Evolution of Resistance to Bacillus thuringiensis

TLDR

Bacillus thuringiensis insecticides are widely used for pest control, are highly toxic to target pests while sparing non‑target organisms, but rising environmental concerns and emerging field resistance threaten their long‑term efficacy. The study aims to enhance Bt’s utility through genetic innovations and to develop strategies that delay or reverse resistance in pest populations. Bt toxins are proteolytically activated in the insect midgut, bind to brush‑border membranes, and form pores that cause cell lysis. Recent field and laboratory evidence shows that resistance to Bt has emerged in major pests, making resistance evolution the greatest threat to Bt’s continued success.

Abstract

Insecticides derived from the common soil bacterium Bacillus thuringiensis (Bt) are becoming increasingly important for pest management. Insecticidal crystal proteins (also called 8-endotoxins) from Bt are extremely toxic to certain pests, yet cause little or no hann to humans, most beneficial insects, and other nontarget organisms (19, 40). After proteolytic activation in the insect midgut, Bt toxins bind to the brush border membrane of the midgut epithelium and create pores that cause cells to swell and lyse (55). Technical innovations, including expression of Bt toxin genes in transgenic crop plants and transgenic bacteria, should increase the usefulness of Bt (6, 12, 35, 46, 91, 94, 109, 116). At the same time, mounting concerns about environmental hazards and widespread resistance in pest populations are reducing the value of conventional synthetic insecticides. Because Bt had been used commercially for more than two decades without reports of substantial resistance development in open field popu­ lations, some scientists had presumed that evolution of resistance was unlikely (21, 89). However, resistance to Bt was documented recently in field populations of diamondback moth in Hawaii, the continental US, and Asia (36, 42, 92a, 128, 129, 131, 138, 146, 148, 151). These reports confirmed suspicions raised by the results of laboratory selection for resistance to Bt in several major pests (102, 104, 135). Scientists in industry, government, and academia now recognize evolution of resistance to Bt in pests as the greatest threat to the continued success of Bt (18, 44, 58, 59, lOla, 108). To delay or reverse resistance to Bt in pests, we must first understand