NEW LINES HARBORING DU GENES FOR LOW AMYLOSE CONTENT IN ENDOSPERM STARCH OF RICE

Two lines of rice, Tankei 1915 and 2019 with a low amylose content wer e registered as breeding materials in 1992. These lines were selected in the progeny following the treatment of the Japanese rice cultivars, Kinmaze and Kochihibiki with methyl-nitroso-urea (MNU). Tankei 1915 w as characterized by a dull endosperm which could be distinguished from waxy and non-waxy endosperms. The amylose content of Tankei 1915 was 9.2%, half of the content of the parental cultivar, Kinmaze. The line harbors the du-1 gene which is responsible for lowering the amylose co ntent and is located at a locus independent of the waxy (wx) locus on Chromosome 6. The other line, Tankei 2019, was characterized by a dull endosperm which is visually similar to the waxy endosperm. The amylos e content of Tankei 2019 was 6.3%, one-third of the content of the par ental cultivar, Kochihibiki. This line harbors the du-2 gene which is responsible for the decrease of the amylose content and is located at a locus independent of the wx and du-1 loci. The new type of endosperm starch of rice grains may contribute to the improvement of the eating quality of cooked rice and the development of new products in the foo d industry.