Low Amylose Content Research Articles

Effect of Different Starches on Edible Quality, In Vitro Starch Digestibility, and Antioxidant Property of Black Rice Noodle

AbstractAlthough the nutritional value of black rice (BR) is high, the low amylose content makes undesirable qualities in black rice noodle (BRN) and leads to low levels of acceptance by consumers. In this work, mung bean starch (MBS), potato starch (PS), and corn starch (CS) are added (30% w/w based on BR) to BRN and the effects on the edibility, in vitro starch digestibility, and antioxidant properties are investigated. The results show that starches significantly reduced the cooking loss from 30.80% to 10.80% and broken rate from 44.43% to 0.00%, and increased the springiness and the extensibility properties of BRN while maintaining the low in vitro starch digestibility by characterizing the content of rapidly digestible starch (RDS), slowly digestible starch (SDS), and resistant starch (RS). Starches reduce the loss of total polyphenols of BRN during cooking, improve the release rate of polyphenols in the intestinal digestion, and maintain high DPPH and ABTS radical scavenging rate. Furthermore, scanning electron microscope (SEM) reveals that starches stabilized the microstructure of BRN by forming hydrogen bonds with BR and interfering with the reassociation of starch chains (confirmed by low field nuclear magnetic resonance (LF‐NMR), X‐ray diffraction XRD, Fourier transform‐infrared spectroscopy (FT‐IR), and rapid visco analyzer (RVA)). MBS shows the most positive effect on edible quality of BRN.

Water migration, texture and oral processing properties of semi-waxy rice during retrogradation.

Semi-waxy rice, a low-amylose content (8%-13%) rice variety, can resist retrogradation. It is becoming more and more popular and widely cultivated in East China where consumers prefer cooked rice with soft and tender texture. In this study, water migration, texture and oral processing properties of cooked rice during retrogradation were investigated in order to characterize semi-waxy rice. The results confirmed that the water mobility and migration of semi-waxy rice during retrogradation is weaker than that of waxy rice and stronger than that of nonwaxy rice. Simultaneously, the hardness of semi-waxy rice was higher than that of waxy rice and lower than that of nonwaxy rice. The oral processing properties confirmed that freshly waxy rice was too adhesive and needed more work to breakdown slow breakdown structure (Type Ⅱ structure) compared to freshly semi-waxy rice. Meanwhile, nonwaxy rice was too hard, and more work was needed to break both fast breakdown structure (Type I structure) and slow breakdown structure (Type Ⅱ structure). The oral processing properties confirmed that retrograded semi-waxy rice generated more reducing sugar than retrograded waxy rice and nonwaxy rice. Thus, semi-waxy rice can retard retrogradation, and the texture of cooked semi-waxy rice is neither too adhesive as waxy rice nor too hard as nonwaxy rice. PRACTICAL APPLICATION: Semi-waxy rice cultivars have been widely cultivated in East China and well accepted by the consumers. This study aims to characterize semi-waxy rice and provide theoretical basis for semi-waxy rice study.

The impact of heat moisture treatment on the physicochemical properties and in vitro glycemic index of rice flour with different amylose contents and associated effects on rice dumpling quality

This study investigated the effects of heat moisture treatment (HMT) on the in vitro glycemic index and physicochemical properties of rice flour from two cultivars with different amylose contents. HMT decreased glycemic index and pasting viscosity, but increased pasting temperature and onset temperature relative to non-treated rice flour. High-amylose rice flour exhibited significantly higher pasting temperature and lower glycemic index than that with low amylose content. Rice flour dumplings prepared with 0, 40, 50, or 60% w/w HMT flour demonstrated differing texture profiles and sensory characteristics. Pearson's correlation showed that the amylose content of the rice flour used to make the dumplings was positively correlated (p < 0.01) with their hardness and negatively correlated (p < 0.01) with their adhesiveness, cohesiveness, and overall acceptance score. In addition, the glycemic index decreased with increasing HMT flour proportion. It was therefore concluded that HMT of rice flour could be used to achieve product acceptance with a lower glycemic index by compromising between physicochemical properties and sensory quality.

Generation of a New Glutinous Photothermosensitive Genic-Male-Sterile (PTGMS) Line by CRISPR/Cas9-Directed Mutagenesis of Wx in Rice (Oryza sativa L.)

The Photothermosensitive Genic-Male-Sterile (PTGMS) line, Y58S, an indica rice variety, combines high-quality and high-light-efficiency use, disease and stress resistance, and excellent plant type and mating force. Y58S is widely used to assemble two-line hybrid rice varieties, especially super hybrids. The Wx gene is the main effector gene for controlling amylose synthesis, which determines the amylose content (AC) of rice grains. By editing this gene, a glutinous line with a low AC can be obtained. In this study, the CRISPR/Cas9 system was used to mediate the editing of the Wx gene, which caused ultra-low AC mutations that produced a PTGMS glutinous rice strain with excellent waxiness. The results showed that 18 positively transformed plants were obtained from the T0 generation, with a mutation rate of 64.29%, of which six were homozygous mutant plants, indicating that the gene-editing target had a higher targeting efficiency and a higher homozygosity mutation rate. Compared to the wild type, the AC of the mutants was significantly lower. Through molecular marker detection and screening of T1 and T2 generations, five homozygous T-DNA-free mutant strains were identified that were consistent with Y58S in fertility and other agronomic traits except for AC. Among these, the AC of the W-1-B-5 homozygous mutant, the glutinous PTGMS line wx-Y58S, was as low as 0.6%. Our research revealed that the Wx gene of excellent PTGMS rice can be edited to generate a new waxy PTGMS line using the CRISPR/Cas9 system. This study provided a simple and effective strategy for breeding high-yield, high-quality, and glutinous two-line hybrid rice, and provided excellent sterile lines for their large-scale application. Once put into use, waxy hybrid rice will greatly improve the yield of glutinous rice and increase social benefits.

Genomic insight into balancing high yield, good quality, and blast resistance of japonica rice

BackgroundBalancing the yield, quality and resistance to disease is a daunting challenge in crop breeding due to the negative relationship among these traits. Large-scale genomic landscape analysis of germplasm resources is considered to be an efficient approach to dissect the genetic basis of the complex traits. Central China is one of the main regions where the japonica rice is produced. However, dozens of high-yield rice varieties in this region still exist with low quality or susceptibility to blast disease, severely limiting their application in rice production.ResultsHere, we re-sequence 200 japonica rice varieties grown in central China over the past 30 years and analyze the genetic structure of these cultivars using 2.4 million polymorphic SNP markers. Genome-wide association mapping and selection scans indicate that strong selection for high-yield and taste quality associated with low-amylose content may have led to the loss of resistance to the rice blast fungus Magnaporthe oryzae. By extensive bioinformatic analyses of yield components, resistance to rice blast, and taste quality, we identify several superior alleles for these traits in the population. Based on this information, we successfully introduce excellent taste quality and blast-resistant alleles into the background of two high-yield cultivars and develop two elite lines, XY99 and JXY1, with excellent taste, high yield, and broad-spectrum of blast resistance.ConclusionsThis is the first large-scale genomic landscape analysis of japonica rice varieties grown in central China and we demonstrate a balancing of multiple agronomic traits by genomic-based strategy.

Study on physicochemical properties of rice landraces for amylose, gel consistency and gelatinization temperature

Rice grain quality depends on physical, biochemical, cooking quality and organoleptic characters. Grain quality analysis in rice involves a physicochemical and sensory tests. In this study, morphologically different 60 rice landraces of Tamil Nadu along with ADT (R) 45 as a check variety were used for physicochemical analysis based on the amylose content (AC), gel consistency (GC) and gelatinization temperature (GT). Highly significant variation (p&lt;0.05) was observed among the 60 landraces for all the characters. Most of the landraces registered low amylose content. Nine landraces exhibited high and 18 landraces exhibited intermediate AC. In the case of a gel consistency, most of the landraces exhibited soft GC, while four landraces viz., Athur kichadi, Kavuni nel, Uppu mulagai and Valan registered medium gel. With respect to GT, all the landraces exhibited high to intermediate GT except Kattu ponni, Kavuni nel and Sugandni samba which were identified with low GT. The check variety exhibited intermediate amylose, soft gel and high gelatinization temperature. The landraces Chennellu, Kattu vanipam, Kichali samba, Kuttala samba, Pome, Revathi, Samba masanam, Saysree, Sembalai, Sivappu Kavuni, Soora kuruvai, Thailand Kavuni, Thanga samba and Thirupathisaram were identified as promising landraces based on intermediate amylose, soft gel consistency and intermediate gelatinization temperature. High genotypic coefficient of variation (GCV) and phenotypic coefficient of variation (PCV) coupled with high heritability and high genetic advance as a percentage of mean were recorded in all three characters indicating additive gene action. This indicates that there was a low environmental influence on the expression of these characters and hence one can practice selection. The results of this study provide vital information on amylose content gel consistency and gelatinization temperature of various rice landraces which can be utilized in a breeding programme directed towards improving the cooking and eating quality. Landraces with high amylose content can be further studied for identifying landraces with high resistant starch and low Glycaemic Index. Key words: Amylose content, Gel consistency, Gelatinization temperature, landraces, rice

Comparing texture and digestion properties between white and brown rice of indica cultivars preferred by Chinese consumers

The consumption of good tasting rice, mainly soft-textured white rice with low amylose content, has substantially increased in China as living standards improve. However, this diet change may increase the risk of developing type II diabetes because the soft-textured white rice is generally less resistant to digestion and has a higher glycemic index. In contrast, intake of brown rice is inversely associated with type II diabetes risk. This study was conducted to test the possibility that brown rice processed from soft-textured cultivars has both acceptable texture and improved health benefits. Texture and digestion properties were compared between white and brown rice of five indica cultivars preferred by Chinese consumers. Mean hardness was 33% higher while mean springiness was 5% lower for cooked brown rice than for cooked white rice. As compared to cooked white rice, cooked brown rice had a 41% longer mean active digestion duration but 31% lower mean glucose production rate and 11% lower mean total glucose production from starch digestion. However, the differences in texture and starch digestion properties between cooked brown and white rice were affected by cultivar identity. Brown rice processed from suitable cultivars with both a relatively thinner bran layer and relatively higher grain amylose content met consumer requirements in terms of acceptable texture and improved health benefits.

Effects of irrigation schemes on the components and physicochemical properties of starch in waxy wheat lines

The waxy wheat shows special starch quality due to low amylose content. However, less information is available concerning the physicochemical properties of starch in different waxy wheat under different irrigation. In this study, two wheat near-isogenic lines (NILs) and a normal wheat cultivar were used to investigate the contents, size distribution and crystallinity of starch by biochemical methods, laser-diffraction and X-ray diffraction analysis. The amylose content in wheat grains was the lowest in waxy wheat lines, SJZ8-N, followed by the partly waxy wheat lines, SJZ8-P, and the highest in the normal wheat, SJZ8, with significant differences among wheat lines. Waxy wheat starch had more B-type granules and a higher degree of crystallinity than normal wheat starch, with the order as SJZ8-N &amp;gt; SJZ8-P &amp;gt; SJZ8. When compared with the conventional and water-saving irrigation, the rainfed treatment showed the lowest starch content, amylose content (except SJZ8-N), amylopectin content and relative crystallinity in the three wheat lines indicating that water deficiency was not benefited starch accumulation and crystal formation in wheat grains. It was concluded that (1) wheat lines not only differed in amylose content but also in size distribution and crystallinity of starch; (2) irrigation markedly influenced the physicochemical characteristics of wheat starch; therefore, the irrigation schemes could be adjusted to achieve high-quality wheat production.

低アミロース遺伝子“Wx-mq”を有する品種の早晩性の違いが理化学性に与える影響

低アミロース遺伝子“Wx-mq”を有する品種の早晩性の違いが理化学性に与える影響

Evaluation of the Obesity Prevention, Blood Glucose, and Blood Lipid Control of Vietnamese Rice Varieties in High-Fat Diet-Induced Obese Mice.

Five Vietnamese rice varieties, which differ in their basic chemical composition (starch content, amylose content, fiber content) including polished rices and whole grain rices, were chosen for this study. High-fat diet-induced obesity, using these rice, was subjected to in vivo experiments to evaluate the effects of body weight gain, caloric intake, postprandial blood glucose level (PBGL), and glycemic index (GI) in tested mice groups. PBGL peaks appeared at 30th minute after eating, and GI of each experimental group was ranked in order as GN > TL > HR > GM > LĐ and GN > LT > HR > LĐ > GM, respectively, in which, brown rice (LĐ) and germinated brown rice (GM) had low GI. Furthermore, these rice varieties caused the lowest LDL cholesterol and the ratio of LDL/HDL cholesterols in mice. In this study, the higher the amylose and fiber contents were, the lower glycemic index, triglycerides, LDL, and LDL/HDL values were. The golden flower glutinous rice (GN), with low amylose and fiber content, gave worse blood lipid parameters than that of GM and LĐ. Histopathological studies of white adipose and liver tissues showed that LĐ and GM significantly reduced the symptoms of obesity and fatty liver compared with the others, especially compared to GN. The results obtained from this study help patients with overweight, obesity, and type 2 diabetes choose the right rice variety for their daily diet to be able to control their diseases.

Morphological and Molecular Analysis of some Cooking and Eating Quality Traits in rice (Oryza sativa L.) Using Ssr Markers

Two experiments were conducted to evaluate the morphological and molecular variations of grain quality among nineteen rice genotypes, planted during 2019 and 2020 seasons at Rice Research Department,Sakha,Kafrelsheikh, Field Crops Research Institute, Giza, Egypt. From the QTL maps, RM 190 and RM 314 are two SSR markers that have been developed. Based on morphological and molecular levels, there was a significant level of polymorphism. Using the RM190 primer, PCR amplification produced two distinct alleles.Both alleles had a base pair of 100-150. (bp). All tested rice varieties had two alleles A or B, except the Egyptian Yasmine and Giza 181. Rice cultivars with a low presence of allele ‘B’ whose amylose content (AC) values were in intermediate-range also amplified allele ‘B’ exceptionally. Allele ‘A' was present in all other intermediate and high AC rice cultivars. The pooled amylose categories were compared using the Mann-Whitney test to detect if there was a significant relationship between genotype produced by marker RM190 and AC values. As a consequence, RM190could significantly distinguish low AC rice cultivars from intermediate and high AC rice varieties. RM 314 was used to genotype the samples. The marker RM314 amplified two alleles with molecular size 118 and 124 respectively. The first allele (118) this allele could be used to detect the high and low GT but it was not effective for varieties with intermediate GT .

Breeding Novel Short Grain Rice for Tropical Region to Combine Important Agronomical Traits, Biotic Stress Resistance and Cooking Quality in Koshihikari Background

Breeding program strategies to develop novel short grain white rice varieties such as japonica (short grain) that introgress biotic stress resistance and high grain quality have been developed using indica rice (Pin Kaset+4 and Riceberry) for applications in japonica rice (Koshihikari) improvement. Four breeding lines showing promising agronomic performance with short grain and low amylose content (< 20%) were obtained. In addition, sensory testing of these breeding lines showed high scores that similar to Koshihikari. Two promising lines, KP48-1-5 and KP48-1-9, which possessed a combination of four genes resistance to different biotic stresses (Bph3+TPS+Xa21+Pi-ta) and four genes for grain quality (GS3+SSIIa+wxb+badh2), were developed using marker-assisted selection (MAS) with the pedigree method. The current study clearly illustrated the successful use of MAS in combining resistance to multiple biotic stresses while maintaining a high yield potential and preferred grain quality. Moreover, the results indicated that this breeding program, which includes crossing temperatejaponica with indica, can create novel short grain rice varieties adapted to a tropical environment, like the japonica type.

Comparative study on physicochemical properties of starch films prepared from five sweet potato (Ipomoea batatas) cultivars

Five different sweet potato (Ipomoea batatas) cultivars (Daeyumi, Gogeonmi, Sincheonmi [SCM], Singeonmi, and Sinyulmi [SYM]) were used to extract sweet potato starch (SPS) for developing starch-based films. After the chemical composition and amylose contents of all SPSs were evaluated, the morphological, moisture, mechanical, and barrier properties of the SPS-based films were investigated. As one of the film characteristics, the X-ray diffractograms revealed that the SCM-based film with the highest amylose content (26.34%) had the highest relative crystallinity (24.31%). The SCM-based film also showed higher tensile strength (3.05-fold) and elastic modulus (2.38-fold) than the SYM-based film with the lowest amylose content (21.84%). The water vapor and oxygen permeabilities of the SPS-based films were negatively correlated with the amylose content. Thus, the SCM-based film was less permeable for water vapor (3.16-fold) and oxygen (1.81-fold) than the SYM-based film. These results demonstrated that the sweet potato cultivar, especially the amylose content, plays a significant role in determining the physicochemical properties of the SPS-based films.

The assisting effects of ultrasound on the multiscale characteristics of heat-moisture treated starch from Agriophyllum squarrosum seeds

Present study was aimed to characterize the effects of heat-moisture treatments supported by ultrasound on structural, physicochemical and digestive properties of the starch from Agriophyllum squarrosum seeds. The starch sample was subjected to heat-moisture (120°C, 25% moisture) for different durations with assisting by pre- or post-treatment of ultrasound (20 Hz, 300 W, 20 min). A. squarrosum starch exhibited the original A-type of crystalline structure after all treatments. All modified starches had lower amylose content, amylopectin molecular weight, swelling power and solubility, and higher resistant starch content than the native starch. Heat-moisture treatments and dual modifications of heat-moisture and ultrasound increased the gelatinization temperature of starch granules and significantly (p ≤ 0.05) reduced the viscosity of starch paste. Pretreatment of ultrasound enhanced the effects of heat-moisture on the viscosity properties while post-treatment of ultrasound weakened which on the gelatinization temperature, by regulating the changes of double helix structure and short-range ordered structure in starch granules tested by Fourier-transform infrared spectrometer. Scanning electron microscopy unveiled that A. squarrosum starch pretreated by ultrasound became more susceptible to heat moisture in morphology. This work was very important for the deep excavation of the characteristics of A. squarrosum starch and the effective application of ultrasound in starch modifications.

Comparison of the Grain Quality and Starch Physicochemical Properties between Japonica Rice Cultivars with Different Contents of Amylose, as Affected by Nitrogen Fertilization

In order to determine the effects of nitrogen fertilizer on the grain quality and starch physicochemical properties of japonica rice cultivars with different contents of amylose, normal amylose content (NAC) and low amylose content (LAC) cultivars were grown in a field, with or without nitrogen fertilizer (WN). The relationships between the amylose content, starch physicochemical properties and eating quality were also examined. Compared with WN, nitrogen fertilizer (NF) significantly increased the grain yield but markedly decreased the grain weight. In addition, the processing quality tended to improve, but the appearance quality and eating quality deteriorated under NF application. The grain yield was similar between NAC and LAC cultivars. However, the grain quality and starch physicochemical properties were significantly different between NAC and LAC cultivars. The palatability of the cooked rice was significantly higher in the LAC than in NAC cultivar, which was due to its lower amylose content, protein content, hardness, and retrogradation enthalpy and degree, and its higher stickiness, peak viscosity, breakdown, relative crystallinity and peak intensity. The amylose content and protein content were significantly negatively correlated with the palatability. The amylose content was significantly positively correlated with the final viscosity and setback, and was significantly negatively correlated with the relative crystallinity, peak intensity, gelatinization enthalpy and breakdown. Palatability was significantly positively correlated with peak viscosity, breakdown and peak intensity, and was significantly negatively correlated with the final viscosity, setback, and retrogradation enthalpy and degree. Therefore, the selection of a low amylose content japonica rice cultivar grown without nitrogen fertilizer can reduce the amylose and protein contents, as well as improving the pasting properties, starch retrogradation properties and eating quality of the cooked rice.

Comparison of grain yield and quality of different types of japonica rice cultivars in the northern Jiangsu plain, China

In recent years, an increasing number of different types of japonica rice cultivars have been released in the southern rice region of China. The grain yield and quality of these new cultivars showed significant differences in large scale planting. However, the causes of the differences remain little known. Therefore, three typical types of japonica rice cultivars were used in this study to investigate their grain yield and quality. A scanning calorimeter (DSC), X-ray powder diffractometer (XRD), rapid viscosity analyzer (RVA) and taste analyzer were used to evaluate the cooking and eating properties. The results showed that the yield of non-soft hybrid japonica rice cultivars was significantly higher than that of non-soft inbred japonica rice cultivars and soft inbred japonica rice cultivars. Soft inbred japonica rice cultivars had a low amylose content and moderate protein content, which are the main reasons for the superior cooking and eating quality. In addition, the relative crystallinity of soft inbred japonica rice cultivars was significantly higher than that of non-soft inbred and non-soft hybrid japonica rice cultivars, which is considered the major factor resulting in higher transition temperature and gelatinization enthalpy (ΔHgel). Non-soft hybrid japonica rice cultivars had a higher number of large starch granules than soft inbred and non-soft inbred japonica rice cultivars. The setback value (SB) and breakdown value (BD), indirectly reflecting the cooking and eating quality of the three types of japonica rice cultivars, also confirmed that soft inbred japonica rice cultivars with a low SB value and a high BD value had better palatability than the other two types. This study provides guidance for future plantation of different types of japonica rice cultivars in large rice-producing areas.

Impact of extraction methods and genotypes on the properties of starch from peach palm (Bactris gasipaes Kunth) fruits

The aim of this work was to evaluate the effect of starch extraction method of different genotypes of peach palm (Bactris gasipaes Kunth) fruits. Microcarpa, mesocarpa and macrocarpa peach palm fruits contain 77.29, 81.51 and 80.62 g 100 g−1 (dry basis) of starch. Starches extracted by aqueous and alkaline processes presented total starch content above 85%. There is a significant difference between genotypes and extraction process, with starch yield: macrocarpa > mesocarpa > microcarpa for both processes, with alkaline extraction significantly superior. Starch from microcarpa showed the highest resistant starch content. Regardless of genotypes and extraction process, all starches have low amylose content (≤3.99 g 100 g−1), thus classified as waxy starch. The granule size of peach palm starch was around 2–10 μm. Different genotypes of peach palm fruit, starch aqueous and alkaline extraction process, can have a significant effect on decision about peach palm fruit as starch raw material with properties for pharmaceutical, chemical and food applications. Although alkaline extraction has resulted in higher yields, for environmental and chemical properties for food industry, aqueous extraction may be viable, always considering that macrocarpa has stood out as the largest source of starch.

Unearthed New Indel in the Waxy Gene in Glutinous Rice Landraces from Thailand.

&lt;b&gt;Background and Objective:&lt;/b&gt; Glutinous rice landraces have played important role in northeastern and northern region of Thailand and the Lao People's Democratic Republic (PDR) by ethnic groups in this area, both as staple food and ritual in rice culture since ancient times. At a present number of these rice, cultivars have decreased and disappeared from villages without considerations and/or explore DNA variation. This study compared target DNA sequences of &lt;i&gt;waxy&lt;/i&gt; genes of a collection of glutinous rice landraces both upland and lowland rice. &lt;b&gt;Materials and Methods:&lt;/b&gt; A collection of 50 glutinous rice landraces was explored DNA variation in the &lt;i&gt;Waxy&lt;/i&gt; gene by re-sequencing DNA of the two segments (i.e., promoter, exon1 and intron1) of a gene. &lt;b&gt;Results:&lt;/b&gt; New InDel of two deletion G at position 11 (GG-) and C at position 15 (CC-) were observed in DNA sequences of the promoter region and 5'untranslalted region of both upland and lowland rice accessions. Further, the (CT)&lt;sub&gt;17&lt;/sub&gt; and (CT)&lt;sub&gt;18&lt;/sub&gt; were two alleles in these glutinous rice landraces from northern and northeastern Thailand. All glutinous rice landraces exhibited a characteristic of low amylose content or glutinous rice: T Single Nucleotide Polymorphisms (SNP) (AGTTATA) in the first intron splice site. &lt;b&gt;Conclusion:&lt;/b&gt; New InDel in DNA sequences of the promoter region of the &lt;i&gt;waxy&lt;/i&gt; gene in glutinous rice landraces was first reported. This implies that it may reflect the status of genetic background in glutinous rice landraces in Thailand.

The Distribution of Mineral Elements and Protein in Soft Rice was Determined and Analyzed by SEM-EDS Technology

Soft rice is a kind of high-quality rice between glutinous rice and sticky rice. It has low amylose content, crystal clear grains, sweet taste, soft glutinous, and is suitable for cooking and porridge. Chalkiness in soft rice is a white opaque part formed by loose endosperm. It is an important character that affects the appearance quality, processing, and cooking quality of rice, and also an important limiting factor that restricts the standard rate of high-quality rice in China. The combination of scanning electron microscope and energy dispersive spectrometer (SEM-EDS) can be used for in-depth analysis of rice, visualization, and quantitative analysis of element distribution in rice. The results showed that there were many kinds of mineral elements in soft rice seeds, among which C and O were the most abundant, followed by N and P, and Mg, Al, P, S, K, Ca, Mn, and Zn were less. The contents of C, N, P, and S in the non-chalky area were significantly higher than those in the chalky area. Especially N and S were the best indicators of protein, and the contents in the chalky area were higher than those in the non-chalky area. It means that the protein content in the chalky part of soft rice seed is less than that in the non-chalky part, which affects the nutritional quality of soft rice. Therefore, the results of this study laid a solid foundation for the in-depth analysis of the distribution of mineral elements and protein in soft rice and their effects on the quality of soft rice, which also provided important information for the cultivation of new high-quality rice varieties in the future.

Characterizing the impact of high temperature during grain filling on phytohormone levels, enzyme activity and metabolic profiles of an early indica rice variety.

Global warming results in high temperature stress (HTS), which presents severe challenges worldwide for modern agricultural production and will have significant impacts on the yield and quality of crops. Accumulation of photosynthetic products, activity of enzymes involved in sucrose-starch metabolism, phytohormone levels and metabolic profiling using LC-MS were analysed in the flag leaves and/or developing grains subjected to HTS during the grain-filling stage of an indica rice. HTS induced significant yield loss and reduced the grain quality, with lower amylose content. HTS reduced photosynthetic product accumulation in flag leaves and reduced starch accumulation in developing grains, compared to growth under normal temperatures. The activity of enzymes related to sucrose-starch metabolism were dis-regulated in developing grains grown under high temperature (HT). Moreover, phytohormone homeostasis in flag leaves and developing grains was also dramatically disturbed by HT. Metabolic profiling detected many metabolites with remarkably different relative fold abundances at different time points in the developing grain at HT versus normal temperatures, these metabolites were enriched in several HTS response pathways. The change in phytohormone ratio and auxin level might be associated with the reduction in photosynthetic products and their translocation, and ultimately with reduced starch accumulation in the developing grain. The detected metabolites might have different roles in response to the HTS in developing grain at different development stages. These results provide a theoretical reference and basis for future rice production towards higher quality and yield when grown under HTS.