Abstract
BackgroundGenetically modified (GM) crops have become a common tool for managing insect pests of economic importance. However, before their commercialization, bio-safety evaluation on non-target arthropods such as pollinators and biological control agents is a pre-requisite to save services rendered by them in agro-ecosystem.ResultsIn the present experiment, the potential adverse effects of Bt protein (Vip3Aa) were studied on the life table parameters (pupation and emergence rates, 7-day larval weights, larval development time, and adult weight) of a predatory beetle, Propylea japonica (Thunberg) (Coleoptera: Coccinellidae) in the laboratory. P. japonica was exposed to Bt protein incorporated in synthetic diet at the rate of 200 µg/g of fresh weight of diet. Temporal stability, bioactivity and the uptake of insecticidal protein were confirmed by enzyme-linked immunosorbent assay and a sensitive insect bioassay. The results indicated that pupation and adult emergence rates did not differ significantly from that of negative control (pure synthetic diet). Similarly, the fresh weight of male and female adults emerged in Vip3Aa treatment (2.87 mg and 3.86 mg, respectively) did not vary significantly from that of the negative control treatment (2.66 mg, 3.75 mg). However, the time taken by the larvae to complete their development (12.70 days) was significantly extended than that of the negative control (10.21 days). In contrast, the tested life-table parameters of P. japonica were adversely affected when fed on synthetic diet containing boric acid (positive control) indicating experimental fitness to detect adverse effects.ConclusionsOn the basis of the results, it is suggested that GM crops expressing Bt protein (Vip3Aa) are safe for non-target insects such as P. japonica and are compatible with other biological programs for the integrated management of insect pests.
Highlights
Modified (GM) crops have become a common tool for managing insect pests of economic importance
Impact of Vip3Aa on the life table parameters of P. japonica The results indicated that about 57–60% larvae successfully completed their development and successfully pupated in the negative control and Vip3Aa treatments, which did not differ significantly (Fig. 1)
The time taken by the larvae to complete larval development was significantly prolonged in the Vip3Aa treatment than that of the negative control (Table 1)
Summary
Modified (GM) crops have become a common tool for managing insect pests of economic importance. Extensive use of insecticides increases resistance in insect pests and reduces the bio-diversity of non-target arthropods (NTA) (Jafar et al 2013). To overcome these problems, scientists have modified the crops genetically using the genes of Bacillus thuringiensis (Berliner) with the aim to provide enhanced resistance in plants against insect pests without affecting NTA. Bt secretes numerous vegetative insecticidal proteins (Vip) during its vegetative phase These proteins have shown a broad-spectrum activity against Lepidoptera without sharing target binding sites with Cry proteins in the target insect midgut.
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