Changes in Activities of the Key Enzymes Related to Starch Synthesis in Rice Grains During Grain Filling and Their Relationships with the Filling Rate and Cooking Quality

With 10 rice cultivars (lines) as materials, the changes in activities of adenosine diphosphoglucose pyrophosphorylase(ADPGPase), starch synthase (SSase) and starch branching enzyme (Q-enzyme) in the grains during grain filling, and theirrelationships with the filling rate, gel consistency (GC), alkali spreading value (ASV) and amylose content (AC) werestudied. The results showed that changes in activities of ADPGPase, SSase and Q-enzyme exhibited a single peak duringgrain filling, and the time of the activity peaks for the former two enzymes was earlier than that of the maximum grain-fillingrate (Tmax), and the time reaching the peak for Q-enzyme was synchronous with Tmax. The activities at early grain fillingstage, and the mean and maximum activities of each enzyme during grain filling period were positively and significantly orvery significantly correlated with the mean and maximum grain filling rate and starch content (mg grain-1) in the grains.Activities of ADPGPase at all grain filling stages and those of Q-enzyme at the early and mid filling stages were notsignificantly correlated the cooking quality (GC, ASV and AC). SSase activities at the early filling stage were significantlyand negatively correlated with GC and ASV, and positively correlated with AC. Activities of SSase at mid and late grainfilling stages and Q-enzyme at the late filling stage were significantly and positively correlated with GC and ASV, andnegatively correlated with AC. Spraying zeatin or abscisic acid at early grain filling stage could obviously regulate theactivities of ADPGPase, SSase and Q-enzyme in the grains.

Low Light During Grain Filling Stage Deteriorates Rice Cooking Quality, but not Nutritional Value

To investigate the effect of low light （LL, 50% natural light） during grain filling （GF） stage on rice transamination, amino acid （AA） accumulation, nutritional value, and cooking quality in three different rice genotypes, transaminase activities and AA levels in grains during GF stage and the traits that significantly affected rice quality （physical appearance, cooking quality, and nutritional value） were analyzed. LL did not disturb transamination in rice grains during GF stage, as minimal impact was found on alanine and aspartate transaminase activities. Nevertheless, most AAs in caryopses, including lysine and threonine, increased in response to LL, except for sulfur-containing AAs. These results suggest that AA metabolism and accumulation in rice grains were rarely suppressed by LL during GF stage. Rice nutritional ingredients at harvest, such as major protein components including glutelin and most important essential amino acids （EAAs） including lysine and threonine, increased significantly in response to LL, whereas most protein and EAA ratios were rarely affected. However, LL markedly affected physical appearance of rice grains by reducing brown rice rate, milled rice rate, and 1000-grain weight and increasing the chalkiness rate. In addition, cooking qualities decreased in response to LL, while breakdown values and amylose levels decreased and setback values increased. We concluded that LL during GF stage decreased the cooking quality of rice, but could potentially improve the nutritional value of rice.

Analysis of seed and maternal genetic effects on cooking quality characters in indica hybrid rice

We analysed seed and maternal genetic effects on characters of cooking quality in indica hybrid rice by using the model for quantitative characters of seeds of cereal crops. Incomplete diallel crosses were made by using six male sterile lines (Zhenshan 97A, Erjiuqing A, Erjiunan 1A, V20A, Zhe’nan 1A and Zhe’nan 3A)as females and three restorer lines(Cezao 2-2, T49 and 26715)as males. Sampled seeds were used to measure the cooking quality characters, including amylose content(%), gelatinization temperature(alkali spreading score)and gel consistency(mm). Results indicated that some rice cooking quality characters were controlled by both seed genes and maternal genes (see table). Gel consistency was mainly controlled by maternal effects, but also

A rare Waxy allele coordinately improves rice eating and cooking quality and grain transparency

In rice(Oryza sativa), amylose content(AC) is the major factor that determines eating and cooking quality(ECQ). The diversity in AC is largely attributed to natural allelic variation at the Waxy(Wx)locus. Here we identified a rare Wx allele, Wx^(mw) ,which combines a favorable AC, improved ECQ and grain transparency. Based on a phylogenetic analysis of Wx genomic sequences from 370 rice accessions, we speculated that Wx^(mw) may have derived from recombination between two important natural Wx alleles, Wx^(in) and Wx^(b). We validated the effects of Wx^(mw) on rice grain quality using both transgenic lines and near-isogenic lines(NILs). When introgressed into the japonica Nipponbare(NIP) background, Wx^(mw) resulted in a moderate AC that was intermediate between that of NILs carrying the Wx^(b)allele and NILs with the Wx^(mp) allele. Notably, mature grains of NILs fixed for Wx^(mw) had an improved transparent endosperm relative to soft rice. Further, we introduced Wx^(mw) into a high-yielding japonica cultivar via molecular marker-assisted selection: the introgressed lines exhibited clear improvements in ECQ and endosperm transparency. Our results suggest that Wx^(mw) is a promising allele to improve grain quality, especially ECQ and grain transparency of high-yielding japonica cultivars, in rice breeding programs.

Relationship Between Variation in Activities of Key Enzymes Related to Starch Synthesis During Grain Filling Period and Quality of Eating and Cooking in Rice

Four japonica rice varieties with significant differences in quality of eating and cooking were used in the experiment. The varieties showed differences in amylose and amylopectin contents at different grain filling stages, which were attributed to the accumulative speed of starch at different grain filling stages. During grain filling period, the varieties had no difference in the time when the activities of ADPglocose pyrophosphorylase （AGPP） and soluble starch synthesis （SSS） reached a maximum, but had difference in the time when the activity of starch branching enzyme （SBE） reached a maximum, in which the inferior quality varieties were earlier than the high quality ones, and high quality varieties still kept high enzyme activities at the late stage of grain filling. The correlation and correlative degree between AGPP, SSS, SBE and amylose content, amylopectin content, taste meter value, and RVA properties varied with the different stages of grain filling. The correlation between SSS activity and taste meter value was not significant during the whole period of grain filling, but the activities of AGPP and SBE had significant or highly significant correlation with taste meter value. It was helpful for improving quality of eating and cooking of japonica rice to use the materials with low enzyme activity at the early stage of grain filling or high enzyme activity at the late stage as parents.

Optimization of enzymatic hydrolysis of pigeon pea for cooking quality of dhal

Cooking quality of dehusked splits is influenced by the dehulling method,in particular,by the pre-milling treatments.The effects of four enzymatic hydrolysis parameters,i.e.,enzyme concentration(20-60 mg/100 g dry matter),incubation time(3-15 h),incubation temperature(40-60℃)and tempering water pH(4.0-6.0)on cooking time of pigeon pea dhal were optimized using response surface methodology.Three kinds of enzymes,i.e.,xylanase,pectinase,and cellulas were used in combination for enzymatic pre-treatment.A quadratic model satisfactorily described the dehulling efficiency with high value for the coefficient of determination R^(2)(0.9062).It predicted a minimum cooking time of 21.91 min at enzyme concentration of 37.8 mg/100 g dry matter,incubation time 8.69 min,incubation temperature 48.5℃ and pH 5.49 of tempering water.Cooking time at optimum condition was observed to be 21.50 min and the predicted values of cooking time showed 2.19% deviation from the experimental values.Results of the study revealed that cooking time of enzyme treated dhal could be decreased by 19.77% compared to the oil treated dhal.

Rapid improvement of rice eating and cooking quality through gene editing toward glutelin as target

Rice eating and cooking quality(ECQ)is a major concern of breeders and consumers,determining market competitiveness worldwide.Rice grain protein content(GPC)is negatively related to ECQ,making it possible to improve ECQ by manipulating GPC.However,GPC is genetically complex and sensitive to environmental conditions;therefore,little progress has been made in traditional breeding for ECQ.Here,we report that CRISPR/Cas9-mediated knockout of genes encoding the grain storage protein glutelin rapidly produced lines with downregulated GPC and improved ECQ.Our finding provides a new strategy for improving rice ECQ.

Changes in Cooking and Nutrition Qualities of Grains at Different Positions in a Rice Panicle under Different Nitrogen Levels

Cooking and nutrition qualities of grain are two of the most important aspects of rice quality. To understand the difference in cooking and nutrition qualities among the grains at different positions within a rice panicle, the distributions of gel consistency （GC）, amylose content （AC） and crude protein content （CPC） of grains in a panicle in association with different nitrogen levels （0, 120 and 240 k c/ha） were investigated by using two rice varieties, Yangdao 6 （indica） and Wuyujing 3 （japonica）. In general, the grains at the basal part of a panicle had lower GC and higher AC than those at the upper or middle part of a panicle. The 1^st grain on the secondary branch with earlier flowering exhibited the highest GC, whereas the 2nd grain on the primary branch with later flowering showed the highest AC. For Yangdao 6, CPC in the grains on the primary branches was lower at the middle part of a panicle than at the upper or basal part of a panicle. For Wuyujing 3, there were no significant differences in CPCs in the grains among the upper, middle and basal parts of a panicle. GC in the grains was increased, whereas AC was reduced from zero nitrogen application （ON） to low amount of nitrogen application （LN）, and the result was reversed from LN to medium amount of nitrogen application （MN）. CPC was increased with the increase in the amount of nitrogen application.

Correlation of Plant Morphological and Grain Quality Traits with Mineral Element Contents in Yunnan Rice

Correlations between four grain quality, 24 plant morphological traits and eight element contents of 653 accessions from Yunnan rice were analyzed. P, K, Ca and Mg contents of core collection were closely correlated to the most plant morphological and grain quality traits, and there were highly significant correlations （P 〈0.01） among some traits including P content to number of stems and tillers, K content and amylose content, Ca content and plant height, Mg content and protein content. Mn, Zn, Cu and Fe contents of core collection were closely related to a few traits, such as Fe content and gel consistency （-0.1121^＊＊）, Zn content and seed setting rate （-0.1411^＊＊）, Cu content and number of grains per panicle （-0.1398^＊＊）, Mn content and plant height （-0.2492^＊＊）.

Effect of Temperature at Grain Filling Stage on Activities of Key Enzymes Related to Starch Synthesis and Grain Quality of Rice

Three japonica rice varieties with different cooking and eating quality were grown at high temperature in the greenhouse and natural field. Effects of temperature at the grain filling stage on these varieties were investigated in terms of the activities of key enzymes related to starch synthesis and cooking and eating quality of rice grain. The high temperature at the grain filling stage increased protein content, and decreased amylose content and taste meter value of rice; inferior grain quality varieties showed a greater magnitude of the increase or decrease than the superior ones. Reaction of rapid visco analyser profiles to the temperature varied with rice varieties. The activities of adenosine diphosphoglucose pyrophosphoryiase （AGPP）, soluble starch synthase （SSS） and starch branching enzyme （SBE） gradually increased to a peak value, and thereafter declined as grain filling progressed. Enzyme activities in different varieties differed in a same filling stage, and also in the time when the enzyme activity reached a maximum. AGPP and SSS were insensitive to the environmental temperature, but SBE was comparatively sensitive to the temperature, and its activity declined when temperature was too high or too low.

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(ΔH_(gel)).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.

Genome-Wide Association Study of Cooked Rice Textural Attributes and Starch Physicochemical Properties in indica Rice

Rice cooking and eating qualities(CEQ)are mainly determined by cooked rice textural parameters and starch physicochemical properties.However,the genetic bases of grain texture and starch properties in rice have not been fully understood.We conducted a genome-wide association study for apparent amylose content(AAC),starch pasting viscosities,and cooked rice textural parameters using 279 indica rice accessions from the 3000 Rice Genome Project.We identified 26 QTLs in the whole population and detected single nucleotide polymorphisms(SNPs)with the lowest P-value at the Waxy(Wx)locus for all traits except pasting temperature and cohesiveness.Additionally,we detected significant SNPs at the SUBSTANDARD STARCH GRAIN6(SSG6)locus for AAC,setback(SB),hardness,adhesiveness,chewiness(CHEW),gumminess(GUM),and resilience.We subsequently divided the population using a SNP adjacent to the Waxy locus,and identified 23 QTLs and 12 QTLs in two sub-panels,WxT and WxA,respectively.In these sub-panels,SSG6 was also identified to be associated with pasting parameters,including peak viscosity,hot paste viscosity,cold paste viscosity,and consistency viscosity.Furthermore,a candidate gene encoding monosaccharide transporter 5(OsMST5)was identified to be associated with AAC,breakdown,SB,CHEW,and GUM.In total,39 QTLs were co-localized with known genes or previously reported QTLs.These identified genes and QTLs provide valuable information for genetic manipulation to improve rice CEQ.

Effects of Chalkiness on Cooking,Eating and Nutritional Qualities of Rice in Two indica Varieties

An experiment was conducted to investigate the effects of chalkiness on cooking, eating and nutrition qualities of rice using Gangyou 527 （indica hybrid rice） and Zhaiyeqing 8 （conventional indica rice） as materials. Compared with the milled rice without chalkiness, amylose content, final viscosity, setback and consistence increased significantly, while gel consistence, peak viscosity and breakdown decreased remarkably and other RVA values did not have significant changes in the chalky rice of Gangyou 527. The differences in the above indices between the chalky and non-chalky rice was not remarkable in Zhaiyeqing 8. The crude protein content of chalky rice in Zhaiyeqing 8 was significantly lower than that of non-chalky rice, but there was no remarkable change between the chalky and non-chalky rice in Gangyou 527. Glutelin content fell significantly, and albumin, globulin, prolamine and lysine contents did not change significantly in chalky rice compared with non-chalky rice in the two varieties.

Relationship Between Root Chemical Signals and Grain Quality of Rice

This study was designed to elucidate the relationship between root chemical signals and the quality of rice. Various rice genotypes were used. Zeatin （Z） ＋ zeatin riboside （ZR）, abscisic acid （ABA）, 1-aminocylopropane -1-carboxylic acid （ACC）, and organic acids in roots during grain filling and the appearance quality, cooking/eating quality were investigated. The correlations among them were analyzed. The results showed that Z ＋ ZR concentrations in the roots at mid- and lategrain-filling stages were significantly and positively correlated with the gel consistency and alkali spreading value （r = 0.72^＊ - 0.90^＊＊）, whereas negatively correlated with the amylose content （r = -0.68^＊ - -0.78^＊＊）. ABA concentrations in roots at mid- grain-filling stage were significantly and negatively correlated with the gel consistency and alkali spreading value （r = -0.90^＊＊-0.91^＊＊）, and positively correlated with the amylose content （r = 0.87^＊＊）. ACC concentrations in root exudates at mid-grain-filling stage were very significantly correlated with the percentage of chalky grains and chalkiness （r = 0.97^＊＊ - 0.98^＊＊）, and those at late-grain-filling stage Were significantly correlated with chalkiness and chalky size （r = 0.69^＊ - 0.96^＊＊）. The more the malic acid and succinic acid exuded from roots for a cultivar, the greater the breakdown values and the smaller the setback values in the starch profile, and the results were reversed for a cultivar with more tartaric acid and citric acid exuded from roots during the grain-filling period. The cultivar with more lactic acid in exudates had smaller gel consistency and alkali spreading values, but had greater amylose content. When roots were treated with exogenous ZR, ABA, and ACC during grain filling, effects of the chemicals on the rice quality were consistent with the relationships of the endogenous hormones （Z ＋ ZR, ABA, and ACC） with the quality indexes. Using rape cake as organic fertilizer can increase the concentrations of malic acid and succinic acids exuded from roots as well as the breakdown value in starch profile and reduce the setback value. The results suggest that root chemical signals play important roles in the formation of rice quality, and dee quality could be improved through regulating the signals.

Differential expressions among five Waxy alleles and their effects on the eating and cooking qualities in specialty rice cultivars

Eating and cooking qualities（ECQs） of rice are important attributes due to its major influence on consumer acceptability. To better understand the molecular mechanism of the variation in ECQs, we investigated and compared the expressions among different alleles of the Waxy（Wx） gene and its effect on ECQs in specialty rice cultivars. The results showed that the accumulation of amylose was positively and significantly correlated to the level of mature Wx m RNA and granule-bound starch synthase I（GBSS I） in developing rice grain at 12 days after flowering. The amount of GBSS I and its activity together are the main factors controlling amylose synthesis. Differences in ECQs among five Wx allele types were investigated in samples from 15 rice varieties. The apparent amylose content（AAC） and gel consistency（GC） were similar in each type of Wx allele. The AAC followed the order, Wx^a type〉Wx^in type〉Wx^b type〉Wx^mq type〉wx. Contrary to this, the GC showed an opposite trend compared to AAC. There was a wide variation in rapid visco analyzer（RVA） profile among five Wx allele types, while varieties sharing a specified Wx allele had basically the similar RVA profile, although there was a slight difference in some RVA parameters, peak, hot paste and cool paste viscosities.

Effects of High Temperature and Strong Light Combine Stress on Yield and Quality of Early Indica Rice with Different Amylose Content during Grout Filling

High temperature(HT)accompanied with strong light(SL)often occurs in early indica rice production during grout filling stage in Southern China,which accelerates grain ripening.Two indica rice cultivars with different amylose content(Zhongjiazao17,ZJZ17,high amylose content;Xiangzaoxian45,XZX45,low amylose content)were grown under control(CK),HT,and HT+SL conditions during grout filling to determine the effects on grain yield and quality of rice.The results showed that compared with CK,HT and HT+SL significantly reduced the 1000-grain weight and filled grain rate whether in high or low amylose content early indica rice cultivars during grout filling,resulting in a significantly lower grain yield.Meanwhile,HT and HT+SL significantly decreased the milled rice rate,brown rice rate and head rice rate,whereas significantly increased chalky rate and chalky degree;and breakdown decreased and setback,pasting temperature increased in the cultivars,leading to the poor processing,appearance and cooking and eating quality of early indica rice cultivars.Compared with HT,the yield of ZJZ17 was significantly decreased under HT+SL,due to the lower 1000-grain weight.However,the effect of HT+SL on rice quality varied in the cultivars.In general,the yield and rice quality of ZJZ17 were relatively poor under HT+SL.Our results suggested that HT and HT+SL during grout filling had significant damage to the yield and quality of early indica rice cultivars,especially HT+SL,while the high amylose cultivar ZJZ17 showed a higher negative effect under HT+SL.

Global production, processing and utilization of lentil： A review

Lentil is a highly nutritious legume with an ample quantity of carbohydrates and good amount of proteins, minerals, vitamins, phytochemicals and fibres. Although it has been used as staple food since ancient times, its usage has been limited in developed countries, especially due to the lower protein digestibility, presence of anti-nutritional factors, flatulence and poor cooking qualities. Processing of lentils including dehulling and splitting and isolation of major fractions, e.g., proteins and starches are some of the strategies that can be adopted to add value and increase consumption of these legumes. This review paper intends to provide detailed overview of lentil＇s global production, nutritional composition and processing methods of lentil. Methods of isolation/characterization of lentil protein and starch and their subsequent application in foods are also presented.

Mapping quantitative trait loci associated with starch paste viscosity attributes by using double haploid populations of rice (Oryza sativa L.)

The paste viscosity attributes of starch,measured by rapid visco analyzer(RVA),are important factors for the evaluation of the cooking and eating qualities of rice in breeding programs.To determine the genetic roots of the paste viscosity attributes of rice grains,quantitative trait loci(QTLs)associated with the paste viscosity attributes were mapped,using a double haploid(DH)population derived from Zhongjiazao 17(YK17),a super rice variety,crossed with D50,a tropic japonica variety.Fifty-four QTLs,for seven parameters of the RVA profiles,were identified in three planting seasons.The 54 QTLs were located on all of the 12 chromosomes,with a single QTL explaining 5.99 to 47.11%of phenotypic variation.From the QTLs identified,four were repeatedly detected under three environmental conditions and the other four QTLs were repeated under two environments.Most of the QTLs detected for peak viscosity(PKV),trough viscosity(TV),cool paste viscosity(CPV),breakdown viscosity(BDV),setback viscosity(SBV),and peak time(PeT)were located in the interval of RM 6775-RM 3805 under all three environmental conditions,with the exception of pasting temperature(PaT).For digenic interactions,eight QTLs with six traits were identified for additivexenvironment interactions in all three planting environments.The epistatic interactions were estimated only for PKV,SBV and PaT.The present study will facilitate further understanding of the genetic architecture of eating and cooking quality(ECQ)in the rice quality improvement program.

Novel Wx alleles generated by base editing for improvement of rice grain quality

Amylose content(AC),which is regulated by the Waxy(Wx)gene,is a major indicator of eating and cooking quality(ECQ)in rice(Oryza sativa).Thus far,only a limited number of mutations in the N-terminal domain of Wx were found to have a major impact on the AC of rice grains and no mutations with such effects were reported for other regions of the Wx protein.Here,nucleotide substitutions in the middle region of Wx were generated by adenine and cytosine base editors.The nucleotide substitutions led to changes in 15 amino acid residues of Wx,and a series of novel Wx alleles with ACs of 0.3%-29.43%(wild type with AC of 19.87%)were obtained.Importantly,the waxy~(abe2)allele showed a"soft rice"AC,improved ECQ,favorable appearance,and no undesirable agronomic traits.The transgenes were removed from the waxy~(abe2)progeny,generating a promising breeding material for improving rice grain quality.