The Wx gene expression plays a major role in determining the amylose content in the rice endosperm, although Wx alleles and their trans-acting genes like du genes are also known to genetically control the amylose content. Experiments were conducted to determine whether genes inhibiting the Wx expression respond similary to two Wx alleles, Wx^-a and Wx^b, which are predominantly distributed in cultivated. A recessive mutant with chalky endosperm and showing an independent inheritance of wx was used in this study. Complementation tests showed that the mutant gene was allelic to du2 but the gene was designated as du2-2 as its phenotype was distinct. Nearisogenic lines (NILs) with different combinations of alleles at the Wx and du2-2 loci were then established and evaluated for the Wx gene expression. Waxy or chalky endosperms due to du2-2 were detected only in response to Wx^b but not to Wx^a, which may account for the fact that no du variants were detected in the Indica type. The potential use of du2-2 for improving the grain quality of the Indica type was discussed.