GURLAL SINGH*, SALIL KUMAR DWIVEDI AND RAVINDER NATH
Department of Entomology, School of Agriculture, Lovely Professional University, Jalandhar-144 001 (Punjab), India
*(e-mail : gurlalbrarr@gmail.com; Mobile : 82193-32861)
ABSTRACT
Bacillus thuringiensis (Bt), transgenic crops have done wonders in the field of plant protection since they were first introduced in 1996 in USA. Due to their economic benefit and environment-friendly nature, Bt crops were later adopted by countries like China and India. The genetically modified crops produced Cry toxin derived from Bacillus thuringiensis which kills insect-pest populations having alkaline pH in their midgut i. e. lepidopterans. However, over the years, various studies provided evidence of development of field evolved resistance in major insects of these crops. Eleven major lepidopteran insect- pests were reported to be found resistant to Bt crops up to 2011 and numbers are growing till date. This is a serious threat to the success streak of Bt crops in the long run. In most studies, the mechanism of resistance has been reported as mutation of Cadherin (binding protein of Cry toxin) in insect gut. Some other studies on Trichoplusia ni suggest that the resistance to Cry toxin is evolved by alteration of midgut amino-peptidase APN1& APN6 present on the epithelial membrane, by a trans-regulatory mechanism, which is down-regulation of APN1(which binds with Cry1Ac toxin) and up-regulation of APN6 (which does not bind with Cry1Ac toxins). In this review, some light is shed upon these mechanisms of Bt resistance briefly for better understanding of this problem as well as appropriate management techniques and strategies for delay of Bt resistance are also displayed like refuges, pyramid crops and sterile insects.
Key words : Bt crops, cry toxin, field evolved resistance, mechanism, management techniques