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Effects of Bt Rice on Arthropod Community in Postharvest Seasons and Toxicology of Folsomia Candida (Collembola: Isotomidae)

Author: ZuoRuiHong
Tutor: BaiYaoYu
School: Southwestern University
Course: Biosafety
Keywords: transgenic Bt rice postharvest seasons arthropod community Folsomia Candida toxicology
CLC: S511
Type: Master's thesis
Year: 2010
Downloads: 109
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Abstract

The biosafety of transgenic plants has been becoming a focus in the world. Concerns of biosafety of transgenic Bt rice are very necessary, because rice is one of major foods of human. Unexpected effects were caused as a result of the insertion of genes, and Bt insecticidal protein could persist a long time with stems and leaves after Bt rice straw returning-to-field in the field. In this paper, laboratory and field studies were carried out by using transgenic Bt rice, KMD1 and KMD2, containing a synthetic crylAb from Bacillus thuringiensis under the conthol of maize ubiquitin promoter, which are japonica rice with their parental control cultivar Xiushui 11. Effects of Bt rice on aboveground arthropod community in postharvest seasons were researched. Meanwhile, effects of Bt rice on the toxicology of Folsomia candida, which is one representative of soil animals in the paddy fields, were studied. The results are as follows:Effects of straw returning-to-field of Bt rice on biodiversity of aboveground non-target arthropod community in postharvest seasons were studied in the paddy fields using litterbag traps and pitfall traps in 2008/2009 in Chongqing. A total 48872 arthropods, representing four functional guilds, detrtivores, phytophages, predators, and parasitoids, were captured using the two methods. The detrtivores was the predominant group, accounting for 92.9% of the total captures, followed by predators (4.1%), phytophages (2.7%) and parasitoids (0.3%). In the most case, the dominant group compositions of arthropod guilds were the same between Bt rice paddy habitats and their control. Both for Bt rice and the control, Entomobryidae and Sminthuridae. Aphidi, Carabidae and Lycosidae, and Figitidae were the dominators among detrtivores, phytophages, predators and parasitoids, respectively. There were no significant differences between Bt rice and the control of non-Bt paddy plots in the proportions of different groups in total captures, family composition and dominance. As to arthropod community indices such as species richness, Shannon-Wiener diversity index, evenness index, dominance index and their temporal dynamics in rice paddy habitat, there were no marked differences between Bt rice plots and the control. At the same time, most of the dissimilarities in different sub-communities from detritivore, phytophagou. predator. parasitoid. and arthropod communities as a whole between Bt rice plots and the control were apparently low.Effects of Bt rice on toxicology of F. candida were studied using both experimental systems under laboratory conditions. (1)Petri dishes:F. candida were maintained on a plaster of Paris/graphite substrate and were supplied with Bt rice leaves in order to constant monitoring troughout the exposure period. We discovered that Bt rice enterded into body of F. candida. The parameters such as body length、ecdysis rate, number of offspring and population growth rate performed equally well when reared on two Bt and non-Bt rice varieties. (2)Soil-litter microcosms for single species tests:Effects of different amounts of Bt rice leaves in soil on reproduction and population growth rate of F. candida were studied. At the end of 4-week exposure, there were no significant differences in reproduction and population growth rate of F. candida in all rice treatments. At the same time, SOD activities were determined at the end of two experimental systems, using the test kits offered by Nanjing Jiancheng Biological Engineering Institute, the results indicated that SOD activities in F. candida fed on Bt rice changed slightly compared with the control, which had no visible effect on the SOD activities.In general, straw returning-to-field of transgenic Bt rice has no significant impact on biodiversity of aboveground arthropod communities in postharvest seasons. There were no negative effects of Bt rice on growth and development, reproduction rate and SOD activities of F. candida. Further persistent studies are needed to clarify the effect of Bt rice on soil animals of paddy fields.

Effects of Bt Rice on Arthropod Community in Postharvest Seasons and Toxicology of Folsomia Candida (Collembola: Isotomidae)

Abstract

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