The Ecological Fitness Effect Of Transgenic Bt Cotton Under Different Habitats

The commercialization of GM plants has generated huge economic effects,but the accompanying ecological safety problem caused great concerns around the world.The fitness of GM plant is a central topic to evaluate GM plants' effects on ecological environment.In theory,plant' s new characters endowed by alien gene produce not only generate fitness profit but fitness cost as well.With the continuous expansion of the commercial scale of transgenic plants,the possibility that transgenic plants into the natural ecological system is is also growing.Nowadays,many studies about GM plant' s fitness under farmland conditions have been performed,but studies about GM plant's fitness under natural/semi-natural conditions are relatively few.Whether GM plants could survive and reproduce in natural environment and how the introduction of alien gene would affect plants' fitness are still need to be thoroughly studied.This dissertation chose cotton as material to study GM/non-GM cultivar's fitness and alien Bt gene ' s behavior under multiple environments in 2014 and 2015.Our experimental fields including farmland ecosystem,semi-farmland-semi-natural ecosystem and natural ecosystem.Among all four experimental fields,pingding was most close to typical farmland on soil condition and management so represented farmland ecosystem.Grassland field,which was covered by plenty weeds,had high organics but low minerals.Shrub field,with extremely low fertility and water content,and few weeds,was liable to soil erosion.Therefore,both grassland and shrub represented natural ecosystem and no labor management was applied.Hill field,with moderate fertility and weeds competition,was applied with a small amount of fertilizer before plantation but no more fertilizer was added and no labor management was applied.Therefore,hill field represented a semi-natural ecosystem.Since no cotton was planted in territory of several kilometers,no typical pest of cotton was observed,target and non-target insect pest pressure were lower.In this study,fitness parameters included height,branch number,above-ground biomass,seeds production.The alien gene's expression level relative to reference gene and the absolute amount of alien protein were measured to explore alien gene' s behavior.The results showed:in the same environment,GM cotton and non-GM cotton did not show significant differences on height,branch number and above-ground biomass.However,both GM and non-GM cotton showed significant differences on above-mentioned fitness parameters across multiple environments.In detail,fitness performance was best in farmland ecosystem and worse in semi-farmland-semi-natural ecosystem and worst in natural ecosystem,and different natural ecosystem also showed significant differences on height and branch number.On seeds production,Bt cotton and non-Bt cotton did not differentiate on farmland conditions while environments affected seeds production enormously,seeds production was very low,the vast majority cotton did not produce seed natural ecosystems.For transcription,Bt cotton showed a downward trend on Bt gene transcription with growth and along farmland to natural ecosystem gradient.Protein content was highest in farmland ecosystem and lower in semi-farmland-semi-natural ecosystem and lowest in natural ecosystem,but there is no uniform rise or downward trend with growth.Transcription levels of transgenic Bt cotton and protein expression levels were significantly correlated in farmland ecosystem but insignificant in another two ecosystems.In conclusion,fitness of transgenic cotton was significant affected by environments,but under environmental stress(such as low insect pest pressure,weed competition,low fertility and drought),transgenic cotton could not exhibit obvious fitness advantages compare with control.Moreover,alien Bt gene's expression behavior were also significantly influenced by environmental stress.