Linkage analysis between gene for grain shattering and semi-dwarfing gene and character expression of shattering in rice

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The development of semi-dwarf rice cultivars has brought about a breakthrough in yield potential of yield in many rice growing countries of the world. It has become apparent that most semi-dwarf rice cultivars in the tropical and temperate regions carry the semi-dwarfing gene at the same locus As the Dee-geo-woo-gen gene sd-1.The linkage analysis between the semi-dwarfism and the shattering habit in both indica semidwarf cultivar Taicuiig Native 1 and japonica semi-dwarf cultivar Shiranui were carried out. The japonica tall cultivar Norin 29 and the two near-isogenic lines SC2 and SC4 were used in this study. SC2 and SC4 have both semi-dwarfing gene sd-1 and shattering gene derived from Taichung Native 1 and Shiranui, respectively. The degree of shattering was measured by an, apparatus for measuring the breaking tensile strength of the base of sterile lemma. The segregation patterns of shattering habit in the F_2s of SC2/Norin 29 and SC4/Norin 29 showed fit to a 3 non-shattering : 1 shattering genetic ratio, indicating that both SC2 and SC4 carry a single recessive gene controlling shattering habit, respectively. The F_1 and F_2 of SC2/SC4 showed the same shattering habit as that of both parents. Therefore, both SC2 and SC4 were considered to have the same shattering gene. The linkage relationship between the semi-dwarfing gene and the shattering gene was observed in the F_2s of SC2/Norin 29 and SC4/Norin 29. The weighted average of the recombination values estimated from the two-crosses was 13.1 %. A Chinese semi-dwarf cultivar was also proved to have the sd-l and the shattering gene linked to the sd-l in the 1st chromosome. From these result, it is assumed that the shattering gene has been transmitted to many semi-dwarf cultivars together with the sd-l in the breeding programs of semi-dwarf high-yielding cultivars. This shattering gene was symbolized sh-2.The abscission layer at the base of sterile lemma was observed before heading time.