Plant height is one of the important agronomic traits of rice. Over higher plant would easily result in plant lodging and output reducing. On the other hand, the dwarf varieties with proper plant height had higher lodging resistance and a greater harvest index, allowing for the increased use of nitrogen fertilizer. Dwarf breeding had made a great breakthrough in the rice breeding. The breeding and extension of excellent dwarf varieties remarkably improved the yield potential of rice. Therefore, the plant height is still one of the focuses in rice genetic research.
So far a great deal of study has been made on the dwarf trait of rice, and about 60 dwarf and semidwarf genes have been reported (Kinoshita, 1984; Nagato and Yoshimura, 1998). More than 20 dwarf and semidwarf genes have been located on the rice chromosomes by using methods of classical genetics, and three semidwarf genes (Liang
et al, 1994; Maeda
et al, 1995; Jiang
et al, 2002) and nine dwarf genes (Kishimoto
et al, 1992; Yoshimura
et al, 1992; Yu
et al, 1992; Abenes
et al, 1994; Ideta
et al, 1994a; 1994b; Ashikari
et al, 1996) have been mapped by using molecular markers. Recently, two rice dwarf genes, d1 (Ashikari
et al, 1999 ) and d61 (Yamamuro
et al, 2000 ), have been cloned, which resulted in dwarf by acting on the signaling pathway of the endohormone. In the present study, a small grain dwarf mutant, designated as "162d", was identified from a semidwarf variety Shuhui 162, and the mutant gene was mapped with microsatellite markers. Meanwhile, the phenotype effects of the mutant gene were analyzed by using the near isogenic lines.
