Effect of autosomally inherited, incompletely dominant, and unstable spinosad resistance on physiology of Tribolium castaneum (Coleoptera: Tenebrionidae): Realized heritability and cross-resistance

Abstract

The red flour beetle, Tribolium castaneum (Herbst) is one of the most destructive pests of stored commodities like cereals and grains in different tropical and sub tropic areas of the world. It causes qualitative and quantitative losses of stored products. Spinosad is recommended internationally to reduce pest infestations in storage structures. In this study, a population of T. castaneum collected from flour mills was selected with spinosad (Spin-Sel) and developed a resistant ratio of 122-fold after 12 generations. Spinosad resistance in Spin-Sel was unstable and decreased from 122 to 92-fold in the absence of selection pressure. Very low cross resistance to chlorpyrifos (8-fold), profenofos (3-fold), and cypermethrin (5-fold) in the Spin-Sel population as compared to the Unselected was observed. The toxicity data of heterozygotes revealed that spinosad resistance was autosomal and incompletely dominant. The realized heritability (h2) value was 0.07 for the first half selected generations and 0.17 for the latter half generations. The overall h2 value was 0.17. This study provides useful information that might clarify the nature of spinosad resistance in T. castaneum and help to formulate management strategies to delay the onset of resistance.