Short Amylopectin Chains Research Articles

Starch Synthase IIa-Deficient Mutant Rice Line Produces Endosperm Starch With Lower Gelatinization Temperature Than Japonica Rice Cultivars.

The gelatinization temperature of endosperm starch in most japonica rice cultivars is significantly lower than that in most indica rice cultivars. This is because three single nucleotide polymorphisms in the Starch synthase (SS) IIa gene in japonica rice cultivars (SSIIaJ) significantly reduce SSIIa activity, resulting in an increase in amylopectin short chains with degree of polymerization (DP) ≤ 12 compared to indica rice cultivars (SSIIaI). SSIIa forms a trimeric complex with SSI and starch branching enzyme (BE) IIb in maize and japonica rice, which is likely important for the biosynthesis of short and intermediate amylopectin chains (DP ≤ 24) within the amylopectin cluster. It was unknown whether the complete absence of SSIIa further increases amylopectin short chains and reduces gelatinization temperature and/or forms altered protein complexes due to the lack of a suitable mutant. Here, we identify the SSIIa-deficient mutant rice line EM204 (ss2a) from a screen of ca. 1,500 plants of the rice cultivar Kinmaze (japonica) that were subjected to N-methyl-N-nitrosourea mutagenesis. The SSIIa gene in EM204 was mutated at the boundary between intron 5 and exon 6, which generated a guanine to adenine mutation and resulted in deletion of exon 6 in the mRNA transcript. SSIIa activity and SSIIa protein in developing endosperm of EM204 were not detected by native-PAGE/SS activity staining and native-PAGE/immunoblotting, respectively. SSIIa protein was completely absent in mature seeds. Gel filtration chromatography of soluble protein extracted from developing seeds showed that the SSI elution pattern in EM204 was altered and more SSI was eluted around 300 kDa, which corresponds with the molecular weight of trimeric complexes in wild type. The apparent amylose content of EM204 rice grains was higher than that in its parent Kinmaze. EM204 also had higher content of amylopectin short chains (DP ≤ 12) than Kinmaze, which reduced the gelatinization temperature of EM204 starch by 5.6°C compared to Kinmaze. These results indicate that EM204 starch will be suitable for making foods and food additives that easily gelatinize and slowly retrograde.

Pullulanase Debranching of Various Starches Upgrades the Crystalline Structure and Thermostability of Starch‐Lauric Acid Complexes

Cassava, rice, and chickpea starches with different amylose contents and amylopectin structure are used to prepare helical inclusion complexes with lauric acid (LA) and to investigate the effect of pullulanase debranching on complex formation, crystalline structure, thermostability, and morphology compared to their non‐debranched counterparts. The quantity of inclusion complexes in debranched starches increased 2–9 times compared to non‐debranched starches, due to the release of debranched, linear amylopectin chains. The amount of complexes after debranching increased with amylopectin content, and with the proportion of amylopectin short chains. Retrogradation occurred under the same conditions as and in competition with complexation; however, carefully adjusting the conditions enabled minimization of retrogradation and maximization of complex formation.

High-amylose starch as a new ingredient to balance nutrition and texture of food

Starch can provide food (such as cake) with a good texture. However, starch also causes the postprandial glycaemic response, which leads to Type-2 diabetes and cardiovascular diseases. In this study, we developed high-amylose starch as a new ingredient. The molecular structure of high-amylose maize starch (HAMS) was also studied to explore the effects of HAMS on the physicochemical, digestion and texture properties of high-amylose maize flour cakes (HAMFCs). The results showed the small molecular size, low amounts of short amylopectin chains, and high amounts of long amylopectin chains and amylose chains of HAMS are helpful to understand the texture (the increase in hardness, cohesiveness, chewiness and resilience and the decrease in springiness) and digestion (the increase in SDS and RS and the decrease in RDS) properties, and the formation of V-type crystalline structure in HAMFCs. Special molecule structure of HAMS and V-type crystalline are the main reason for the improvement of RS in HAMFCs. Sensory evaluation showed that HAMFCs would be accepted by customers and 20% HAMF addition is the best scheme. In sum, the molecular structure of HAMS helps understand the quality of HAMFCs; and HAMFCs could be developed as novel food with a higher RS and acceptable sensory attributes.

Effects of different Wx alleles on amylopectin molecular structure and enzymatic hydrolysis properties of rice starch

ABSTRACTAllelic variation at the Wx locus plays a vital role in regulating apparent amylose content (AAC) as well as other important starch properties in rice grain. However, the extent of Wx allelic variation affecting amylopectin fine structure and enzymatic hydrolysis properties of rice starch remains unknown. In this paper, a series of rice single-segment substitution lines with five different Wx alleles (wx, Wxt, Wxg1, Wxg2 and Wxg3) were used for comparative studies. The results showed that the five Wx alleles exhibited a wide variation in amylopectin molecular structure, hydrolysis and in vitro digestion properties of rice starch. Amylopectin chain length distribution as evaluated by fluorophore-assisted capillary electrophoresis was significantly different for the five Wx alleles, which might result in different functional properties. The hydrolysis degree of the five Wx genotype starches by α-amylase or amyloglucocidase was in the order wx > Wxt > Wxg1 > Wxg3 > Wxg2. The rapidly digestible starch (RDS) content of the tested rice starches followed the order wx = Wxg3 > Wxt = Wxg1 > Wxg2. The extent decrease of slowly digestible starch (SDS) content was wx = Wxt > Wxg1 > Wxg2 > Wxg3, while the trend in resistant starch (RS) content was Wxg2 > Wxg3 > Wxg1 > Wxt > wx. Correlation analysis indicated that AAC was significantly positively correlated with RS but significantly negatively correlated with SDS and hydrolysis. The RDS showed a significant positive correlation with amylopectin short chains (DP 6–12) but no significant correlations with other structural properties. The present results could provide important information for the application of rice starches with different Wx genotypes.

Structural, Morphological, Thermal, and Pasting Properties of Starches From Diverse Indian Potato Cultivars

Starches from 42 diverse Indian potato cultivars are evaluated for diversity in structural (amylose content and amylopectin chain length distribution), morphological (granules size distribution), thermal, and pasting properties. Amylose content varied between 6.5 and 32.2% while the proportion of short (DP 6–12), medium (DP 13–18), and long (DP 19–30) amylopectin chains varied in the range from 37.2 to 45.4%, 35.6 to 39.1%, and 17.8 to 24.5%, respectively. Starches with higher transition temperature showed lower enthalpy of gelatinization. The proportion of small granules (<10 μm) correlated negatively to short amylopectin chains (DP 6–12), peak viscosity, and breakdown viscosity. Transition and pasting temperature related negatively to the proportion of short and medium chains of amylopectin (DP 6–12 and 13–18, respectively), while positively to that of long chains (DP 19–30). Peak viscosity and breakdown viscosity has a negative relation while the final and setback viscosity have a positive relation with long amylopectin chains.

Gradually Decreasing Starch Branching Enzyme Expression Is Responsible for the Formation of Heterogeneous Starch Granules.

Rice (Oryza sativa) endosperm is mainly occupied by homogeneous polygonal starch from inside to outside. However, morphologically different (heterogeneous) starches have been identified in some rice mutants. How these heterogeneous starches form remains unknown. A high-amylose rice line (TRS) generated through the antisense inhibition of starch branching synthase I (SBEI) and SBEIIb contains four heterogeneous starches: polygonal, aggregate, elongated, and hollow starch; these starches are regionally distributed in the endosperm from inside to outside. Here, we investigated the relationship between SBE dosage and the morphological architecture of heterogeneous starches in TRS endosperm from the view of the molecular structure of starch. The results indicated that their molecular structures underwent regular changes, including gradually increasing true amylose content but decreasing amylopectin content and gradually increasing the ratio of amylopectin long chain but decreasing the ratio of amylopectin short chain. Granule-bound starch synthase I (GBSSI) amounts in the four heterogeneous starches were not significantly different from each other, but SBEI, SBEIIa, and SBEIIb showed a gradually decreasing trend. Further immunostaining analysis revealed that the gradually decreasing SBEs acting on the formation of the four heterogeneous granules were mainly due to the spatial distribution of the three SBEs in the endosperm. It was suggested that the decreased amylopectin in starch might remove steric hindrance and provide extra space for abundant amylose accumulation when the GBSSI amount was not elevated. Furthermore, extra amylose coupled with altered amylopectin structure possibly led to morphological changes in heterogeneous granules.

Biosynthesis of waxy starch - a review

Starch comprises nearly linear amylose and branched amylopectin, whilst waxy starches are a special form, containing almost exclusively amylopectin. Modern techniques in plant breeding together with new data from starch biosynthesis research have enabled new food and non-food uses of waxy starches. This paper describes the basic ways of glucose conversion to waxy starch in plants. The recent evidence of ADP-Glc accumulation in cytosol of photosynthetically competent cells proposes a more complex pathway of starch biosynthesis based on a tight interconnection of sucrose and starch metabolic pathways. Also many studies indicate the existence of different pathways for the sucrose-starch conversion process in heterotrophic organs of dicotyledonous and monocotyledonous plants. At least six classes of starch synthases (SS) have been recognised in plants including soluble SS1, SS2, SS3, SS4, SS5, and granule bound SS (GBSS), required for the synthesis of short and long chains of amylopectin, till now. As to amylose (not-present in waxy starches), GBSS is the only starch synthase isoform encoded by the waxy genes situated at independent loci.

Molecular structures and properties of starches of Australian wild rice

Australian wild rices have significant genetic differences from domesticated rices, which might provide rices with different starch molecular structure and thus different functional properties. Molecular structure, gelatinization properties, and pasting behaviours of starch of three Australian wild rices (Oryza australiensis, taxa A (O. rufipogon like) and taxa B (O. meridionalis like)) were determined and compared to domesticated indica and japonica rice. These had higher amylose content, more shorter amylose chains and fewer short amylopectin chains, resulted in a high gelatinization temperature in these wild rices. Compared to domesticated japonica rice, taxa A had a lower pasting viscosity; taxa B had a similar pasting viscosity but lower final viscosity. The significantly different starch molecular structure from that of normal domesticated rices, and concomitantly different properties, suggest advantageous uses in products such as rice crackers or rice pudding, and a source of nutritionally-desirable slowly digestible starch.

Dough rheological properties and noodle-making performance of non-waxy and waxy whole-wheat flour blends

Dough rheological properties and noodle-making performance of non-waxy whole-wheat flour (WWF) with partial- or full-waxy (PW- or FW-) WWF substitution were studied. The substitution levels were 0, 250, 500, 750, and 1000 g/kg, respectively. FW-WWF reduced the peak viscosity and pasting temperature of WWF blends as its substitution level was increased due to its higher proportions of B-type starch granules and short amylopectin chains, while PW-WWF increased peak viscosity with the increasing substitution level because of its higher amylopectin content. As demonstrated by farinograph and rheometer measurements, FW-WWF interfered with gluten development because of the increased competition for water by arabinoxylans and amylopectin; however, PW-WWF enhanced dough strength due primarily to its increased protein content. Consequently, FW-WWF showed a detrimental effect on cooked noodle texture as the cooked noodle hardness was reduced by 50% at the 1000 g/kg substitution level. In contrast, PW-WWF enhanced noodle integrity and elasticity by increasing cooked noodle cohesiveness and resilience by 10.1% and 14.8%, respectively, at the 1000 g/kg substitution level. The results suggest that with waxy WWF substitution, the changes in starch composition, arabinoxylans, and protein content could modify the interactions among flour components and influence the quality characteristics of noodle products.

Effect of microwave irradiation on internal molecular structure and physical properties of waxy maize starch

Native waxy maize starch was treated at a moisture content of 30% by microwave irradiation for 5 min, 10 min and 20 min, respectively. The molecular structure and physical properties of waxy maize starch were characterized. Compared with native maize starch, lower population of short chains of amylopectin (A chain), higher proportion of short B1 and long B2 and B3 were observed in irradiated starches. 1H NMR data showed that α-(1,6) glycosidic linkages were destroyed more easily than α-(1,4) glycosidic linkages during microwave treatment. A increase in gelatinization temperatures and a decrease in the molecular weight, the relative crystallinity, ΔH, viscosities and syneresis were observed after microwave treatment. Gelatinization temperatures were positively correlated with long chains B3 with DP > 36, while ΔH and syneresis were negatively correlated with them. The extent of the changes induced by microwave treatment for different times revealed that the major degradation occurred in internal chain (amorphous region) at the first stage (microwave treatment for 5 min), the external chain (crystalline region) mostly destroyed at the second stage (microwave treatment for above 10 min). The foregoing data indicated that the molecular structure of amylopectin is a critical factor determining physical properties.

The molecular structural features controlling stickiness in cooked rice, a major palatability determinant

The stickiness of cooked rice is important for eating quality and consumer acceptance. The first molecular understanding of stickiness is obtained from leaching and molecular structural characteristics during cooking. Starch is a highly branched glucose polymer. We find (i) the molecular size of leached amylopectin is 30 times smaller than that of native amylopectin while (ii) that of leached amylose is 5 times smaller than that of native amylose, (iii) the chain-length distribution (CLD: the number of monomer units in a chain on the branched polymer) of leached amylopectin is similar to native amylopectin while (iv) the CLD of leached amylose is much narrower than that of the native amylose, and (v) mainly amylopectin, not amylose, leaches out of the granule and rice kernel during cooking. Stickiness is found to increase with decreasing amylose content in the whole grain, and, in the leachate, with increasing total amount of amylopectin, the proportion of short amylopectin chains, and amylopectin molecular size. Molecular adhesion mechanisms are put forward to explain this result. This molecular structural mechanism provides a new tool for rice breeders to select cultivars with desirable palatability by quantifying the components and molecular structure of leached starch.

Structural characterization of aroid starches by means of chromatographic techniques

Starch functional properties are largely determined by the molecular structure. The weight average molar mass and radius of gyration can be calculated by the analysis of solubilized polymers using AF4-MALLS-DRI systems. The chain length distribution can be determined by analysing debranched starches by gel permeation chromatography (GPC) and high performance anion exchange chromatography (HPAEC-PAD). Aroid starches were used as study case for structure analysis with the abovementioned chromatographic techniques. Amylose and amylopectin chains from aroid starches exhibited weight-average molar mass (Mw) higher than 2.5 × 107 g mol−1 and 5.7 to 13 × 108 g mol−1, respectively. The relatively high values of Mw are correlated to high radius of gyration to both amylose and amylopectin molecules (253–291 nm and 311–410 nm, respectively). The hydrodynamic coefficient (υG) of amylose and amylopectin was 0.6–0.7 and 0.28–0.35, respectively, suggesting random coil conformation for amylose and spherical conformation for amylopectin. The conformation of amylopectin was confirmed by GPC and HPAEC-PAD with the presence of high population of short amylopectin chains (DP 6–12–30% and DP 13–24–50%).

Effects of pectin on molecular structural changes in starch during digestion

Starch digestion rate is strongly related to metabolic diseases such as obesity and diabetes. Starchy foods always contain non-starch components, which can affect starch digestibility. Mixtures of ungelatinized corn starch with a common non-starch component, pectin, were used to investigate pectin’s effect on starch digestibility rate and evolution of starch molecular structure during digestion using amyloglucosidase and pancreatin. The whole-molecule size distribution and the chain-length distribution of chains were measured by size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis. Digestion profiles and changes in molecular size distributions of whole and debranched digesta during digestion show that addition of pectin significantly decreased starch digestion rates. While pectin did not change the amylose/amylopectin ratio during most of the digestion, it decreased the digestion rate of short amylopectin chains compared to long ones. UV–visible spectral data suggested that a major contributor to this digestion rate change is from substantial pectin/amyloglucosidase interaction. This suggests an approach to designing nutritionally more beneficial starch-based foods by taking account of interactions between pectin and digestive enzymes.

Structure, physicochemical characteristics, and functional properties of starches isolated from yellow (Curcuma longa ) and black (Curcuma caesia ) turmeric rhizomes

Starch, a dominant component of the turmeric rhizomes, has been traditionally used as a food coloring and functional foods. The objective of this study is to investigate the structure and physicochemical characteristics and functional properties of the yellow (Curcuma longa) and black (Curcuma caesia) turmeric starches. The C. longa and C. caesia starches contained the triangular to oval shaped granules, which exhibited similar B-type crystalline structure and amylose content. However, the C. longa starch had higher chain length of amylose and more short branching chains of amylopectin resulting in lower gelatinization temperature but higher transition enthalpy as compared to the C. caesia starch. Both C. longa and C. caesia starches showed broad peak viscosities with no breakdown indicating greater stability of these starches under heat and shear conditions, in which the C. longa had significantly higher viscosity than did the C. caesia starch. The resistant starch contents of the C. longa and C. caesia starches were 24 and 20%, respectively. Moreover, the C. longa starch contained higher amounts of total phenolics and curcumin resulting in stronger antioxidant capacity as compared to the C. caesia starch. As a result, the C. longa and C. caesia starches could be used as a functional food in both food and pharmaceutical industries.

Systems Genetics Identifies a Novel Regulatory Domain of Amylose Synthesis.

A deeper understanding of the regulation of starch biosynthesis in rice (Oryza sativa) endosperm is crucial in tailoring digestibility without sacrificing grain quality. In this study, significant association peaks on chromosomes 6 and 7 were identified through a genomewide association study (GWAS) of debranched starch structure from grains of a 320 indica rice diversity panel using genotyping data from the high-density rice array. A systems genetics approach that interrelates starch structure data from GWAS to functional pathways from a gene regulatory network identified known genes with high correlation to the proportion of amylose and amylopectin. An SNP in the promoter region of Granule Bound Starch Synthase I was identified along with seven other SNPs to form haplotypes that discriminate samples into different phenotypic ranges of amylose. A GWAS peak on chromosome 7 between LOC_Os07g11020 and LOC_Os07g11520 indexed by a nonsynonymous SNP mutation on exon 5 of a bHLH transcription factor was found to elevate the proportion of amylose at the expense of reduced short-chain amylopectin. Linking starch structure with starch digestibility by determining the kinetics of cooked grain amylolysis of selected haplotypes revealed strong association of starch structure with estimated digestibility kinetics. Combining all results from grain quality genomics, systems genetics, and digestibility phenotyping, we propose target haplotypes for fine-tuning starch structure in rice through marker-assisted breeding that can be used to alter the digestibility of rice grain, thus offering rice consumers a new diet-based intervention to mitigate the impact of nutrition-related noncommunicable diseases.

Impact of molecular structure on the physicochemical properties of starches isolated from different field pea (Pisum sativum L.) cultivars grown in Saskatchewan, Canada.

The objective of this study was to determine the molecular structure and properties of recently released cultivars of field peas [CDC Golden (CDCG), Abarth (ABAR), CDC Patrick (CDCP) and CDC Amarillo (CDCA)] grown at different locations in Saskatchewan, Canada. Starch yield (on whole seed basis), apparent amylose, total lipid and specific surface area were in the range 34-37%, 38.2-42.6%, 1.07-1.38% and 0.31-0.38m2/g, respectively. The proportion of short (DP 6-12) amylopectin chains, amylopectin branching density, molecular order, crystallinity, crystalline heterogeneity, gelatinization transition temperatures, pasting temperatures, peak viscosity, extent of acid hydrolysis, and resistant starch content were higher in CDCG and ABAR. However, amylopectin long chains (DP 13-26), average chain length and thermal stability were higher in CDCP and CDCA. The results of this study showed that differences in physicochemical properties among cultivars were mainly influenced by amylopectin chain length distribution, amylopectin branching density and co-crystallization of amylose with amylopectin.

Kernel and Starch Properties of U.S. and Imported Medium‐ and Short‐Grain Rice Cultivars

The production of medium‐ and short‐grain rice in the mid‐Southern U.S. rice‐growing region is increasing. This work aimed to identify the quality traits of importance to the markets for these grain types. Twenty‐five medium‐ and short‐grain milled rice samples were collected and analyzed for physical, gelatinization, pasting, and starch structural properties. Six samples were from Arkansas (AR), five from California (CA), and 14 imported (IM). Cluster and principal component analyses showed that the AR samples had greater gelatinization temperature, enthalpy, and percentages of amylopectin long chains (B2 and B3 chains) but lesser kernel whiteness, total setback viscosity, and percentage of amylopectin short chains (A chains) than the CA samples. With the exception of one sample from Taiwan, chemometrics indicated that the IM samples differed from the AR samples (cluster A) in some properties and were grouped into three clusters (clusters B, C, and D). Cluster B samples had properties that were similar to the CA samples; cluster C samples had lower gelatinization temperature and peak viscosity but greater percentages of amylose and A chains than the AR samples; and cluster D samples had lesser paste breakdown but greater final viscosity and percentage of B1 chains than the AR samples. Kernel width, color, and chalk were the primary sources of variation in milled rice appearance. In relation to structure and functionality, the percentages of amylopectin A and B3 chains and amylose content were the major sources of variation.

Effects of organic acid pretreatment on microstructure, functional and thermal properties of unripe banana flour

Starch availability has been implicated in unripe matured banana (Musa species), which when processed yields flour suitable for application in low gluten and composite wheat formulations. Unripe Musa species: Williams, Luvhele, Mabonde and Muomva-red obtained from fruit bunch were pretreated with ascorbic, citric and lactic acids, processed into 50 g of flour and characterised for their functional and thermal properties. Scanning electron microscope of unripe banana flour (UBF) showed varying micrographs of flour, with polygonal for Luvhele, oval for Mabonde, elongated for Muomva-red and between polygonal and spherical for Williams. The bulk density of UBF samples was within the range of 0.66–0.84 g/mL for all organic acid pretreatment while citric acid pretreated UBF had the least browning index. Significant difference (p < 0.05) was recorded in swelling power with no significant difference in water solubility index except for Mabonde UBF. Thermal properties showed single endothermic transition for all UBF samples at various pretreatment concentration. The onset temperature (To) of UBF ranges from 49.82 to 65.59 °C, peak temperature (Tp) from 60.11 to 76.71 °C, conclusion temperature (Tc) from 70.36 to 94.16 °C and enthalpy of gelatinization (ΔH) from 2.61 to 32.24 J/g. Short amylopectin chains present in starch of UBF was attributed to low To, Tp, Tc and ΔH values recorded for Mabonde cultivar, while the contribution of heat-moisture treatment rather than organic acid pretreatment of UBF samples was attributed to different gelatinization and transition temperatures recorded for all cultivars examined.

Thermal and rheological characteristics of mutant rice starches with widespread variation of amylose content and amylopectin structure

Of starch biosynthesis-related enzymes, starch synthases (SSs) and starch branching enzymes (BEs) play important roles in the control of starch structure. Measurements of the particle size distribution, swelling power, differential scanning calorimetry (DSC), X-ray diffraction (XRD) and dynamic viscoelastic measurements were used to investigate the physicochemical properties of rice endosperm starch from SSIIIa, granule-bound starch synthase (GBSSI) and/or BEIIb deficient mutants including double mutants having widespread variation of amylose content and amylopectin structure. The predicted relative starch crystallinity (RSC) of A-type starches and B-type starches of these mutants, as computed based on amylopectin contents, were almost equal. These results suggest that SSIIIa and BEIIb deficiency does not affect the degree of crystallinity of amylopectin. A newly developed double mutant line (ss3a/be2b) with high amylose content (ca. 45%) and a lower proportion of amylopectin short chains showed a higher temperature of gelatinization. Moreover, retrogradation of the gel was extremely rapid. Additionally, be2b with extremely low proportion of amylopectin short chains and lower amylose contents (28%) showed higher gelatinization temperature and more rapid retrogradation than ss3a, with a lower proportion of amylopectin long chains with DP ≤ 33 and higher amylose content (30%). Granules of ss3a/be2b and be2b in gels after viscoelastic measurement were mostly maintained, indicating that most starch granules were not ruptured during heating. These results clarify that not only amylose contents but also the fine structure in amylopectin strongly affected rice gel viscoelastic properties.

Allelic variations in the soluble starch synthase II gene family result in changes of grain quality and starch properties in rice (Oryza sativa L.)

SUMMARYSoluble starch synthase II (SSII) plays an important role in the biosynthesis of starch and in rice it consists of three isoforms encoded by SSII-1, SSII-2 and SSII-3. However, the genetic effects of various SSII alleles on grain quality have not been systematically characterized. In the present study, the japonica alleles on SSII-1, SSII-2 and SSII-3 (SSIIa) loci from a japonica cultivar, Suyunuo, were respectively introgressed by molecular marker-assisted selection into a typical indica cultivar, Guichao2, through successive backcrossing, generating three sets of near-isogenic lines (NILs). Grain quality and starch property analysis showed that NIL-SSII-3j exhibited significant decreases in the following parameters: amylose content, average granule size, and setback viscosity and consistency; but increases in peak viscosity, hot paste viscosity, gelatinization temperature and relative crystallinity. Moreover, the proportion of short amylopectin chains and branching degree also increased when compared with those of NIL-SSII-3i (Guochao2). Similar effects were observed in NIL-SSII-1j, and certain alterations in the fine structure of starch (granule size) were revealed. However, NIL-SSII-2j did not exert significant effect on grain quality and starch properties. In brief, among the SSII gene family, the functional diversity occurred on SSII-1 and SSII-3, and not on SSII-2. Therefore, it appears that more attention should be directed to SSII-1 and SSII-3 loci for improving the eating and cooking quality of rice.