Supported in part by grants from the National Natural Science Foundation of China(NSFC)(30300238,30571193);Natural science Foundation of Jiangsu province(BK2004418);Hi-Tech Key project of Jiangsu province(BG2005314);Shanghai Agricultural Committee of China(2004-NO.9-1);key project of National Key Laboratory of Crop Genetics and Germplasm Enhancement(ZW2004-12)