Effect of the pollen of transgenic rice line, TT9-3 with a fused cry1Ab/cry1Ac gene from Bacillus thuringiensis Berliner on non-target domestic silkworm, Bombyx mori Linnaeus (Lepidoptera: Bombyxidae)

Abstract

Some cry genes from Bacillus thuringiensis Berliner (Bt) have been transferred into rice plants for resistance to lepidopterans. The ecological risks of Bt rice, especially the non-target effects of Bt rice pollen on the domestic silkworm, Bombyx mori Linnaeus in mulberry-rice mixed cropping area should be clarified cautiously. In light of B. mori fully domesticated and not surviving independently in the field, a series of laboratory bioassays were conducted to evaluate the effect of the pollen from an indica transgenic rice line, TT9-3 with a fused cry1Ab/cry1Ac gene on B. mori based on the investigation of rice pollen deposition under normal field conditions and the quantitation of the fused insecticidal protein expression in the pollen. No significant adverse effects were observed on the survival, growth and development of B. mori young larvae, even after the neonates had been exposed to Bt pollen at the highest density of 3,395.0 grains/cm 2 for 48 h which the pollen density is far higher than the highest pollen density on mulberry leaf, 1,635.9 grains/cm 2 , naturally occurred in the field. According to these results and considering the extensive biotic and non-biotic factors such as the type of Bt genes used and expressed in Bt rice line TT9-3 which are safe to B. mori, the relatively low exposure amount of insecticidal protein in the Bt pollen, and other conditions which influence the silkworm's exposure to Bt pollens, it suggests that the pollen from Bt rice line, TT9-3 poses little effect on silkworm rearing in natural settings.

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

“…The culture of the silkworm Bombyx mori is an important export industry that provides considerable income for people in many temperate Asian countries [22]. However, B. mori is susceptible to Cry1Ac and Cry2Ab proteins.…”

“…Existing results show that Bt toxins have no lethal effect on the two insects. Few studies of the sublethal effects of Bt toxins on A. mellifera [18], [20], [26], [27] and B. mori [22], [23], [28] have been conducted either. However, as well as the side effects of pesticides on beneficial arthropods [29]–[31], the sublethal effects of Bt toxins on these two economically important insects might negatively impact larval development and immune capacity and lead to colony population decrease [31].…”

Impacts on silkworm larvae midgut proteomics by transgenic Trichoderma strain and analysis of glutathione S-transferase sigma 2 gene essential for anti-stress response of silkworm larvae

“…It is also the representative non-target insect of pesticide [38,39]. Pesticide toxicology of silkworm is required for pesticide registration in China.…”

Opinion of the Scientific Panel on genetically modified organisms [GMO] related to the safeguard clause invoked by Greece according to Article 23 of Directive 2001/18/EC and to Article 18 of Directive 2002/53/EC

“…This measure would decrease the direct exposure of silkworms to maize pollen. In this respect, Yao et al (2006) conducted a series of laboratory bioassays to evaluate the effect of the pollen from a GM rice line with a fused cry1Ab/cry1Ac gene on silkworms. No significant adverse effects were observed on the survival, growth and development of silkworm young larvae, even after the neonates had been exposed to Bt pollen at the highest density of 3,395.0 grains/cm 2 for 48 h.…”

“…Yao et al (2006) concluded that Bt rice pollen pose little effect on silkworm rearing in natural settings. Taking into account the available literature data, the GMO Panel is of the opinion that the risk of MON810 pollen to silkworm and other non-target lepidopteran species is negligible due to its low CRY1Ab content and the low levels of exposure of wild species to maize pollen.…”