N. lugens in India with extensive gene flow as a consequence of their migration. These findings will help in better forecasting enabling efficient regional management of this important rice pest. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-022-03337-6.