Feifei Xu

Phenolic acids, anthocyanins, and antioxidant capacity in rice (Oryza sativa L.) grains at four stages of development after flowering.

This study investigated differences in total phenolic content (TPC), antioxidant capacity, and phenolic acids in free, conjugated and bound fractions of white (unpolished), red and black rice at 1-, 2-, and 3-weeks of grain development after flowering and at maturity. Unlike the TPC (mg/100g) of white rice (14.6-33.4) and red rice (66.8-422.2) which was significantly higher at 1-week than at later stages, the TPC of black rice (56.5-82.0) was highest at maturity. The antioxidant capacity measured by DPPH radical scavenging and ORAC methods generally followed a similar trend as TPC. Only black rice had detectable anthocyanins (26.5-174.7mg/100g). Cyanidin-3-glucoside (C3G) and peonidin-3-glucoside (P3G) were the main anthocyanins in black rice showing significantly higher levels at 2- and 3-weeks than at 1-week development and at maturity. At all stages, the phenolic acids existed mainly in the bound form as detected by HPLC and confirmed by LC-MS/MS. Black rice (20.1-31.7mg/100g) had higher total bound phenolic acids than white rice and red rice (7.0-11.8mg/100g). Protocatechuic acid was detected in red rice and black rice with relatively high levels at 1-week development (1.41mg/100g) and at maturity (4.48mg/100g), respectively. Vanillic acid (2.4-5.4mg/100g) was detected only in black rice where it peaked at maturity. p-Coumaric acid (<3.5mg/100g) did not differ significantly at most stages with somewhat high levels at 1-week for red and black rice. Ferulic acid (4.0-17.9mg/100g), the most abundant bound phenolic acid, had an inconsistent trend with higher levels being observed in black rice where it peaked at maturity. Isoferulic acid levels (0.8-1.6mg/100g) were generally low with slightly elevated values being observed at maturity. Overall black rice had higher total bound phenolic acids than white and red rice while white rice at all stages of development after flowering.

Rapid Identification of Major QTLs Associated with Rice Grain Weight and Their Utilization

To uncover the genetics of rice grain weight, we constructed an RIL population derived from a cross between a large grain accession M201 and a small size variety JY293. Specific Locus Amplified Fragment Sequencing (SLAF-Seq) technology was used to genotype two bulked DNA pools made from individual DNA of the heaviest 30 lines and the lightest 30 lines according to the 1000 grain weight (TGW). Bulked segregant analysis (BSA) was used to identify SLAFs strongly associated with TGW. Two marker-intensive regions at 24,600,000–24,850,000 bp and 25,000,000–25,350,000 bp on chromosome 3 were identified tightly related to the TGW. Then a linkage map of chromosome 3 was constructed with SSR markers and some SLAF derived single nucleotide polymorphisms (SNPs). Quantitative trait locus (QTL) mapping for TGW, grain length, grain width, and grain thickness revealed one major QTL in the second hot-region and two other minor QTLs for grain weight. These three QTLs displayed hierarchical effects on grain length and grain weight in order of qTGW3.2 (qGL3) qTGW3.1 (GS3) qTGW3.3. Multiple comparisons of means among the eight combinations of 3 QTLs revealed that the lines with two of three QTLs deriving from M201 displayed a large grain weight phenotype (TGW 40.2g, average data of three years) and lines with both qTGW3.1 and qTGW3.3 alleles from M201 (42.5g) had similar grain weight to the qTGW3.2 (40.8g) alone. Two strategies with similar effectiveness were proposed to improve grain weight by marker-assisted selection (MAS). One is to introduce the novel qTGW3.2 allele alone, and the other is to pyramid qTGW3.1 and qTGW3.3 alleles together. One new allele of GS3 (39 bp deletion in intron 1) and two SNPs in coding sequence of qGL3 identified in this study from M201 are useful in pyramiding elite alleles for molecular breeding for improvement of rice yield.

Genetic diversity of amylose content and RVA pasting parameters in 20 rice accessions grown in Hainan, China.

Starch physicochemical properties determine the eating and cooking quality of rice. The genetic diversity in the apparent amylose content (AAC) and pasting viscosity parameters of 20 geographically diverse rice accessions were investigated. It was found that AAC and pasting viscosities differed widely among different accessions, but each accession performed relatively stably across two environments. Analysis of variance (ANOVA) indicated that all traits were predominantly controlled by genotypic variance, but the genotype×environment interaction effects were also significant except for AAC and PT. Significant correlations were found for each parameter between 2years (P<0.001). Association mapping identified a total of 22 main-effect quantitative trait loci (QTLs) responsible for all traits except for CPV. This study showed that starch physicochemical properties of rice were highly stable and mainly controlled by genetic factors, and gave insight into the molecular improvement of eating quality using marker assisted breeding with the identified QTLs/genes.

Genotypic variation in phenolic acids, vitamin E and fatty acids in whole grain rice

The genetic diversity of phenolic content (PC), individual phenolic acids, vitamin E isomers (VE) and fatty acids (FA) in the whole grain rice were investigated. The most abundant phenolic acid was ferulic acid ranging from 155.6 to 271.1 μg/g and comprising approximately 40-57% of total phenolic acid (TPA). The predominant tocopherols (T) and tocotrienols (T3) were α-T (6.43-12.67 μg/g) and γ-T3 (12.88-32.75 μg/g). The unsaturated fractions of FAs accounted for 74-81% of the total FAs in rice. Most of the phytochemicals among phenolics and VEs showed significant differences between white and red rice, with red rice demonstrating significantly higher levels. However, white rice had higher content of oleic, linolenic, eicosenoic and total fatty acids than red rice. The wide genetic diversity in whole grain rice allows food processors to have a good selection for producing rice products, and breeders to have new rice lines that can be bred for high nutrient levels.

Analysis of Genotype, Environment, and Their Interaction Effects on the Phytochemicals and Antioxidant Capacities of Red Rice (Oryza sativa L.)

Fourteen red rice varieties were planted in two locations during summer (Hangzhou) and winter (Hainan) to study the effect of genotype and environment on the phytochemicals and antioxidant capacities of rice grain. B-type proanthocyanidins in red rice were detected by LC-MS/MS and quantified by using the vanillin assay. Analysis of variance showed that total phenolic content (TPC), total flavonoid content (TFC) and 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging capacity were mainly affected by environmental factors, which accounted for more than 60% of the total variance. However, total proanthocyanidin content (TPAC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity were equally affected by both genotype and environment. The genotype × environment effects were significant for all traits. The pairwise correlations among TPC, TFC, TPAC, ABTS, and DPPH were also significant (r > 0.900, P < 0.001). Principal component analysis identified the genotypes tha...

Variation in mineral elements in grains of 20 brown rice accessions in two environments

Twenty rice accessions were planted in Hainan province, China, for 2 years to investigate the effects of genotype, environment, and their interactions on the Ca, Mg, Na, K, Fe, Zn, and Cu contents in brown rice. Analysis of variance showed that the Ca, Na and K were mainly affected by the genotypic variance, whereas the Fe, Zn and Cu were mainly affected by the environment variance. The genotype × environment interaction effects for Mg, Na, Zn, and Cu were highly significant (P < 0.001), though it only accounted for a small proportion of the total variation (0.5-16.3%). The correlation analyses showed that Mg was significantly positively correlated with K, Fe, and Zn. A total of 9 and 8 single nucleotide polymorphism (SNP) loci were identified in 2011 and 2012, respectively, which were strongly associated with for Ca, Cu, K, Na, and Zn.

QTL mapping for rice grain quality: a strategy to detect more QTLs within sub-populations

Wx is considered to be the most important gene controlling eating and cooking qualities and pasting properties in rice (Oryza sativa L.). In this study, a recombinant inbred line population derived from indica rice parents differing in apparent amylose content (AAC) was used to detect quantitative trait loci (QTLs) for ten grain quality parameters for rice quality improvement. QTL mapping was performed on the whole population and on two sub-populations based on Wx genotypes. A total of 29 QTLs were found in the whole population. Ten QTLs for 7 traits were detected in the two sub-populations, four of which (qPRO3.1, qPV9, qHPV9, and qCS7) were also detected in the whole population, whereas the other six were QTLs with minor effects that might be covered by the Wx locus. Besides the Wx locus with the largest effect on AAC and most pasting properties, there were another six QTL clusters contributing to grain quality located on chromosomes 2, 3, 5, 6 and 9. It was also found that some QTLs for peak viscosity, breakdown and consistency were closely linked to rice grain shape related QTLs on chromosome 3. A QTL cluster on chromosome 9 for peak viscosity, hot paste viscosity and cold paste viscosity was detectable in the whole population, which was close to the isoamylase 3 (ISA3) locus. A QTL cluster for both peak time and pasting temperature on chromosome 6 was near to the starch synthase I locus, and was potentially a new QTL with minor effect for peak time and pasting temperature. These findings will promote better understanding of the genetic regulation of rice eating and cooking qualities.

Variation in Polyphenols, Tocols, γ-Aminobutyric Acid, and Antioxidant Properties in Whole Grain Rice (Oryza sativa L.) as Affected by Different Germination Time

Dynamic alterations in the polyphenols, tocols, antioxidant activities (AOA), and γ-aminobutyric acid (GABA) contents of white, red, and black germinated rice upon different germination periods were studied. The results indicated that the contents of the free, bound, and total phenolics and AOA steadily increased during germination, even though the free part of colored germinated brown rice (GBR) showed a notable decline at the earlier stages, but still higher than the white rice. The compositions of the nine phenolic acids and six tocols generally accumulated in a time- and variety-dependent manner during the germination process. However, the contents of p-coumaric, ferulic, and sinapic acids displayed a pronounced increase with the duration of germination in all cultivars. The GABA in white, red, and black GBR accumulated to the highest content at the end of germination, which was 4.7, 14.2, and 6.7-fold of their respective nongerminated counterparts. Interestingly, the total anthocyanin content in blac...