Modes of Action of Dwarfing Genes on Physiological and Biochemical Characters in Rice (Oryza sativa L.)

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Using a rice variety "Shiokari" and its dwarf near-isogenic lines, several experiments concerning the title of project above were carried out. The results obtained are as follows : (1) Degrees of response in shoot elongation to GA_3, inhibitors of gibberellin biosynthesis, IAA and its precursors differed among lines used. Amount of endogenous IAA extracted from shoots was fewer in Sh-d_1 and Sh-d_<18>^h than in "Shiokari". (2) Peroxidase activity in the upper two internodes of Sh-d_<13> and Sh-d_6 was remarkably high as compared with "Shiokari". Other dwarf lines also tended to show higher activity than "Shiokari". A negative correlation was observed between the peroxidase activity and the internode length especially in the second internode. (3) Lignin content was measured in the upper three internodes at various stages of growth. There was significantly negative correlation between the lignin content (%) measured at heading stage and the length of parenchyma cell measured at maturity stage. On the other hand, the lignin content (%) at maturity stage correlated positively to the internode length. (4) Random amplified polymorphic DNAs (RAPDs) were detected between "Shiokari" and three dwarf near-isogenic lines by amplification using 180 kinds of single 10-mer primers of arbitrary sequence. Among four RAPDs detected in three dwarf lines, one RAPD was subjected to investigate the segregation ratio in a F_2 population and was confirmed to segregate at a 3 : 1 ratio. A search of new RAPDs and a linkage analysis of dwarfing genes and RAPDs are now carrying aut.