High-quality Japonica Research Articles

Improvement of Flowering Stage in Japonica Rice Variety Jiahe212 by Using CRISPR/Cas9 System.

The flowering period of rice significantly impacts variety adaptability and yield formation. Properly shortening the reproductive period of rice varieties can expand their ecological range without significant yield reduction. Targeted genome editing, like CRISPR/Cas9, is an ideal tool to fine-tune rice growth stages and boost yield synergistically. In this study, we developed a CRISPR/Cas9-mediated multiplex genome-editing vector containing five genes related to three traits, Hd2, Ghd7, and DTH8 (flowering-stage genes), along with the recessive rice blast resistance gene Pi21 and the aromatic gene BADH2. This vector was introduced into the high-quality japonica rice variety in Zhejiang province, Jiahe212 (JH212), resulting in 34 T0 plants with various effective mutations. Among the 17 mutant T1 lines, several displayed diverse flowering dates, but most exhibited undesirable agronomic traits. Notably, three homozygous mutant lines (JH-C15, JH-C18, and JH-C31) showed slightly earlier flowering dates without significant differences in yield-related traits compared to JH212. Through special Hyg and Cas marker selection of T2 plants, we identified seven, six, and two fragrant glutinous plants devoid of transgenic components. These single plants will serve as sib lines of JH212 and potential resources for breeding applications, including maintenance lines for indica-japonica interspecific three-line hybrid rice. In summary, our research lays the foundation for the creation of short-growth-period CMS (cytoplasmic male sterility, CMS) lines, and also provides materials and a theoretical basis for indica-japonica interspecific hybrid rice breeding with wider adaptability.

Detecting QTL for internode length in rice to improve lodging resistance of high-quality japonica cultivar

Detecting QTL for internode length in rice to improve lodging resistance of high-quality japonica cultivar

Physicochemical Properties and Fine Structure of Starch in Jinong Xiangruan 1 and DGR1 Soft Rice Varieties Cultivated in Different Regions of China

Rice, a staple food for billions around the globe, is cultivated in numerous forms. Among them, soft rice is well known, which is characterized by its tender, creamy consistency and desirable texture. In this study, we examined the physicochemical properties and fine structure of starch from two soft rice varieties, Jinong Xiangruan 1 and DGR1, cultivated in different regions in China (Baodi District, Tianjin City; Liaoning Province; and Fengyang City, Anhui Province). The aim was to understand how amylopectin content (AC) influences rice quality. This research aims to bridge the knowledge gap regarding the role of amylopectin in determining rice’s adhesive consistency and viscosity. Significant regional differences were observed in yield components such as the number of grains per panicle, seed setting rates and 1000-grain weight, with Liaoning generally showing higher performance metrics compared to other regions. Physicochemical analysis highlighted that though glue consistency and taste values showed little regional variation, AC significantly influenced rice hardness and viscosity. Rapid Visco Analyzer (RVA) profile analysis further demonstrated distinct differences in viscosity characteristics, underscoring the regional impacts on starch behavior. Additionally, molecular weight distribution and amylopectin chain length analysis, conducted via SEC-MALLS-RI and ICS ion chromatography, revealed notable differences in starch composition across varieties and locations. The findings suggest that environmental conditions play a crucial role in defining starch characteristics and, consequently, the eating quality of rice. This provides valuable insights for breeding high-quality japonica rice with broad adaptability.

Construction of yield loss indicators for cold vortex, light-temperature-water combined stress during the flowering period of rice in Northeast China.

The construction of a yield loss evaluation index for the cold vortex type light-temperature-water composite adversity during rice flowering period in Northeast China is important for elucidating the impacts of cold vortex type composite disasters on rice yield loss in middle and high latitude areas. Moreover, it can provide meteorological support to ensure safe production of high-quality japonica rice in China and contribute to regional disaster reduction and efficiency improvement. By combining growth period data, meteorological data, and yield data, we delineated and constructed the composite stress occurrence index of cold vortex type light-temperature-water at the flowering stage of japonica. We analyzed the relationship between factors causing disasters and yield structure, as well as the relationship between different yield structures and yield by employing BP neural network method. We further dissected the processes involved in the causation of combined disasters. Based on the K-means clustering method and historical typical disaster years, we quantified the critical thresholds and disaster grades, and established an evaluation index and model for assessing yield loss caused by combined stress from cold vortex type light-temperature-water. Finally, we examined the spatial and temporal variations of low temperature, abundant rainfall, and reduced sunlight during the flowering period in the three provinces of Northeast China. Results showed that the critical thresholds for light, temperature, and water stress index during the flowering stage of mild, moderate, and severe cold vortex types were [0, 0.21), [0.21, 0.32), and [0.32, 0.64], respectively. The rates of yield loss were [0, 0.03), [0.03, 0.08), and [0.08, 0.096], respectively. Based on the verification results of a total of 751 samples in 11 random years from 1961 to 2020, the percentage of stations for which the production reduction grade, as calculated by the composite index developed in this study, aligning with the actual production reduction grade was 63.7%, consistently exceeding 58.0% annually. Moreover, the proportion of sites with a similarity or difference level of 1 stood at 88.3%, surpassing 85.0% in each year. The index could effectively assess the extent of rice yield loss caused by cold vortex disasters in Northeast China.

Effects of Nitrogen Fertilizer Reduction Combined with Foliar Fertilizer Application on the Physiological Characteristics and Yield of High-Quality Japonica Rice

Effects of Nitrogen Fertilizer Reduction Combined with Foliar Fertilizer Application on the Physiological Characteristics and Yield of High-Quality Japonica Rice

Metabolomics Analysis of Variation in Grain Quality of High-Quality Japonica Rice

In recent years, the semi-glutinous japonica rice variety has been extensively utilized in Jiangsu Province to greatly increase rice quality. Nevertheless, the increasing occurrence of seed variation presented a major threat to rice quality. Enhancing the quality of rice grains has emerged as a critical factor in guaranteeing consumer acceptance. Throughout this investigation, five lines (VJ1, VJ2, VJ3, VJ4, and VJ5) selected from the Nanjing9108 population in Liyang were used as research materials, and original cultivars of Nanjing9108 (CKJ1) provided by the original breeder were utilized as control materials to compare rice quality and differential metabolites. VJ4 and VJ3 demonstrated a significant reduction in milled rice rate and head milled rice rate when contrasted to CKJ1. Compared with CKJ1, the amylose content of the five strains was significantly increased. Only VJ3 amplified the 106 bp target band, and its 2-AP content was 0 ng/g. Most metabolites are mainly enriched in cutin, suberine, wax biosynthesis, histidine, and tryptophan metabolism. The primary metabolites throughout the metabolic pathway involve lipids and lipid-like molecules (mono palmitin, alpha-eleostearic, and palmitic acid) and amino acid metabolites (L-glutamate, L-tryptophan, and L-serine). The identification of these key metabolites helps in the discovery of prospective biomarkers for screening seed variation throughout seed production.

Effects of dynamic nitrogen application on rice yield and quality under straw returning conditions

Rice cultivation in Jilin Province, China, encounters challenges associated with straw management and nitrogen fertilizer usage. This study explores the effects of dynamic nitrogen fertilizer application combined with straw incorporation on soil properties, rice yield, and quality. High-quality Japonica rice varieties, “Jihong 9″ and “Jinongda 853,” were cultivated in a 3-year trial across different regions. Results showed that dynamic nitrogen fertilizer application under straw incorporation significantly improved soil properties, leading to increased yields. Over the years, the average yield in straw retuning (SR) was 10,566 kg/ha, surpassing conventional practices (CK) at 9939 kg/ha. SR exhibited higher effective tiller rates, spike numbers, and grain numbers per spike, contributing to enhanced yields. Quality analysis revealed that SR rice exhibited lower protein content, resulting in reduced chalkiness and improved taste quality, making it a more desirable option. These findings highlight the effectiveness of sustainable agricultural practices in optimizing rice production in Jilin Province.

Varietal differences of japonica rice: Intrinsic sensory and physicochemical properties and their changes at different temperatures

In this study, changes in the physicochemical and sensory properties of seven japonica rice cultivars mainly consumed in Korea were investigated at different storage temperatures. Our results showed no distinct varietal differences in recovery properties, moisture, protein, and amylose contents. In contrast, storage conditions had a considerable effect on physicochemical properties, such as germination rates, seed viability, guaiacol oxidation, fatty acid values, adhesiveness, and all sensory attributes. The results indicated that higher temperatures led to more rapid degradation rates and oxidative reactions. Sindongjin and Samkwang were the most preferred cultivars immediately after harvest. However, they had low storage stability, owing to poor sensory and physicochemical properties, such as germination rates, seed viability, and fatty acid values. Unkwang, the only early maturing variety, had the highest storage stability despite showing the lowest physicochemical and sensory qualities immediately after harvest. Nevertheless, the differences in these cultivars were insignificant. In particular, the varietal differences in physicochemical and sensory properties were negligible when the refrigeration temperature was maintained. Therefore, we suggest that control of storage conditions increases the rice quality more than selection for cultivar types because high-quality japonica rice cultivars are already standardized.

Grain yield improvement in high-quality rice varieties released in southern China from 2007 to 2017

In recent years, high-quality rice varieties have been widely cultivated for food production in southern China. However, changes in the yield performance of different high-quality rice varieties are still unclear. In this study, the yield and yield components of 710 different types (hybrid or inbred rice and japonica or indica) of high-quality rice varieties were investigated in six provinces from 2007 to 2017. The results showed that, from 2007 to 2017, the grain yield and yield traits, including the number of spikelets per panicle and seed-set percentage, of high-quality indica rice varieties increased significantly, while the number of panicles decreased only in indica inbred rice. The grain yield of high-quality japonica rice also increased significantly, whereas japonica hybrid rice increased the number of spikelets per panicle and decreased the number of panicles. Compared with inbred rice, hybrid rice had a significant increase in grain yield due to a higher number of spikelets, rather than a lower number of panicles and seed-set percentage. Meanwhile, japonica rice showed higher grain yield than indica rice, which was attributed to seed-set percentage and an optimized structure between the number of panicles and the number of spikelets. In addition, the coefficient of variation of the grain yield of japonica rice decreased, whereas that of indica rice increased over time, and those of the number of panicles and seed-set percentage remained stable. Among the six provinces, Zhejiang had the highest grain yield because the number of spikelets per panicle and seed-set percentage increased over time. Our results suggested that, based on an increase in the yield potential of high-quality rice varieties over the past 11 years, future breeding of high-quality rice should be emphasized to improve the number of panicles and seed-set percentage for hybrid rice and the number of spikelets for inbred rice, especially the grain weight for indica inbred rice.

Effects of High Temperature on Quality of Japonica Rice at Early and Middle Heading Stage under Different Planting Modes

With the intensified greenhouse effect, high temperature has gradually become an adverse factor in growth of rice. Transplanting (TP) and direct seeding (DS) are two common rice planting modes. At present, the response of rice quality to high temperature under different planting modes and at different growth stages have not yet to be identified. Therefore, in our study, high-quality japonica rice Nanjing 9108 (NJ9108) and Nanjing 46 (NJ46) were cultivated through TP and DS under the setting of normal temperature (NT), moderate heating (2 °C higher than NT, MT) and extreme high temperature (5 °C higher than NT, HT) at early heading stage (EH, 0–14 d after heading) and middle heading stage (MH, 15–28 d after heading) respectively. The results showed that better resistance to high temperature was achieved with TP. The head rice rate, gel consistency and amylose content of rice decreased with the increase of temperature, while chalkiness degree, setback viscosity, average particle size, crystallinity and gelatinization temperature were opposite. Compared with high temperature at MH, the effect of EH on rice quality was more significant. In terms of varieties, the resistance to high temperature was stronger for NJ46 relative to NJ9108, mainly because NJ46 has a longer growth period and can avoid the stress of high temperature at heading stage. Above all, our results suggest that NJ46 could have better resistance with a longer growth period through TP under background of climate warming.

Genome-wide association studies of yield-related traits in high-latitude japonica rice

BackgroundHeilongjiang Province is a high-quality japonica rice cultivation area in China. One in ten bowls of Chinese rice is produced here. Increasing yield is one of the main aims of rice production in this area. However, yield is a complex quantitative trait composed of many factors. The purpose of this study was to determine how many genetic loci are associated with yield-related traits. Genome-wide association studies (GWAS) were performed on 450 accessions collected from northeast Asia, including Russia, Korea, Japan and Heilongjiang Province of China. These accessions consist of elite varieties and landraces introduced into Heilongjiang Province decade ago.ResultsAfter resequencing of the 450 accessions, 189,019 single nucleotide polymorphisms (SNPs) were used for association studies by two different models, a general linear model (GLM) and a mixed linear model (MLM), examining four traits: days to heading (DH), plant height (PH), panicle weight (PW) and tiller number (TI). Over 25 SNPs were found to be associated with each trait. Among them, 22 SNPs were selected to identify candidate genes, and 2, 8, 1 and 11 SNPs were found to be located in 3′ UTR region, intron region, coding region and intergenic region, respectively.ConclusionsAll SNPs detected in this research may become candidates for further fine mapping and may be used in the molecular breeding of high-latitude rice.

Differences in lamina joint anatomy cause cultivar differences in leaf inclination angle of rice

ABSTRACTLeaf erectness is an important agronomic trait for improving canopy photosynthesis in rice. It is well known that leaf inclination angle (LIA) decreases after expansion during ripening. However, the high-yielding indica cultivar ‘Takanari’ retains a greater LIA during ripening than the high-quality japonica cultivar ‘Koshihikari’. To clarify the cause of the cultivar difference in LIA, we investigated anatomical characteristics of the lamina joint of a flag leaf. We found a close linear correlation between LIA at the centre and at the base of the leaf blade in both cultivars during ripening. The length of the lamina joint increased significantly more on the adaxial side of a leaf (the margin of the collar) than on the abaxial side (the abaxial side of the central part of the collar) in ‘Koshihikari’ after leaf expansion, but there was no clear difference in ‘Takanari’. We found a close linear correlation between the ratio of lamina joint length on the adaxial to abaxial sides and LIA in ‘Koshihikari’ and ‘Takanari’ during ripening. In ‘Koshihikari’, the average length of cells on the adaxial side increased significantly after leaf expansion, with no significant increase in that on the abaxial side and no significant change in cell number on either side. In ‘Takanari’, cell length and cell number showed no significant changes on either side of the lamina joint. We conclude that the cultivar difference in LIA during ripening is caused mainly by cell elongation on the adaxial side of the lamina joint.List of Abbreviations: k: light extinction coefficient; LIA: leaf inclination angle; QTL: quantitative trait locus

First Report of Sclerotium hydrophilum Causing Stem Rot of Rice in Northeast China

In August 2016, rice plants with brown to black lesions with irregular shape and water-soaked margins in leaf sheaths were observed in Baoqing county in Heilongjiang province, Northeast China. To isolate the causal pathogen, pieces of symptomatic leaf sheaths were treated with 1% NaClO for 1 min, rinsed with sterile distilled water for 2 min, and then transferred to potato dextrose agar (PDA) medium for incubation at 28°C. The cultivated mycelium was transferred to new PDA medium. Colonies of pure cultures on new PDA medium were initially white and turned brown about 3 weeks later. The hyphal width was measured with a range of 4.5 to 6.2 μm. Large numbers of small and globose sclerotia were observed on surface of the colonies at 3 days after subculturing. The sclerotia were white at first and then turned black over time. The diameters of sclerotia ranged from 0.31 to 0.54 mm with an average of 0.41 mm (n = 50). DNA of a representative isolate named Hbq001 was extracted, and the 18S rDNA region was amplified by PCR with universal primer pair NS1/NS6 (White et al. 1990). The 18S rDNA sequence of isolate Hbq001 (GenBank accession no. KY995575) shared 99.7% nucleotide identities with those of Sclerotium hydrophilum (GenBank accession no. KC354147). Therefore, based on these cultural characteristics and rDNA sequence, isolate Hbq001 was identified as S. hydrophilum (Demirci et al. 2009). To complete Koch’s postulates, 4 mm diameter PDA disks containing mycelium and sclerotia of S. hydrophilum isolate Hbq001 were placed on the stem of 4-week-old healthy rice seedlings and wrapped with Parafilm. Sterile PDA disks were used as controls. After 4 days at 28°C, symptoms similar to those in the field were observed on the inoculated seedlings but not on control plants. Finally, the fungus S. hydrophilum, which showed the same cultural characteristics as described above, was reisolated from the inoculated seedlings. In China, S. hydrophilum was first identified in Yunnan province and was found to be distributed in southern China (Hu et al. 2008; Ruan and Chen 2002; Wang et al. 2013). Northeast China is a major rice-producing region. Differing from the rice-producing areas of southern China, this region has specific climatic conditions with cold temperature and abounds in high-quality japonica rice. To our knowledge, this is the first report of S. hydrophilum in the cold northern region of China.

Development and Evaluation of Near-Isogenic Lines with Different Blast Resistance Alleles at the Piz Locus in japonica Rice from the Lower Region of the Yangtze River, China.

Rice blast, caused by Magnaporthe oryzae, threatens rice production in most of the rice-growing areas in China, especially in regions that have grown Oryza sativa subsp. japonica in recent years. The use of resistance genes is the most effective and economical approach for blast control. In our study, a set of six near-isogenic lines (NIL) were developed by introgression of six resistance alleles of the Piz locus (Pi2, Pigm, Pi40, Pi9, Piz, and Pizt) into a blast-susceptible, high-yielding, high-quality japonica '07GY31' via marker-assisted backcross breeding. Artificial inoculation using 144 M. oryzae isolates collected from the lower region of the Yangtze River, China, revealed that most of the NIL, including NIL-Pi2, NIL-Pigm, NIL-Pi40, NIL-Pi9, and NIL-Pizt, exhibited broad-spectrum resistance against rice blast at the seedling stage, with resistance frequencies (RF) of 93.06 to 98.61%. NIL-Piz was an exception, with an RF of 21.53%, which was slightly higher than the recurrent parent 07GY31. NIL-Pi40 and NIL-Pigm had broad-spectrum resistance (RF of 93.33 and 71.67%, respectively) at the heading stage following inoculation of 60 isolates of M. oryzae. Field trials with artificial inoculation at the seedling and heading stage showed that NIL-Pigm and NIL-Pi40 were highly resistant in four locations under high disease pressure. NIL-Pizt showed effective resistance in three locations from Zhejiang and Jiangsu Provinces. This study shows that O. sativa subsp. japonica alleles of the Piz locus confer resistance to M. oryzae, and provides an effective method to enhance seedling and panicle blast resistance in rice plants in the lower region of the Yangtze River, China.

QTL Mapping of Grain Quality Traits Using Introgression Lines Carrying Oryza rufipogon Chromosome Segments in Japonica Rice.

BackgroundImproved eating quality is a major breeding target in japonica rice due to market demand. Consequently, quantitative trait loci (QTL) for glossiness of cooked rice and amylose content associated with eating quality have received much research focus because of their importance in rice quality.ResultsIn this study, QTL associated with 12 grain quality traits were identified using 96 introgression lines (IL) of rice developed from an interspecific cross between the Korean elite O. sativa japonica cultivar ‘Hwaseong’ and O. rufipogon over 7 years. QTL analyses indicated that QTL qDTH6 for heading date, detected on chromosome 6 is associated with variance in grain traits. Most QTLs detected in this study clustered near the qDTH6 locus on chromosome 6, suggesting the effect of qDTH6. O. rufipogon alleles negatively affected grain quality traits except for a few QTLs, including qGCR9 for glossiness of cooked rice on chromosome 9. To characterize the effect of the O. rufipogon locus harboring qGCR9, four lines with a single but different O. rufipogon segment near qGCR9 were compared to Hwaseong. Three lines (O. rufipopgon ILs) having O. rufipogon segment between RM242 and RM245 in common showed higher glossiness of cooked rice than Hwaseong and the other line (Hwaseong IL), indicating that qGCR9 is located in the 3.4-Mb region between RM242 and RM245. Higher glossiness of cooked rice conferred by the O. rufipogon allele might be associated with protein content considering that three lines had lower protein content than Hwaseong (P < 0.1). These three O. rufipogon ILs showed higher yield than Hwaseong and Hwaseong IL due to increase in spikelets per panicle and grain weight indicating the linkage of qGCR9 and yield component QTLs.ConclusionThe qGCR9 locus is of particular interest because of its independence from other undesirable grain quality traits in O. rufipogon. SSR markers linked to qGCR9 can be used to develop high-quality japonica lines and offer a starting point for map-based cloning of genes underlying this trait. To our knowledge, this is the first report to map a beneficial QTL for glossiness of cooked rice from a wild rice, O. rufipogon.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-016-0135-0) contains supplementary material, which is available to authorized users.

Ultrastructure of Individual and Compound Starch Granules in Isolation Preparation from a High-Quality, Low-Amylose Rice, Ilpumbyeo, and Its Mutant, G2, a High-Dietary Fiber, High-Amylose Rice

The ultrastructures of isolated starch granules from Ilpumbyeo (IP), a low-amylose japonica rice, and its mutant, Goami2 (G2), a high-amylose rice, which have extreme contrasts in physicochemical properties, cooking qualities (Kang, H. J.; Hwang, I. K.; Kim, K. S.; Choi, H. C. Comparative structure and physicochemical properties of Ilpumbyeo, a high-quality japonica rice, and its mutant, Suweon 464. J. Agric. Food Chem. 2003, 51, 6598-6603. Kim, K. S.; Kang, H. J.; Hwang, I. K.; Hwang, H. G.; Kim, T. Y.; Choi, H. C. Comparative ultrastructure of Ilpumbyeo, a high-quality japonica rice, and its mutant, Suweon 464: Scanning and transmission electron microscopy studies. J. Agric. Food Chem. 2004, 52, 3876-3883), and susceptibility to amylolytic enzymes (Kim, K. S.; Kang, H. J.; Hwang, I. K.; Hwang, H. G.; Kim, T. Y.; Choi, H. C. Fibrillar microfilaments associated with a high-amylose rice, Goami2, a mutant of Ilpumbyeo, a high-quality japonica rice. J. Agric. Food Chem. 2005, 53, 2600-2608), were compared. In isolated preparation, IP consisted entirely of well-separated individual starch granules (ISG), whereas G2 consisted of two populations, the large voluminous bodies and the smaller forms, the ISGs. High-voltage electron microscopy revealed that each of the voluminous bodies consisted of tightly packed smaller subunits, the ISGs, indicating that they represent the compound starch granules (CSGs) of G2. This suggests that the structural as well as functional unit of G2 involved in food processing is, unlike IP and other ordinary rices, not ISG but is primarily CSG. ISGs located at the periphery of CSGs were fused to each other with adjacent ones forming a thick band or wall encircling the entire circumference. The periphery of ISGs separated from CSGs of G2 consisted of thin radially oriented filaments arranged side by side along the entire granule surface, whereas no such filaments occurred in ISG of IP. It appears that the thick band and the peripheral filaments surrounding CSGs and ISGs, respectively, function as a structural barrier that limits the entrance of water into the granules and subsequent absorption, causing the low swelling power, incomplete gelatinization, and finally poor quality of cooked rice in G2.

Fibrillar Microfilaments Associated with a High-Amylose Rice, Goami 2, a Mutant of Ilpumbyeo, a High-Quality Japonica Rice

The ultrastructure of cooked and malt-treated cooked rice of Ilpumbyeo (IP) and its mutant Goami 2 (G2), which have extreme contrasts in physicochemical properties, cooking quality, and ultrastructural characteristics in raw grains (1, 2), was compared. In cooked rice of IP, starch granules in endosperm cells were evenly coalesced, appearing as homogeneously smooth sheetlike matrix and/or globules, whereas those in G2 were a heterogeneously coarse matrix in which a novel structural feature, the microfilaments, was embedded. In malt-treated cooked rice of IP, most starch was hydrolyzed by the malt enzymes, appearing as empty vacuoles surrounded by the cell wall, whereas that in G2 was highly resistant to malt treatment, remaining as distinct structural features, the malt-resistant compound starch granules. The property of G2's compound starch granules, which are tolerant of mechanical and chemical treatments thereby retaining their structural integrity (2) and of cooking and malt treatment thereby retaining their physical hardness, appears to play a major role in determining the quality of cooked rice of G2.

Comparative Ultrastructure of Ilpumbyeo, a High-Quality Japonica Rice, and Its Mutant, Suweon 464: Scanning and Transmission Electron Microscopy Studies

A new rice mutant Suweon 464 (S-464), which has extreme contrast in cooking quality and physicochemical properties from those of its mother variety Ilpumbyeo (IP), revealed striking differences in ultrastructure in in situ, fractured whole grain, and isolated starch preparation. In scanning electron microscopy (SEM), compound starch granules (CSG) in whole grains of IP were readily split during fracturing, whereas those in S-464 were structurally intact and were enclosed within a sac-like structure tolerant of fracturing. In isolated preparation, IP starch consisted entirely of individual starch granules, whereas S-464 starch consisted of mostly large CSG enclosed within the sac, preventing the release of the individuals. In transmission electron microscopy (TEM), S-464 starch granules were smaller, solidly "condensed", and highly contrasted, whereas those of IP were larger, loosely "diffused", and less contrasted. The boundaries of amyloplasts and starch granules in S-464 were coated with a thin proteinaceous layer, presumed to be the counterpart of the sac that enclosed the CSG observed in SEM.

Comparative structure and physicochemical properties of Ilpumbyeo, a high-quality japonica rice, and its mutant, Suweon 464.

A new rice mutant Suweon 464 (S-464) derived from a high-quality rice, Ilpumbyeo (IP), revealed a striking difference in cooking quality from IP. The physicochemical properties of S-464 and IP were compared. S-464 was unusually high in amylose and fiber contents, had B-type crystallinity of starch, and had a markedly lower proportion of short chains in the distribution of glucan-chain fractions of debranched starch as compared with IP. Scanning electron microscopy revealed that starch granules of S-464 were much smaller in size than those of IP and that many of them were not separated from amyloplasts. The physicochemical properties of S-464 would contribute to poor gelatinization, lower swelling power, higher hardness, and less stickiness when cooked. Although S-464 may not be desirable for cooked rice, the mutant could be an excellent candidate for other processed food products on the basis of its unusual properties of starch and high fiber, protein, and lipid contents.