The Fitness Effect Of Transgenic Plants Under The Pressure Of Muti-factor Selection In Field Tests

The ecological safety of transgenic plants was concerned by people for a long time. The ability of transmission and durability of the foreign genes were decided by the fitness changes brought themselves.This article studied the fitness effects of5transgenic lines and their control from cotton and rice under different pest pressure, competition and metal stress. The experiments are carried out in both lab and field.The field experiments were implemented in two years. We chose two homozygous insect-resistant transgenic cottons as research object to test their difference to their controls under two different pest pressure and two different competition models. Fitness effects of the Bt and Bt/CpTI genes were examined in growth, anti-oxidase enzyme system, mass accumulation, photosynthesis and breed. In the process of field experiment, fitness costs were tested under low pest pressure and fitness benefits were tested under high pest pressure.The results of the field experiments of transgenic cotton showed, the plant height of transgenic cottons was significant lower than that of their respective control plants in many designs. The activities of antioxidant enzymes of transgenic cottons were higher than the non-transgenic contrasts. Especially the APX activity of transgenic cotton was significant higher than the respective control plants. The content of material accumulations of the transgenic cotton is lower. Most of the physiological responses mentioned above can be stronger when there were low pest pressure and strong competition existed. The mass of chlorophyll, net photosynthesis rate, seed and reproduction of transgenic cotton are lower than the non-transgenic control under low pest pressure.Three transgenic rice lines which transferred in Bt gene, CpTI gene and Bt/CpTI gene and their common non-transgenic control line were used in the lab experiment. Rice seedling were water planted under constant temperature and illumination. The responses of growth, mass accumulation and anti-oxidase enzyme system under5different levels of cadmium stress were tested to find the differences among these gene-types.The results of Cd stress experiment showed, non-transgenic rice line had the highest growth and photosynthesis level while there was no Cd stress. However, the responses of anti-oxidase system of transgenic rice lines are stronger than the one of non-transgenic line. So the transgenic lines can resist oxidation more effectively.In conclusion, the fitness effect of transgenic plant is related to the pest pressure, competition model, contaminant pressure and the type of foreign genes. The foreign genes can bring pressure to the physiological activities of the receptor and show fitness costs. Compare to the non-transgenic lines, transgenic plants have some fitness cost, but also have stronger adaptation when face Cd pressure.