Elevated CO2 not increased temperature has specific effects on soil nematode community either with planting of transgenic Bt rice or non-Bt rice.

Yingying Song,Jiawen Liu,Fajun Chen

doi:10.7717/peerj.8547

Abstract

BackgroundTransgenic Bt rice has not been approved for commercial cultivation because of the fierce public debate on food safety, biosafety regulation and ecological risk. Meanwhile, the concentration of CO2 and temperature in the atmosphere, as important environmental factors affecting the persistence of exogenous Bt protein, have increased. Elevated CO2, increased temperature, the planting of transgenic Bt rice and their interactions may further influence the structure and complexity of soil food web. However, the effects of transgenic Bt rice planting on soil organism remain largely unexplored before its commercial production especially under global climate change.MethodsHere, we assessed the influences of transgenic Bt rice (cv. HH with fused Cry1Ab/Cry1Ac in contrast to its parental line of non-Bt rice cv. MH63) on soil nematode communities under the conditions of elevated CO2 concentration and increased temperature for 2 years of 2016 and 2017 in open-top chambers located in Ningjin County, Shandong Province of China.ResultsElevated CO2 concentration remarkably increased the abundance of fungivores and significantly decreased their nematode channel ratio (NCR) and enrichment index (EI) irrespective of rice variety (transgenic Bt rice or non-Bt rice) or temperature (normal temperature or increased temperature). Additionally, rice variety and temperature did not significantly change soil nematode composition, abundance and ecological indices (including total maturity index (∑MI), Shannon diversity (H′), structure index (SI), NCR and EI). However, apparent seasonal changes were observed in theses aforementioned variables.DiscussionThese results suggested that atmospheric CO2 concentration but not temperature or rice variety has great impacts on soil nematode community, especially fungivores.

Highlights

Transgenic Bt rice is genetically modified with the exogenetic gene of Bacillus thuringiensis (Bt ) bacterium that codes for insecticidal proteins, and it has been used to improve crop yields and reduce the application of conventional insecticides (Chen, Shelton & Ye, 2011b)
Three blocks were used for CO2 and temperature treatments and each block was split into four OTCs, i.e., one with ambient CO2 concentration and increased temperature (A+T), one with ambient CO2 concentration and normal temperature (A-T), one with elevated CO2 concentration and increased temperature (E+T), and one with elevated CO2 concentration and normal temperature (E-T)
We found that there were no significant differences between rice variety on nematode community composition under elevated CO2 concentration or elevated temperature condition, which lead us to support the hypothesis (ii)

Summary

Introduction

Transgenic Bt rice is genetically modified with the exogenetic gene of Bacillus thuringiensis (Bt ) bacterium that codes for insecticidal proteins, and it has been used to improve crop yields and reduce the application of conventional insecticides (Chen, Shelton & Ye, 2011b). Elevated CO2 not increased temperature has specific effects on soil nematode community either with planting of transgenic Bt rice or non-Bt rice. Bt rice lines of Huahui-1 (HH) and Bt Shanyou 63 (Bt- SY63) both expressing fused Cry1Ab/Cry1Ac proteins in 2009 (Jia, 2010) and 2014 (Li et al, 2016), while they have not yet been approved for commercial cultivation because of the fierce public debate on food safety, biosafety regulation and ecological risk (Mendelsohn et al, 2003). Elevated CO2, increased temperature, the planting of transgenic Bt rice and their interactions may further influence the structure and complexity of soil food web. These results suggested that atmospheric CO2 concentration but not temperature or rice variety has great impacts on soil nematode community, especially fungivores

Methods

Results

Discussion

Conclusion