Amylose Rice Research Articles

Variation of Wx microsatellite allele, waxy allele distribution and differentiation of chloroplast DNA in a collection of Thai rice (Oryza sativa L.)

Eighty-two varieties of rice from different regions in Thailand were selected to explore the Waxy(Wx)gene diversity and indica-japonica differentiation of chloroplast DNA. A comparison of the 5’ splice site in the first intron was made between glutinous and nonglutinous rice. It revealed that non-glutinous with low-amylose content and glutinous rice were characterized as the Wxb allele based on the G-to-T base substitution, whereas non-glutinous rice with intermediate and high amylose carried the Wxa allele. Four Wx microsatellite alleles, (CT)n repeat, (n = 16,17,18 and 19) were found in glutinous rice. In contrast, non-glutinous rice showed five Wx microsatellite alleles (n = 11, 16, 17, 18 and 19). The (CT)17 allele was prominent allele in Thai population, while the (CT)11 allele was found only in intermediate and high amylose rice varieties from southern Thailand. Almost all of upland rice grown by various ethnic groups in northern Thailand were characterized as japonica type based on their having the PstI-12 fragment in their cpDNA, whereas most of rainfed lowland varieties from other regions of Thailand were indica. This exploration of DNA-based genetic markers is important, as it enhances our ability to describe and manipulate sources of genetic variation for rice breeding programs.

Effect of Endosperm Whiteness pf Low Amylose Rice Variety "Takitate" cultivated in Miyagi prefecture in 2003

Effect of Endosperm Whiteness pf Low Amylose Rice Variety "Takitate" cultivated in Miyagi prefecture in 2003

Optimization of Drum Drying Parameters for Low Amylose Rice (KDML105) Starch and Flour

An attempt was made to study and model the effects of drum drying process variables on the physico–chemical properties of low amylose rice (KDML105) flour and starch. Drum surface temperature, holding time and solid content of the slurry were varied at three levels: 115–135°C, 14–84 s and 20–40%, w/w, respectively. The dependent variables were moisture content (MC), degree of gelatinization (DG), water absorption index (WAI), water solubility index (WSI) and pasting property. High solid content led to a decrease in DG, WAI and initial peak viscosity (IPV) and increase in WSI of dried samples. Longer holding time resulted in increased DG while surface temperature had no significant effect on all characteristics. Predictive correlations were developed using stepwise multiple linear regression to predict MC, DG, WAI, WSI, and IPV of dried products from drum drying variables.

Prediction of grain weight, brown rice weight and amylose content in single rice grains using near-infrared reflectance spectroscopy

The potential of near-infrared reflectance spectroscopy (NIRS) for simultaneous analysis of grain weight (mg), brown rice weight (mg) and milled rice amylose content (AC, %) in single rice grains was studied. Calibration equations were developed using 474 single grain samples, scanned as both rice grain and brown rice. An independent set containing 90 F 2 generation grains was used to validate the equations. In general, equations developed using the first derivative resulted in superior calibration and validation statistics compared with the second derivative and those developed using brown rice were superior to those developed from the rice grain. Fitting equations were developed and monitored with an external validation set. The standard error of prediction (corrected for bias) SEP(C) for AC, brown rice weight and rice grain weight for equations developed using brown rice were 2.82, 1.09 and 1.30, with corresponding coefficient of determinations ( r 2) of 0.85, 0.71 and 0.67, and SEP(C)/S.D. of 0.39, 0.57 and 0.59, respectively. It was demonstrated that NIRS provides a convenient way to screen single intact grains. This will be advantageous in early generation selection in rice breeding programs.

Effect of Amylose Content on Gelatinization, Retrogradation and Pasting Properties of Flours from Different Cultivars of Thai Rice

AbstractPresently, rice cultivars are categorized according to amylose content into three groups: low, medium and high amylose content cultivars. The correlation of amylose content with gelatinization properties, retrogradation, and pasting properties of eleven cultivars of Thai rice were investigated. Rice flour was prepared from milled rice by the wet grinding process. Onset (To), peak (Tp) and conclusion (Tc) temperatures of gelatinization, (determined by DSC) were found to be highly positively correlated with amylose levels. This correlation could be used for prediction of amylose content of rice flour. Low amylose starch could also be characterized by low degree of retrogradation (%R). The data obtained from RVA‐viscograms (peak viscosity, breakdown, setback, and pasting temperature) can be used only for characterization of the group of low amylose starches (waxy rice). It was demonstrated that low amylose rice starch provided the highest peak viscosity and breakdown and the lowest setback and pasting temperature among the groups investigated.

Cloning and characterization of the granule-bound starch synthase II gene in rice: gene expression is regulated by the nitrogen level, sugar and circadian rhythm.

A full-length coding domain sequence of a gene analogous to granule-bound starch synthase (GBSS; ADP-glucose-starch glucosyltransferase, EC 2.4.1.21) was cloned and defined as OsGBSSII based on a Nitrogen (N)-starvation-induced cDNA library constructed using the rapid subtraction hybridization method. The deduced amino acid sequence of OsGBSSII was 62-85% identical to those of GBSS proteins from other plant species. The exon/intron organization of OsGBSSII was similar to that of OsGBSSI. OsGBSSII was mainly expressed in leaves and its protein was exclusively bound to starch granules in rice leaves, which suggests that the amylose in rice leaves is synthesized by OsGBSSII. N-starvation-induced expression of OsGBSSII could be repressed by supplying nitrate, ammonia or amino acid (glutamic acid or glutamine), glucosamine (an inhibitor of hexokinase) or dark conditions. These results indicate that N-starvation induction was dependent on the photosynthetic product and hexokinase in rice leaves. Sugars induced the accumulation of OsGBSSII transcripts in excised leaves through glycolysis-dependent pathways. OsGBSSII gene expression is regulated by the circadian rhythm in rice leaves.

Duplicated coding sequence in the waxy allele of tropical glutinous rice ( Oryza sativa L.)

Rice starch consists of amylopectin and amylose, the latter component being controlled by the Waxy ( Wx) gene. Two alleles Wx a and Wx b were found to regulate the quantitative level of the Wx protein as well as the amylose content. A comparison of the genomic sequences of rice Wx genes responsible for the synthesis of grain amylose was made between two pairs of glutinous and non-glutinous reverse mutants. By comparing their 5′ splice codons in the first intron, the low-amylose and glutinous rices were characterized as the Wx b allele based on the G-to-T base substitution, which caused an aberrant splicing. When the entire genomic sequences of Wx b were compared, a unique duplication of 23 bp was found to be present only in the glutinous mutants. This 23 bp insertion was truly unique for tropical glutinous rice because of its similarity between the 800 bp sequences around the duplicated sequences of 24 glutinous varieties and two annual diploid wild rice accessions. This in-frame duplication created a premature translation stop codon at 78 bp downstream. The insertion was unique and none of the structure was identical to any transposon or retrotransposon ever reported in rice before. This unique duplicated sequence opens up opportunities to develop PCR-based markers useful for classifying grain amylose in rice.

Properties of Starches from Several Low‐Amylose Rice Cultivars

ABSTRACTThe starch properties of five low‐amylose rice cultivars, Yawarakomachi, Soft 158, Hanabusa, Aya, and Snow Pearl, were compared with those of two normal amylose rice cultivars, Nipponbare and Hinohikari. There were no large differences in the distributions of the amylopectin chain length determined by high‐performance anion‐exchange chromatography, and the starch gelatinization properties determined by differential scanning calorimetry, between normal and low‐amylose rice cultivars. Results obtained using rapid viscosity analysis indicated that low‐amylose rice starches had lower peak viscosity, breakdown, and setback values than normal amylose rice starches. Starch granules from low‐amylose rice cultivars had a higher susceptibility to glucoamylase than those from normal amylose rice cultivars. The results of this study showed some differences between normal and low‐amylose rice starches in pasting properties and enzymatic digestibility.

Influence of Pine Nut (Pinus koraiensis) Oil Fractions on Physicochemical Properties of Rice Starch Solutions

AbstractThe physicochemical properties of rice starch suspensions effected by interactions with pine nut oil fractions were investigated. Oil fractions (crude pine nut oil, glycolipid, nonpolar lipid, gums, and degummed oil) from pine nut (Pinus koraiensis) were prepared by solvent extraction and addition of boiling water. The influence of the fractions on the physicochemical properties of rice amylose solution (5%, w/w) was determined by measuring the complexing index, absorbance ratio (630/520 nm), colour, rheological characteristics, and microscopic structure at various concentrations. Their effect on rice starch swelling power was also determined. The glycolipid fraction had the highest complexing index with rice amylose. Rice amylose solutions containing the glycolipid fraction exhibited greater pseudoplastic fluid (n<0.7) behaviour, higher colour difference values, and lower absorption ratios (1.64‐1.48) than did those containing other fractions. Hydrated oil fraction (gums) complexed with amylose only poorly, if at all, but amylose solutions containing them had rheological properties similar to those containing the glycolipid fraction. The addition of oil fractions increased the swelling power value compared to the control.

Effect of Raw Material Preparation on Rice Vermicelli Quality

The physicochemical properties of high amylose rice flour prepared from wet milling and dry milling were examined and the rice vermicelli quality made from these flour samples was evaluated. The effect of flour particle size on rice vermicelli quality was also determined. The milling method affected chemical compositions and all physicochemical properties of the flour. A higher degree of starch damage occurred in drymilled flour. Rice vermicelli made from dry-milled flour had higher cooking losses and softer texture than that made from wet-milled flour and the commercial reference products. Flour particle size influenced both cooking and textural quality of rice vermicelli but did not influence the water absorption index. Flours with larger particle sizes gave vermicelli with higher cooking loss and less desirable texture than flours with smaller particle sizes. Flour with particle sizes less than 200 mesh produced acceptable vermicelli in terms of cooking and textural quality.

Interaction of rice bZIP protein REB with the 5?- upstream re-gion of both rice sbe1 gene and waxy gene

Rice starch branching enzyme 1 (SBE1) and granule-bound starch synthase (GBSS) catalyzed the biosynthesis of amylopectin and amylose in rice developing endosperm respectively, and the genes encoding these two enzymes, sbe1 and waxy, are mainly expressed in the endosperm. Within the 5′-upstream region of rice sbe1 gene, we identified a 53 bp fragment C53 which could interact with the nuclear proteins extracted from rice endosperm. We also found that fragment Ha-2 in the 5′-upstream region of rice waxy gene could compete with C53 for its interaction. Further experiments demonstrated that rice bZIP protein REB could interact with two ACGT elements (G-box and Hex) in the fragment C53 as well as three ACGT elements (WG1, WG2, and WG3) in the fragment Ha-2. The WG1 element could compete well with Hex element for its interaction with REB. These results suggested that the expression of sbe1 and waxy gene in rice developing endosperm may be coordinately regulated by REB-like bZIP transcriptional factors.

Freezing and Thawing Conditions Affect the Gel Stability of Different Varieties of Rice Flour

The freeze-thaw stabilities of three different rice flour gels (amylose rice flour with 28% amylose, Jasmine rice flour with 18% amylose and waxy rice flour with 5% amylose) were studied by first freezing at –18 °C for 22 h and subsequent thawing in a water bath at 30 °C, 60 °C and 90 °C, or by boiling in a microwave oven. The freeze-thaw stability was determined for five cycles. Starch gels thawed at higher temperature exhibited a lower syneresis value (percent of water separation) than those thawed at lower temperature. Amylose rice flour gels gave the highest syneresis values (especially at the first cycle). The Jasmine rice flour gels gave a higher syneresis value than the waxy rice flour gel. Except for freezing by storage at –18 °C and thawing at 30 °C, there was no separation of water at any cycle when waxy rice flour gel was thawed at any temperature, irrespectively of the freezing methods used. Cryogenic Quick Freezing (CQF) followed by storage at –18 °C and then thawing (by boiling or by incubation at any other temperatures) gave lower syneresis values than all comparable samples frozen by storage at –18 °C. The order of syneresis values for the three types of rice flour was waxy rice flour Jasmine > amylose rice flour.

低アミロース水稲品種「ソフト158」および有望系統「北陸180号」の施肥反応

低アミロース水稲品種「ソフト158」および有望系統「北陸180号」の施肥反応

DETERMINATION OF UNDRIED ROUGH RICE CONSTITUENT CONTENT USING NEAR-INFRARED TRANSMISSION SPECTROSCOPY

Near-infrared transmission (NIRT) spectroscopy was used in an attempt to predict moisture content, proteincontent and amylose content from undried whole-grain rough rice spectra. One hundred-fifty undried rough rice sampleswere collected. Using partial least squares calibration models obtained from undried whole-grain rough rice spectra, thecoefficient of determination (r 2) and the standard error of prediction (SEP) of the validation set were r 2 = 0.96 andSEP = 0.70 for rough rice moisture content, r 2 = 0.70 and SEP = 0.24 for brown rice protein content, r 2 = 0.76 andSEP = 0.22 for milled rice protein content, and r 2 = 0.00 and SEP = 0.27 for milled rice amylose content. The results ofthe validation indicated that NIRT could be used to determine moisture content and protein content. Thus, NIRTtechnology may be used to classify undried rough rice into qualitative groups such as high protein content rice and lowprotein content rice upon arrival at a rice-drying facility after harvesting.

Evaluating Techniques for Rice Grain Quality Using near Infrared Transmission Spectroscopy

The development of advanced evaluation techniques for rice quality has been a desire of the Japanese rice industry (breeding, distribution and processing). The objective of the present study is to develop novel techniques for evaluating rice grain quality. A reliable determination method for amylose in whole grain rice using near infrared transmission (NIT) is proposed, using Partial Least Squares (PLS) regression analysis. It was suggested from results based on two different validation methods that the PLS models have possibilities for determination of apparent amylose content using NIT spectroscopy. PLS modelling for constituents important in rice quality indicates that reasonably accurate models are attainable for moisture content and protein content in whole grain rice. However our PLS models were not sufficiently accurate for physical rice quality (head rice ratio, apparent density, whiteness) using NIT spectroscopy.

Physico-chemical Characteristics as Indicators of Starch Availability from Milled Rice

The hypothesis was tested that certain physico-chemical characteristics might be used as indicators of total starch availability and rate of starch availability of milled rice. Milled unparboiled (uPB) and parboiled (PB) rice samples (n=93) were characterized using standardized methods of physical tests and chemical analyses and anin vitromethod was used for measuring the rate of starch digestion on a subsample of rice (n=26). The rice varieties were dominated by medium long, bold rice grain with high amylose rice and intermediate gelatinization temperature (GT), but a wide range in all characteristics was measured. Small amounts of resistant starch (RS) were measured in the cooked rice, indicating virtually complete starch availability. The RS of PB rice (0·4 g/100 g rice as eaten) was significantly (P<0·004) higher than the RS of uPB rice (0·1 g/100 g) however. The rate of starch digestion was significantly affected by both variety and parboiling. The starch digestion index (SDI) values of the PB samples (mean value 73·7) were significantly (P<0·001) lower than those of the uPB samples (mean value 79·0). The apparent amylose content (AC) was the strongest determinant for SDI in both uPB and PB rice. The widths and shapes of the raw grains and the elongation after cooking were correlated significantly with SDI values for the uPB rice, while the relatively mild parboiling procedure followed in this study eliminated this correlation. The minimum cooking times were correlated significantly with the SDI values in the uPB samples.

Microsatellites and a single-nucleotide polymorphism differentiate apparentamylose classes in an extended pedigree of US rice germ plasm

The Waxy gene (Wx) encodes the granule-bound starch synthase responsible for the synthesis of amylose in rice (Oryza sativa). Recently, a polymorphic microsatellite sequence closely linked to the Wx gene was reported. To determine whether polymorphism in this sequence correlates with variation in apparent amylose content, we tested an extended pedigree of 92 current and historically important long-, medium- and short-grain US rice cultivars representing the efforts of many breeders over more than 80 years. Seven Wx microsatellite alleles were identified which together explained 82.9% of the variation in apparent amylose content of the 89 non-glutinous rice cultivars tested. Similar results were also obtained with 101 progenyof a cross between low- and intermediate-amylose breeding lines. An additional, unique microsatelliteallele, (CT)16, was detected in one glutinous cultivar,CI 5309. However, the other glutinous cultivars,Calmochi 101 and Tatsumi mochi, were in the (CT)17 class along with three other cultivars that contained15–16.5% amylose.

Optimisation of Germination Conditions by Response Surface Methodology of a High Amylose Rice (Oryza sativa) Cultivar

Germination conditions for a high amylose rice cultivar were optimised using response surface methodology. Germination time and temperature significantly affected the amylase activity and thiamin content of the subsequent flour. All germination conditions investigated significantly affected the malting loss while the change in cold paste viscosity was significantly influenced by steeping time, germination time and temperature. The yield or recovery was significantly affected by germination time only. Protein content was not altered significantly by the germination conditions investigated. Optimum germination conditions for high amylose rice were: steeping time 24 h at 25 °C or 16 h at 35 °C, germination time 3 d, germination temperature 30 °C. Values predicted at optimum conditions by the response surface model for malt loss, viscosity, amylase activity, yield and thiamin content were experimentally tested and close agreement between experimental and predicted values was observed.

Genetic Study on Milled Rice Amylose Content by Means of Single-Grain Amylose Analysis

Genetic Study on Milled Rice Amylose Content by Means of Single-Grain Amylose Analysis

Microscop of Rice Starch Granules During Cooking

AbstractStarch from five cultivars of rice was pasted in the Brabender viscograph and then held at 95°C for 60min. Granules were examined by light and scanning electron microscopy. In concentrated (12%) pastes, low‐amylose rice starch showed total granule disintegration after 60min of cooking at 95°C, but highamylose granules showed only marginal disorganization. Waxy starch granules were disintegrated even at 70°C. In dilute (1%) pastes, on the other hand, granules swelled without appreciable disruption, apparently more in low than in high amylose starch. Clearly low amylose starch granules were weak and fragile and so swelled as well disintegrated easily, while high amylose rice starch was relatively strong and rigid and so resisted swelling as well as disintegration. This relative regidity/fragility of starch granules seemed to be the key to differences in rice quality.