The insecticidal efficacy and performance of Bt Cotton under variable abiotic stresses – A review on recent findings

Abstract

Bt cotton is a genetically modified crop that combats cotton pests (bollworm) by its insecticidal properties induced by insertion of endotoxin Cry1Ac gene from soil dwelling bacterium Bacillus thuringiensis. Bt cotton has been a big agricultural hit product of biotechnology for past 2 decades. Many countries have been successfully cultivating Bt crops on commercial scales. Transgenic Bt crops have favorably increased crop yields and solved global crisis of food shortage. Bt cotton crop shows variable insect resistance levels under the influence of multiple environmental abiotic stresses like high temperature, soil salinity, water logging and water deficiency, nitrogen deficiency, and humidity. These factors have been observed to degrade endotoxin protein content of transgenic crop and ultimately reduce its insecticidal efficacy. Under harsh environmental conditions, plant undergoes disturbed nitrogen metabolism and physiological mechanism distress. This review has discussed some of the major stress factors of Bt cotton and the underlying mechanisms of its unstable insecticidal efficacy under individual and combined stresses. Gene silencing, post transcriptional changes, protein degradation are some crucial reasons discussed in this review, but nitrogen metabolism is the most important research needed area of this domain. A detailed meta-analysis table has been drawn as a summary of various vital researches done in order to investigate the stress impacts. A deep research approach is needed to further elaborate the metabolic and physiological changes that take place in transgenic cotton crop under harsh stress states. Due to insufficient evidences and lack of solution strategies against this problem, there is a need of further research data to address this unstable protection of Bt crops against insects in order to enhance the ability and performance of the cotton crop worldwide.