Stems of the rice plants showing symptoms of bakanae disease caused by Fusarium moniliforme were collected in the summer of 2004 in the paddy field at the China National Rice Research Institute (CNRRI), Hangzhou, China. They were cut into 3 cm pieces, sur face sterilized with 0.1% aqueous solution of mercuric chloride, rinsed twice with distilled water and then grown on potato dextrose agar medium. The plates were incubated at 30 ± 2°C for four days. The isolated fungus was identified according to Booth (1971) and Nelson et al. (1983). The spores of Fusarium moniliforme were washed with distilled water and filtrated through gauze. The concentration of the spores was measured with spectrophotometer at 560 nm according to the method of Ahmed et al. (1986) who indicated that the concentration was 1.50× 105/ml-1 when the transmittance was 6.65, and the conidia were inoculated according to the method of Ahmed et al. (1986) with a concentration of 1.50 ×105 ml-1 conidia. The rice seedlings were inoculated with the fungus spores and treated with GA3. In each replication, seeds of each genotype were firstly soaked for 36 hours in Carbendazim solution diluted in 5000 folds. Then they were washed and transferred to the growth chamber and germinated at 32oC. When the bud was about 0.5 cm in length, germinated seeds of each genotype were divided into three parts for different treatments: 10 germinated seeds were inoculated with spore of the fungi, 10 treated with GA3 (50 mg l-1) and the remaining 10 were treated with distilled water as control. After 24 hours of treatment at 32oC, the seedlings were washed with distilled water
and permitted to grow for 5 ∼ 7 days at 30oC until the two-leaf stage, then the length of the seedlings were measured.