Leaf surface factors of transgenic Bt cotton associated with the feeding behaviors of cotton aphids: A case study on non-target effects

Abstract

The present paper reports case study results of the risk assessment of transgenic Bt cotton on a non-target pest, cotton aphid, Aphis gossypii. Several types of techniques, i.e., electrical penetration graph (EPG), light and electron microscopy, bioassays and chemical analysis, were applied to investigate physical and chemical leaf factors of 2 transgenic Bt cotton lines (GK12 and GK19) and their parental non-Bt cotton line (Simian3) associated with searching and feeding behaviors of cotton aphids on leaves or leaf extracts of cotton plants. EPG results showed that there were some differences among behaviors of cotton aphids on 2 Bt cotton and 1 non-Bt cotton lines. Cotton aphids performed similarly to leaf surface extracts from 3 cotton lines; and leaf surface chemicals, mainly volatiles and waxes, were almost identical in the components and concentrations among the cotton lines. However, three cotton lines were quite different from each other in the densities of certain kinds of covering trichomes. Therefore, the relationships between the physical characteristics and the searching behaviors of cotton aphids on the three cotton lines were constructed as the regression equations. Glandular trichomes and covering trichomes with 5 branches influenced the cotton aphids' searching behaviors effectively; and other trichomes with other branches affected aphids in varying ways. These results demonstrated that leaf surface physical factors of transgenic Bt cotton lines different from their parental non-Bt line could affect the penetration behaviors of non-target cotton aphids. Cotton aphids penetrate and feed more easily on two Bt cotton lines than on the non-Bt cotton line.

Indian Bt Cotton Varieties Do Not Affect the Performance of Cotton Aphids

“…The latter effect was also found in our study. While a previous study reported differences in the trichome density between Bt and non- Bt cotton plants [33], this could not be confirmed for the three cotton varieties used in our study. It was noticeable, though, that the trichome density of Bt plants showed considerably less variation as compared to non- Bt plants.…”

Transgenic cry1C⁎ gene rough rice line T1C-19 does not change the host preferences of the non-target stored product pest, Rhyzopertha dominica (Fabricius) (Coleoptera: Bostrichidae), and its parasitoid wasp, Anisopteromalus calandrae (Howard) (Hymenoptera: Pteromalidae)

“…The densities of trichome and sclereid measurements at the surface of rough rice were carried out under a scanning electron microscope (SEM) (Tokyo, Japan) (Xue et al, 2008). Thirty samples were examined and the results were calculated as trichome and sclereid density per 1 mm 2 .…”

Intraspecies mixture exerted contrasting effects on nontarget arthropods ofBacillus thuringiensiscotton in northern China

“…The seeds of the two genotypes were provided by colleagues from the Biotechnology Research Center of CAAS. Cotton genotypes exhibited marked differences in leaf trichome density (Xue et al, 2008), Bt toxin content (Zhang et al, 2006) and associated resistance to lepidopteran species.…”

“…However, the effects of mixed-row intercropping showed a significant variation among years and within genotypes. Xue et al (2008) stated that the outbreak of cotton aphid was more frequently observed in transgenic Bt cotton because the lower leaf trichome density of transgenic Bt cotton facilitated aphid feeding compared with conventional non-Bt cultivars. Accordingly, we would have expected an intermediate cotton aphid population in mixture plots, with the highest densities in Bt plots and the lowest densities in non-Bt plots.…”