Date Published: July 28, 2017
Publisher: Public Library of Science
Author(s): Qianjin Wang, Naishun Han, Cong Dang, Zengbin Lu, Fang Wang, Hongwei Yao, Yufa Peng, David Stanley, Gongyin Ye, Nicolas Desneux.
The advent of genetically modified (GM) Bt rice creates the possibility of interactions among Bt crops, crop pathogens and non-target herbivores. In particular, information on how pathogen-infected Bt-expressing plants will influence non-target herbivores is necessary to predict the sustainability of GM cropping systems. Laboratory bioassays were conducted to evaluate the potential combined impacts of rice dwarf virus (RDV) and two Bt rice lines, T1C-19 (Cry1C) and T2A-1 (Cry2A), on non-target green rice leafhopper (GRLH), Nephotettix cincticeps (Uhler) (Hemiptera: Cicadellidae). In the first experiment, GRLHs feeding preference tests on Bt rice lines compared to a parental control rice line, MH63, were conducted. As rice plants were uninfected with RDV, GRLHs generally preferred the control MH63 line over the two Bt lines during the initial 8 h, with no significant preference during the following 64 h. As rice plants were infected with RDV, there were no clear preferences between the Bt rice lines and the control MH63 line. In the second experiment, we assessed the combined influence of RDV-infection status and Bt rice lines on GRLH biological parameters. Egg duration, adult weights, and male adult longevity were significantly affected on RDV-infected Bt rice. Other parameters, egg hatching rate, nymph survival and fecundity were not significantly influenced. We infer that interaction effect among two testing Bt rice lines and RDV will not lead to enlarged pest populations, thus demonstrating that growing these two Bt rice lines will poses negligible risk to GRLH in sustainable rice agroecosystems. Long-term field experiments to monitor the population dynamics of GRLHs at large scale need to be carried out to confirm the current results.
Numerous genetically modified (GM) rice lines expressing insecticidal proteins from Bacillus thuringiensis (Bt) Berliner have been developed to control lepidopteran pest species [1– 3]. Two Bt rice lines, Huahui 1 and Shanyou 63, both expressing a fused insecticidal protein, Cry1Ab/Cry1Ac, were issued biosafety certificates in 2009 (renewed in 2014) for research into their commercial production in China . However, these two lines have not been approved for commercial production because further and continued assessment of their influence on agroecological and food security risks is necessary.
Our feeding preference study indicated that the GRLHs did not express feeding preferences among the rice lines. First, among three uninfected plants, GRLHs generally preferred the control MH63 line over the two Bt lines during the first 8 h post-inoculation, with no significant preference during the following 64 h. Second, among three RDV-infected plants, we recorded no clear preferences between the Bt rice lines and their parental control MH63 line. With regard to the GRLH rice plant preferences, one study reported that T2A rice did not influence host preference of a target pest, the leaffolder, Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) . Similarly, the T1C-19 rice did not alter the host preferences of the non-target stored product pest, Rhyzopertha dominica (F.) (Coleoptera: Bostrychidae), its parasitoid wasp, Anisopteromalus calandrae (Howard) (Hymenoptera, Pteromalidae) , or the host-searching behavior of another parasitoid, Cotesia chilonis (Matsumura) (Hymenoptera: Braconidae) . These findings make sense as T2A-1 and T1C-19 rice had volatile profiles similar to their non-Bt controls [33– 35]. These analyses also help to understand why the GRLHs in this study did not express feeding preferences among the rice lines.