New Mutants of Specialty Rice Induced from Ilpumbyeo, a High-Quality Rice Cultivar, by MNU(N-Methyl-N-Nitrosourea) Treatment on Fertilized Egg Cells

Various mutants of specialty rice were derived from Ilpumbyeo, a high-quality japonica rice cultivar, through mutation breeding by MNU treatment on fertilized egg cells of rice spikelets. The selected mutants revealed glutinous, semi-glutinous (dull), opaque, floury, sugary, shrunken, chalky, clear transparent endosperm, and giant embryo characteristics. The majority of them were glutinous or dull and chalky endosperm. The amylose content of semi-glutinous dull mutants ranged from 6.0 to 13.0%. The specialty rice varieties induced from Ilpumbyeo by the chemical mutagen were a high-yielding glutinous rice ‘Suweon 428’, a semiglutinous rice ‘Baegjinju’, an opaque non-glutinous rice ‘Seolgaeng’, a high-amylose and fiber-rich rice ‘Goami 2’, and a giant-embryo rice ‘Keunnun’. They showed accompanying mutation effects of about one-week earliness on heading time and 8 cm longer length on culm in Suweon 428, and that of lower performance on the ratio of ripened grains and grain yield in ‘Goami 2’ and Keunnun as compared with Ilpumbyeo, the original cultivar. The alkali digestion value (ADV) of Baegjinju resembled to the glutinous mutant Suweon 428 showing slightly lower ADV than that of Ilpumbyeo. The ADV of Goami 2 was of similar level to that of Ilpumbyeo, but it revealed quite different pattern of ‘swelling’ in stead of ‘spreading’ pattern of the original cultivar. The amylose content was markedly lower in Baegjinju by about 50%, but was much higher in Goami 2 by about 50% compared to the original level of Ilpumbyeo, respectively. Goami 2 showed quite different morphological and structural characteristics of endosperm cell or compound starch granules from that of the original variety. Most of the endosperm cells of Seolgaeng were also packed with round-shape compound starch granules. The opaque endosperm of Seolgaeng may be useful for fermented food processing such as saccharized beverage or rice wine because of a lot of air space in endosperm. The giant-embryo rice, Keunnun produced about 2~3 times higher content of γ-aminobutyric acid by soaking in water as compared with the original variety.