Responses of the cutworm Spodoptera litura (Lepidoptera: Noctuidae) to two Bt corn hybrids expressing Cry1Ab

Shu Yinghua,Wei Jiaxi,Chen Jin,Du Yan,Wang Jianwu

doi:10.1038/srep41577

Shu Yinghua, Wei Jiaxi + Show 3 more

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https://doi.org/10.1038/srep41577

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Journal: Scientific Reports	Publication Date: Feb 10, 2017
Citations: 22	License type: open-access

Affiliation: South China Agricultural University

Abstract

To examine the responses of the secondary lepidopteran pest Spodoptera litura to two Bacillus thuringiensis (Bt) corn hybrids [5422Bt1 (Event Bt11), 5422CBCL (MON810)] expressing Cry1Ab, larval bioassays with Cry1Ab toxin, corn leaves or kernels and bagging on corn plants were conducted. The results showed that larvae displayed a similar performance when fed kernels, but not leaves of 5422Bt1, 5422CBCL and their near-isogenic non-Bt corn (5422). Significantly higher Cry1Ab amounts were detected in larvae fed leaves than kernels of both Bt hybrids, with different molecular weights of protein band in plants (72 and 90 kDa for 5422Bt1 and 5422CBCL, respectively), gut contents (65 kDa), feces (50 kDa), which indicated that larvae had lower ingestion, higher degradation and excretion of Cry1Ab when fed kernels not leaves of both Bt hybrids. Significantly higher levels of cadherin-like receptors and alkaline phosphatase transcripts were detected in larvae fed leaves than kernels of two Bt hybrids. Catalase, superoxide dismutase and glutathione-S-transferase activities in larvae fed 5422Bt1 leaves were significantly higher than that of 5422 treatments. Therefore, S. litura had low susceptibility to 5422Bt1 and 5422CBCL when larvae fed kernels not leaves of Bt corn. Additionally, S. litura presented a much stronger tolerance to 5422CBCL than 5422Bt1.

Highlights

To examine the responses of the secondary lepidopteran pest Spodoptera litura to two Bacillus thuringiensis (Bt) corn hybrids [5422Bt1 (Event Bt11), 5422CBCL (MON810)] expressing Cry1Ab, larval bioassays with Cry1Ab toxin, corn leaves or kernels and bagging on corn plants were conducted
The approximate digestibility (AD) and efficiency of conversion of digested food (ECD) of S. litura larvae compared to the control showed significant differences in the following Cry1Ab concentrations treatments, 150 and 250 μgg−1 (Fig. 1C,E)
No significant differences between control and treatments were observed in relative consumption rate (RCR) and efficiency of conversion of ingested food (ECI) of S. litura (Fig. 1B,D)

Summary

Introduction

To examine the responses of the secondary lepidopteran pest Spodoptera litura to two Bacillus thuringiensis (Bt) corn hybrids [5422Bt1 (Event Bt11), 5422CBCL (MON810)] expressing Cry1Ab, larval bioassays with Cry1Ab toxin, corn leaves or kernels and bagging on corn plants were conducted. Higher levels of cadherin-like receptors and alkaline phosphatase transcripts were detected in larvae fed leaves than kernels of two Bt hybrids. S. litura had low susceptibility to 5422Bt1 and 5422CBCL when larvae fed kernels not leaves of Bt corn. Other studies have reported that M. unipuncta and Helicoverpa armigera could survive when they were fed Bt corn[6,7] These secondary lepidopteran pests may display low susceptibility or develop resistance to Bt corn and gradually evolve into key pests, which has raised many concerns recently[8,9,10]. The proteolytic activation of protoxins and subsequent binding of the active toxin to receptors have been characterized as two crucial steps in mode of Cry[1] action

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