Simulation On The Maize Pollen Dispersal Based On The Random-walk Model

Corn plays an important role in production as one of the main food crops as the world and our country. Earlier breeding methods, although cultivating a number of excellent varieties, had many disadvantages which could not be break though. From the 1980s, the transgenic technology that developed rapidly provided a new way for breeding and the industrial scale of the transgenic maize had reached the world’s second. At the same time, the impact, which the exogenous gene in transgenic crops transferred to other varieties or the closed related species by pollen dispersal, for the diversity of varieties or species and the ecological balance of nature appeared gradually. The main purpose of this study is to reveal the law of maize pollen dispersal through the application of the Lagrange Random Walk model which based on the simulation of maize pollen dispersal in large climatic background. Identify the parameters associated with the model through statistical analysis of the test results and revise the model in order to improve the accuracy. Based on the simulation of the model, the safety and isolating distance at different thresholds will be set and the impact of transgenic crops to the local ecology will be weakened. It will provide a scientific and reliable tool for further assessment of environmental security of transgenic crops.On basis of the data obtained from Nanjing and Gongzhuling experiments, we got the following conclusions after simulated the test results using different models:(1)Maize flowering time continued 8-10 days and the pollen dispersal peak period appeared in the first 2-6 days after flower, while the maxima is at the 2-4 days. The flowering peak in hourly flowering rate appeared before 11 am while the maximum is at 07-08 am. The optimum temperature range of maize flowering is 22-26℃ in the relationship between maize flowering and meteorological factors, while the maximum appeared at 24℃. The optimum relative humidity range is 65%-85%, while the maximum appeared at 75%. It is same substantially with previous research findings The optimum solar radiation intensity range is 100-400W/m2 in the morning while the maximum appeared at 250W/m2. In the afternoon, even solar radiation intensity weakened and temperature decreased, the hourly flowering rate affected by the low relative humidity was still very low.(2) The effect of the normal distribution model was not good in simulation to the maize pollen. The empirical model showed good agreement both in the daily pollen emission change in trend or in the extreme value on the size and time of occurrence. The effect of the normal distribution model had improved after making revisions to temperature and relative humidity. For three models of the hourly flowering rate, the models of Poisson and normal distribution were similar to the results for extreme values, while the model of Weibull was larger. All models were close to zero in the latter, less than the actual observations. Besides, in order to improve the model accuracy it still needs to obtain the relevant technical parameters of the model by the method of collection of samples.(3) The random walk model could simulate the changes in concentration of maize pollen in the pre-close position which downwind of the main wind direction, but it is unstable to no pollen area and the trend of pollen spread outward under different weather conditions. The simulation results was larger under calm wind or breeze in the weak pressure field conditions, while the simulation results were better in the strong wind, but it still had a certain gap between the actual results. The correlation between the concentration of pollen and the rate of gene flow was good. The model of gene drift rate which based on foregoing conclusions could not only simulate the gene flow rate of Gongzhuling trials, the effect of test for Lishui experiment was also better.