Impact of Single and Stacked Insect-Resistant Bt-Cotton on the Honey Bee and Silkworm

Lin Niu,Yan Ma,Lizhen Chen,Weihua Ma,Yao Zhao,Amani Mannakkara,Chaoliang Lei,Nicolas Desneux

doi:10.1371/journal.pone.0072988

Abstract

Transgenic insect-resistant cotton (Bt cotton) has been extensively planted in China, but its effects on non-targeted insect species such as the economically important honey bee (Apis mellifera) and silkworm (Bombyx mori) currently are unknown. In this study, pollen from two Bt cotton cultivars, one expressing Cry1Ac/EPSPS and the other expressing Cry1Ac/Cry2Ab, were used to evaluate the effects of Bt cotton on adult honey bees and silkworm larvae. Laboratory feeding studies showed no adverse effects on the survival, cumulative consumption, and total hemocyte count (THC) of A. mellifera fed with Bt pollen for 7 days. No effects on the survival or development of B. mori larvae were observed either. A marginally significant difference between Cry1Ac/Cry2Ab cotton and the conventional cotton on the THC of the 3rd day of 5th B. mori instar larvae was observed only at the two highest pollen densities (approximately 900 and 8000 grains/cm2), which are much higher than the pollen deposition that occurs under normal field conditions. The results of this study show that pollen of the tested Bt cotton varieties carried no lethal or sublethal risk for A. mellifera, and the risk for B. mori was negligible.

Highlights

China is one of the countries taking the lead in planting genetically modified (GM) crops, ranking sixth in the world by 2012 [1]
All Bt cotton cultivars were planted in the experimental field at Huazhong Agricultural University, Wuhan, China, and the University gave permission to conduct the study at this site
ELISA Results for Cry1Ac and Cry2Ab in Cotton Pollens The quantities of Cry1Ac or Cry2Ab in pollens of the two Bt cotton varieties were measured during the anthesis period from early bloom to late bloom

Summary

Introduction

China is one of the countries taking the lead in planting genetically modified (GM) crops, ranking sixth in the world by 2012 [1]. The planting area of transgenic Bt (Bacillus thuringiensis toxin) cotton reached 4.0 million hectares in China in 2012 [1]. Planting of Bt cotton cultivars has proven beneficial because of lower insecticide use and less damage from Helicoverpa armigera, the major pest of cotton [2,3]. An important technique in plant biotechnology is the stacking of resistance to multiple insects or of insect and herbicide resistance traits within a single cultivar [4]. The Bt toxins (Cry1Ac and Cry2Ab) target lepidopteran pests [7,8], and the EPSPS gene makes the plants tolerant to the herbicide glyphosate [9,10]

Objectives

Methods

Results