Note that most seedlings of XHA and all seedlings of XHA-I, which carried the d1 gene were insensitive to both GA 3 and bakanae, but they died after transplanting. Observation under a microscope indicated that the seedlings were truly infected with Fusarium moniliforme. It is possible that the expression of d1 gene induced the lack of α -subunit of the heterotrimeric G-protein (Gα ) for GA signal transduction, thus retarded the transmission of GA3 (Ueguchi-Tanaka et al., 2000), and did not promote the elongation of seedlings.
2. The response of eui recessive and wild-type genotypes to GA3 and bakanae disease
 The response to GA 3 was significant (P < 0.05) in the semidwarf variety GC2 and highly significant (P < 0.01) in all the other genotypes (Table 2), whereas the response to bakanae disease varied greatly among different genotypes. The elongation promoted by the fungus inoculation was not significant in the wild-type tall-plant genotypes, but significant in the genotypes carrying sd1, and highly significant in the eui recessive tall-plant genotypes. Similar variations were observed in the seedling mortality after transplanting to the field. All the seedlings of the wild-type tall-plant genotypes grew normally, whereas the semidwarf genotypes and eui genotypes had high mortalities of 43.3∼60.0% and 73.3∼83.3%, respectively (Table 2). This indicated that all the six rice lines carrying sd1 were susceptible to bakanae disease, but the wild-type tall genotype was resistant.