Expression of Bt toxin in transgenic Bt cotton and its transmission through pests Helicoverpa armigera and Aphis gossypii to natural enemy Propylaea japonica in cotton plots

Abstract

The expression of Cry1Ac or Cry1Ab toxin in transgenic Bt cotton lines (NUCOTN 33B and GK-12) was detected; its transmission to the target pest insect, cotton bollworm Helicoverpa armigera (Hubner), the non-target pest, cotton aphis Aphis gossypii Glover, and the ladybird Propylaea japonica (Thunberg) was measured; and its effects on the ladybird were evaluated with the traditional cotton line, Simian 3 (the isogenic non-transformed line of GK-12) as the control, in cotton plots in Nanpi, Hebei, in 2002. The amounts of expressed Bt toxin in organs of transgenic Bt cotton NUCOTN 33B were higher (79.7-1 390.0 ng/g fresh weight) than those in GK-12 (16.5-264.0 ng/g fresh weight). During the blooming period of NUCOTN 33B plants, the order of Bt toxin content was as follows: stigma, anther ovary, petal grouped tender tip; the Bt toxin concentrations were similar as well as equal to those in grouped tender tip, when the newly development tender leaf of 5-7 leaf stage, the young square of early squaring period and the young boll of blooming period of NUCOTN 33B plants were tested. And during the blooming period of GK-12 plants, the order of Bt toxin concentration was as follows: anther stigma petal grouped tender tip ovary; the Bt toxin concentrations were similar and equal to those in grouped tender tip, when the newly development tender leaf of 5-7 leaf stage, the young square of early squaring period and the young boll of blooming period of GK-12 plants were detected. Moreover, the detection of trace amounts of Bt toxin in young boll, anther, stigma and ovary of the control cotton line, Simian 3, might be related to pollinators. In GK-12 and NUCOTN 33B cotton plots, Bt toxin could be transmitted to cotton aphis and cotton bollworm elder larvae. In the body of P. japonica larvae and adults, trace amounts of Bt toxin were detected only in those collected from NUCOTN 33B cotton plot. In addition, when P. japonica fed on cotton aphis collected from the transgenic Bt cotton plots, the development and survival from hatching to emerging as well as the reproductive ability of the ladybird were not significantly different with those of the control.