Abstract:

【Objective】 Lethal and sub-lethal effects of transgenic rice containing cry1Ac and CpTI genes on the pink stem borer(Sesamia inferens) were studied to collect information for ecological risk assessment on insect-resistance to transgenic rice.【Method】 In vitro insect-feeding bioassay was conducted to evaluate the lethal and sub-lethal effects of transgenic rice lines (ⅡYouKF6 and KF6) on S. inferens at four different growing stages, i.e., seedling, tillering and elongation, booting, milk and maturing.【Result】Transgenic rice at seedling stage showed significantly high lethal effect on S. inferens with the shortest lethal duration of 50% and 100% of individuals and the highest corrected mortalities after feeding on transgenic lines at this stage for 3 and 6 days. Secondly followed by tillering and elongation stage, 50% and 100% of S. inferens were dead after feeding on transgenic lines at this stage for 4 and 10 days, respectively. Moreover, corrected mortalities for 6 days feeding on transgenic lines at this stage were significantly higher than that at booting and milk and maturing stages. Lethal effect of KF6 on S. inferens decreased significantly at booting stage. Lethal duration of 50% of S. inferens significantly extended and its corrected mortalities for 6 days feeding also declined remarkably. However, lethal effect of ⅡYouKF6 on S. inferens did not decrease significantly at this stage. Transgenic rice at booting and milk and maturing stages did not present significantly lethal to S. inferens and it showed the longest lethal duration of 50% of individuals and the lowest corrected mortalities for 3 and 6 days feeding. A few larvae of S. inferens could survive, pupate and emerged on these two transgenic lines at boot and milk and maturing stages. Sub-lethal effect of two transgenic lines on S. inferens also differed significantly between different developmental stages. Continuously feeding on transgenic rice lines at seedling and tillering and elongation stages could delay the development of larvae and pupae and decrease pupation rate, but no effect was shown on eclosion rate. Larval development was significantly inhibited after feeding on transgenic rice at booting stage, but no obvious effects were observed in pupal stages, pupation and eclosion rates. There were no significant differences for larval and pupal development, pupation and eclosion rates between feeding on transgenic and control rice lines at milk and maturing stages. Larval and pupal weights significantly declined, but no influence was shown on fecundity, when S. inferens infested on transgenic rice at any stage. 【Conclusion】 There were significant differences in lethal and sub-lethal effects of transgenic rice on S. inferens at different developmental stages, and the effects gradually decreased with the increase of growing stages of rice plant.

Key words: transgenic rice, Sesamia inferens, lethal and sub-lethal effect