基金Supported by the National Natural Science Foundation of China (30330390 and 30390083)the State Key Basic Research and Development Plan of China(2004CB117200)+2 种基金the Hi-Tech Re- search and Development(863) Program of China(2003AA207080)the Special Project for Adjusting Agricultural Production Structure from the Ministry of Agriculture of China(05-02-01A)the Knowledge Innovation Program of the Chinese Academy of Sciences(KSCX2-SW-304)