Areum Chun

Content and characteristics of resistant starch in high amylose mutant rice varieties derived from Ilpum.

This study was conducted to analyze the starch characteristics of three rice cultivars, Goami 2, Goami 3 and Goami 4 with high amylose content and resistant starch. These rice varieties were developed by mutation breeding based on N-methylN-nitrosourea (MNU) treatment in a japonica variety, Ilpum. Resistant starch contents of three high amylose mutant rice varieties and Ilpum were 11.87~13.69% and 0.36%, respectively. The X-ray diffraction patterns of starches of three varieties, Goami 2, Goami 3 and Goami 4 displayed B-type pattern. The proportion of amylopectin short chains of 6 to 12 in DP of the high amylose mutant rice varieties was significantly lower than that of Ilpum. Resistant starch contents had positive correlation with the amylose content, total dietary fiber content, medium length chains of 13 to 24, long chains of ≥ 25 in DP of amylopectin, pasting temperature and setback viscosity.

Identification of novel mutations in the rice starch branching enzyme I gene via TILLING by sequencing

Starch branching enzymes (SBEs) incorporate α-1,6-branched glucosidic linkages into α-1,4-glucan chains. Rice has three SBE isoforms (SBEI, SBEIIa, and SBEIIb), which differ in the amylose chain lengths that they transfer to amylopectin. SBEI mutants characterized to date have had little or no effect on starch structure or content. In this study, TILLING by sequencing was employed to identify SBEI mutations in a population of chemically induced mutants of the cultivar Nipponbare (n = 4096), resulting in the detection of 37 putative mutations. After removing mutations in introns or predicted to be synonymous, Sanger sequencing of M2 and M3 generation mutants confirmed six mutations and homozygous lines for four of these mutations were isolated. Only one line, NM-4936, exhibited a visible grain phenotype and produced sufficient M4 seeds for morphological and physicochemical analyses. In contrast to Nipponbare, NM-4936 grains are opaque due to rounded, loosely packed starch granules, and consequently, grain hardness was significantly reduced. NM-4936 grains exhibited significantly reduced width and thickness, which is reflected in reduced grain weight. Physicochemical analysis revealed significant differences in apparent amylose content (15 vs. 19%) and protein content (9.2 vs. 4.8%). Amylopectin chain-length distribution analysis indicated that the mutant has a slight but significant decrease in B3 chains [degree of polymerization (DP) ≥ 37, P < 0.01] and a very slight but significant increase in B1 chains (DP 13–24; P < 0.05). Identification of novel SBEI mutations will be useful in elucidating its function and may provide useful germplasm for breeding novel quality traits.

Quality Properties of Makgeolli Brewed with Fiber-rich Rice Cultivars

Goami2, Goami3 and Goami4 were identified as fiber-rich rice cultivars which were developed by mutation breeding with Ilpum. The purpose of this study was to develop a method for producing Makgeolli with the fiber-rich rice cultivars, Goami2, Goami3, Goami4, and to investigate the characteristics of Makgeolli during the fermentation process. Makgeolli was produced herein by fermentation steamed rice (SR), raw rice flour (RF), and steamed rice flour (SF) from Goami2, Goami3, Goami4, Ilpum and Sealgaeng rice cultivars. The physicochemical characteristics including alcohol and sugar content, pH, total acidity, TDF (total dietary fiber), and color of the Makgeolli samples were analyzed. Makgeolli produced with Ilpum and Sealgaeng showed satisfactory fermention characteristics in alcohol and sugar content when SR, RF and SF were used. In the case of Goami2, Goami3, and Goami4, the use of SF resulted in 17.2~20.1% alcohol content, whereas only 10% alcohol was produced by SR. The sugar contents in the SF-makgeolli samples were also higher (9~10 °Brix) than in the SR-makgeolli (5.35~5.44 °Brix) for Goami2 and Goami4 cultivars. The dietary fiber contents of the Makgeolli samples produced using SF from the fiber-rich rice cultivars were higher (1.35~1.52 g/100 mL) than those produced with Ilpum and Sealgaeng (0.74~0.87 g/100 mL). From these results, it may be suggested that SF would be an appropriate material to brew Makgeolli using fiber-rich rice cultivars to obtain better physicochemical and functional qualities.