Rice Subgroups Research Articles

Origin of the presence/absence variation of the LTIA1/LTIA2 mini-ribonuclease III genes required for low-temperature growth in rice

A rice low temperature-induced albino variant was determined by the recessive ltia1 and ltia2 genes. LTIA1 and LTIA2 encode highly conserved mini-ribonucleases III located in chloroplasts and expressed in aerial parts of the plant. At low temperature, LTIA1 and LTIA2 redundantly affect chlorophyll levels, non-photochemical quenching, photosynthetic quantum yield of PS II and seedling growth. LTIA1 and LTIA2 proteins are involved in splicing of atpF and the biogenesis of 16S and 23S rRNA in chloroplasts. Presence/absence variation of LTIA1, the ancestral copy, was found only in japonica but that of LTIA2 in all rice subgroups. Accessions with LTIA2 presence tended to be distributed more remote from the equator compared to those with LTIA2 absence. LTIA2 duplicated from LTIA1 at the early stage of divergence of the AA genome Oryza species but deleted againin O. nivara. In cultivated rice, absence of LTIA2 is derived from O. nivara. LTIA1 absence occurred more recently in japonica.

Evolutionary systems biology reveals patterns of rice adaptation to drought-prone agro-ecosystems.

Rice (Oryza sativa) was domesticated around 10,000 years ago and has developed into a staple for half of humanity. The crop evolved and is currently grown in stably wet and intermittently dry agro-ecosystems, but patterns of adaptation to differences in water availability remain poorly understood. While previous field studies have evaluated plant developmental adaptations to water deficit, adaptive variation in functional and hydraulic components, particularly in relation to gene expression, has received less attention. Here, we take an evolutionary systems biology approach to characterize adaptive drought resistance traits across roots and shoots. We find that rice harbors heritable variation in molecular, physiological, and morphological traits that is linked to higher fitness under drought. We identify modules of co-expressed genes that are associated with adaptive drought avoidance and tolerance mechanisms. These expression modules showed evidence of polygenic adaptation in rice subgroups harboring accessions that evolved in drought-prone agro-ecosystems. Fitness-linked expression patterns allowed us to identify the drought-adaptive nature of optimizing photosynthesis and interactions with arbuscular mycorrhizal fungi. Taken together, our study provides an unprecedented, integrative view of rice adaptation to water-limited field conditions.

Genomic signatures of domestication and adaptation during geographical expansions of rice cultivation

Rice (Oryza sativa L.), a global staple food now grown on all inhabited continents, was domesticated from its wild progenitor, O. rufipogon Griff., in tropical and subtropical regions of Asia (Oka, 1988). After domestication, the expansions of rice landraces into the present-day range required a diverse array of adaptations to local environments, which included changes in daylight sensitivity, expanded thermal tolerance (for excess cold and heat), adaptations to water availability (drought and waterlogging), and resistance to biotic stresses (Garris et al., 2005; Glaszmann, 1987).

Fate of trichothecenes B in rice and parboiling process as a mitigation strategy

This study was designed to assess these two critical safety issues in the rice supply chain. First, DON and its acetylated derivatives, 3-ADON and 15-ADON, occurrence was evaluated in different commercial rice subgroups. Subsequently, DON migration dynamics during parboiling was investigated in rice samples from lowland and upland cultivars. These two main goals were designed to increase understanding of contamination risk in rice by trichothecenes and, subsequently, to enable the proposal of a mitigation strategy. The VA-MSPD trichothecenes determination method proved to be reliable and efficient to evaluate rice contamination, with recoveries between 73.4 and 117.4%. Approximately 43.3% of the commercial samples, obtained randomly from the local market, tested positive for DON and/or 15-ADON with contamination level below the LOQ (0.50 μg.kg−1). Whole rice and whole parboiled rice subgroups showed highest incidence, 66.7% and 83.3%, respectively. During parboiling migration studies, milder conditions in gelatinization step had decreased DON migration into the starchy endosperm. With this condition, the mycotoxin remained in the bran in both cultivars (12.0 and 13.4%). Therefore, demonstrating that it is possible to mitigate mycotoxins in polished rice products with minor alterations to current supply chain processes and enhancing security of this staple food.

Genome-Wide Association Analysis Dissects the Genetic Basis of the Grain Carbon and Nitrogen Contents in Milled Rice

BackgroundCarbon (C) and nitrogen (N) are two fundamental components of starch and protein, which are important determinants of grain yield and quality. The food preferences of consumers and the expected end-use of grains in different rice-growing regions require diverse varieties that differ in terms of the grain N content (GNC) and grain C content (GCC) of milled rice. Thus, it is important that quantitative trait loci (QTLs)/genes with large effects on the variation of GNC and GCC are identified in breeding programs.ResultsTo dissect the genetic basis of the variation of GNC and GCC in rice, the Dumas combustion method was used to analyze 751 diverse accessions regarding the GNC, GCC, and C/N ratio of the milled grains. The GCC and GNC differed significantly among the rice subgroups, especially between Xian/Indica (XI) and Geng/Japonica (GJ). Interestingly, in the GJ subgroup, the GNC was significantly lower in modern varieties (MV) than in landraces (LAN). In the XI subgroup, the GCC was significantly higher in MV than in LAN. One, six, and nine QTLs, with 55 suggestively associated single nucleotide polymorphisms, were detected for the GNC, GCC, and C/N ratio in three panels during a single-locus genome-wide association study (GWAS). Three of these QTLs were also identified in a multi-locus GWAS. We screened 113 candidate genes in the 16 QTLs in gene-based haplotype analyses. Among these candidate genes, LOC_Os01g06240 at qNC-1.1, LOC_Os05g33300 at qCC-5.1, LOC_Os01g04360 at qCN-1.1, and LOC_Os05g43880 at qCN-5.2 may partially explain the significant differences between the LAN and MV. These candidate genes should be cloned and may be useful for molecular breeding to rapidly improve the GNC, GCC, and C/N ratio of rice.ConclusionsOur findings represent valuable information regarding the genetic basis of the GNC and GCC and may be relevant for enhancing the application of favorable haplotypes of candidate genes for the molecular breeding of new rice varieties with specific grain N and C contents.

Spatial Effects and GWA Mapping of Root Colonization Assessed in the Interaction Between the Rice Diversity Panel 1 and an Arbuscular Mycorrhizal Fungus.

If water saving methods of rice management are to be adopted, the interaction between rice plants and arbuscular mycorrhizal (AM) fungi will grow in agronomic significance. As yet there are very few studies on the interaction between rice and AM fungi and none on host genetics. A subset 334 cultivars from the Rice Diversity Panel 1 were grown in 250 L boxes filled with phosphorus (P) deficient aerobic soil without addition, with added rock phosphate and with rock phosphate and the AM fungus Rhizophagus irregularis. Statistical analysis of position of plants revealed a positive effect of their neighbors on their dry weight which was stronger in the presence of rock phosphate and even stronger with rock phosphate and AM fungi. A weak but significant difference in the response of cultivars to AM fungus treatment in terms of shoot dry weight (SDW) was revealed. Neighbor hyphal colonization was positively related to a plant’s hyphal colonization, providing insights into the way a network of AM fungi interact with multiple hosts. Hyphal colonization ranged from 21 to 89%, and 42% of the variation was explained by rice genotype. Colonization was slightly lower in aus cultivars than other rice subgroups and high in cultivars from the Philippines. Genome wide association (GWA) mapping for hyphal colonization revealed 23 putative quantitative trait loci (QTLs) indicating there is an opportunity to investigate the impact of allelic variation in rice on AM fungal colonization. Using published transcriptomics data for AM response in rice, some promising candidate genes are revealed under these QTLs being a calcium/calmodulin serine/threonine protein kinase at 4.9 Mbp on chromosome 1, two ammonium transporters genes at 24.6 Mbp on chromosome 2 and a cluster of subtilisin genes at 1.2 Mbp on chromosome 4. Future studies should concentrate on the biological significance of genetic variation in rice for AM colonization.

Development of a core SNP arrays based on the KASP method for molecular breeding of rice

BackgroundThe development and utilization of genetic markers play a pivotal role in marker-assisted breeding of rice cultivars during pyramiding of valuable genes. Among molecular markers, SNPs have become the most promising due to their wide distribution within genomes and suitability for high -throughput automated genotyping. Although metadata of SNPs have been identified via next generation sequencing in rice, a large gap between the development of SNP markers and the application in breeding still exists. To promote the application of SNP markers based on the KASP (Kompetitive Allele-Specific PCR) method in rice breeding, a set of core SNP arrays was built via the screening of SNP databases and literature resources based on the KASP method.ResultsFive hundred and ninety six SNPs classified into eight subsets including quality control, indica-indica variation, highly polymorphic, functional genes, key genes targeting sites, gene cloned region, important trait associated and gap filling sites were chosen to design KASP primers and 565 out of them were successfully designed, and the assay design success rate was 94.8%. Finally, 467 out of the 565 successfully-designed SNPs can display diversity at the loci were used to develop a set of core SNP arrays. To evaluate the application value of the core SNP markers in rice breeding, 481 rice germplasms were genotyped with three functional KASP markers designed from the sequences of GBSSI, SSIIa, and Badh2 from the core SNP arrays for estimation of their grain quality performance. Eighteen rice lines, including Xiangwanxian 13, Basmati 370, Ruanhua A, and PR 33319–9–1-1-5-3-5-4-1, harbor all three favorable alleles. The core KASP arrays were also used for rice germplasm assessment, genetic diversity and population evaluation. Four hundred and eighty-one rice germplasms were divided into 3 groups: POP1, POP2 and POP3. POP1 and POP2 were indica rice subgroups consisting of 263 and 186 rice germplasms, respectively. POP3 was a japonica rice subgroup consisting of 32 rice germplasms. The average FST value for the three subgroups was 0.3501; the FST value of POP1 and POP3 was the largest (0.5482), while that of POP1 and POP2 was the smallest (0.0721). The results showed that the genetic distance between the japonica and indica rice subspecies was large, indicating that the core SNP markers were effective at discriminating the population structure of the germplasms. Finally, the core KASP arrays were used for association analysis with milled grain traits. A total of 31 KASP markers were significantly associated (P < 0.01) with ML and the LWR. Among the 31 markers, 13 were developed based on cloned genes or on identified loci related to yield traits. Notably, several KASP markers associated with grain quality were also found to be associated with brown planthopper resistance or green leafhopper resistance simultaneously.ConclusionsThe core KASP arrays developed in our study were efficient and versatile for rice germplasm assessment, genetic diversity and population evaluation and are valuable for promoting SNP molecular breeding in rice. Our study demonstrated that useful assays combined with molecular breeding can be exploited for important economic trait improvement in rice breeding.

Exploring factors affecting anther culture in rice (Oryza sativa L.)

Anther culture is an important in vitro culture technique for production of double haploids. It is largely species and genotype-specific. Asian cultivated rice (O. sativa, ssp. indica) is recalcitrant to anther culture which limits its practical application in rice breeding. Several researchers tried to optimize the media recipes and culture techniques for callus induction and plantlet regeneration. Negligible response to callus induction and recovery of higher frequency of albino plants are the major hindrance for use of the technique in crop improvement. Shortening the culture period and sexual hybridization of rice sub-groups (japonica/indica) may be adopted to improve green plant regeneration from anther-derived callus in indica rice. However, genetic transformation technology using individual genes related to different aspects of anther culture could be a more direct approach. Besides, the role of genotypes, physiological status of donor plant, developmental stage of pollen, pre-treatment, culture media, phytohormones and culture conditions for successful anther culture have been discussed. Key words: Anther culture, factors for anther culture, double haploids, genetic improvement, rice.

Anther culture in rice: Progress and breeding perspective

Anther culture is an important biotechnological tool for the rapid recovery of fixed breeding lines in rice. The method is largely species- and genotype-specific. Indica rice is known to have a recalcitrant genetic background. Oryza glaberrima responds better to the anther culture than O. sativa while japonica sub-group is more responsive to microspore embryogenesis than Indica types. Media recipes and culture techniques have been standardized for callus induction and green plantlet regeneration using Indica and Japonica varieties as well as their inter se hybrids. Additive effects seem more important than dominant effects of the genes concerned for callus induction while preponderance of dominant effects is reported for regeneration response. Sexual hybridization of rice sub-groups (Japonica x Indica) followed by the selection of favourable QTL for green plant regeneration may be adopted to improve plant regeneration from anther-derived callus in Indica rice. However, genetic transformation technology using individual genes related to different aspects of anther culture could be a more direct approach. This paper reviews the progress and breeding perspective of anther culture in rice for genetic improvement of agronomic- and stress-related traits using double haploid breeding.

Genomic adaptation of flowering‐time genes during the expansion of rice cultivation area

The diversification of flowering time in response to natural environments is critical for the spread of crops to diverse geographic regions. In contrast with recent advances in understanding the molecular basis of photoperiodic flowering in rice (Oryza sativa), little is known about how flowering-time diversification is structured within rice subspecies. By analyzing genome sequencing data and a set of 429 chromosome segment substitution lines (CSSLs) originating from 10 diverse rice accessions with wide distributions, we revealed diverse effects of allelic variations for common flowering-time quantitative trait loci in the recipient's background. Although functional variations associated with a few loci corresponded to standing variations among subspecies, the identified functional nucleotide polymorphisms occurred recently after rice subgroup differentiation, indicating that the functional diversity of flowering-time gene sequences was not particularly associated with phylogenetic relationship between rice subspecies. Intensive analysis of the Hd1 genomic region identified the signature of an early introgression of the Hd1 with key mutation(s) in aus and temperate japonica accessions. Our data suggested that, after such key introgressions, new mutations were selected and accelerated the flowering-time diversity within subspecies during the expansion of rice cultivation area. This finding may imply that new genome-wide changes for flowering-time adaptation are one of the critical determinants for establishing genomic architecture of local rice subgroups. In-depth analyses of various rice genomes coupling with the genetically confirmed phenotypic changes in a large set of CSSLs enabled us to demonstrate how rice genome dynamics has coordinated with the adaptation of cultivated rice during the expansion of cultivation area.

Multivariable Analysis of Nutritional and Socio-Economic Profiles Shows Differences in Incident Anemia for Northern and Southern Jiangsu in China.

Anemia is a prevalent public health problem associated with nutritional and socio-economic factors that contribute to iron deficiency. To understand the complex interplay of risk factors, we investigated a prospective population sample from the Jiangsu province in China. At baseline, three-day food intake was measured for 2849 individuals (20 to 87 years of age, mean age 47 ± 14, range 20–87 years, 64% women). At a five-year follow-up, anemia status was re-assessed for 1262 individuals. The dataset was split and age-matched to accommodate cross-sectional (n = 2526), prospective (n = 837), and subgroup designs (n = 1844). We applied a machine learning framework (self-organizing map) to define four subgroups. The first two subgroups were primarily from the less affluent North: the High Fibre subgroup had a higher iron intake (35 vs. 21 mg/day) and lower anemia incidence (10% vs. 25%) compared to the Low Vegetable subgroup. However, the predominantly Southern subgroups were surprising: the Low Fibre subgroup showed a lower anemia incidence (10% vs. 27%), yet also a lower iron intake (20 vs. 28 mg/day) compared to the High Rice subgroup. These results suggest that interventions and iron intake guidelines should be tailored to regional, nutritional, and socio-economic subgroups.

Escape to Ferality: The Endoferal Origin of Weedy Rice from Crop Rice through De-Domestication.

Domestication is the hallmark of evolution and civilization and harnesses biodiversity through selection for specific traits. In regions where domesticated lines are grown near wild relatives, congeneric sources of aggressive weedy genotypes cause major economic losses. Thus, the origins of weedy genotypes where no congeneric species occur raise questions regarding management effectiveness and evolutionary mechanisms responsible for weedy population success. Since eradication in the 1970s, California growers avoided weedy rice through continuous flood culture and zero-tolerance guidelines, preventing the import, presence, and movement of weedy seeds. In 2003, after decades of no reported presence in California, a weedy rice population was confirmed in dry-seeded fields. Our objectives were to identify the origins and establishment of this population and pinpoint possible phenotypes involved. We show that California weedy rice is derived from a different genetic source among a broad range of AA genome Oryzas and is most recently diverged from O. sativa temperate japonica cultivated in California. In contrast, other weedy rice ecotypes in North America (Southern US) originate from weedy genotypes from China near wild Oryza, and are derived through existing crop-wild relative crosses. Analyses of morphological data show that California weedy rice subgroups have phenotypes like medium-grain or gourmet cultivars, but have colored pericarp, seed shattering, and awns like wild relatives, suggesting that reversion to non-domestic or wild-like traits can occur following domestication, despite apparent fixation of domestication alleles. Additionally, these results indicate that preventive methods focused on incoming weed sources through contamination may miss burgeoning weedy genotypes that rapidly adapt, establish, and proliferate. Investigating the common and unique evolutionary mechanisms underlying global weed origins and subsequent interactions with crop relatives sheds light on how weeds evolve and addresses broader questions regarding the stability of selection during domestication and crop improvement.

Genome-wide resequencing of KRICE_CORE reveals their potential for future breeding, as well as functional and evolutionary studies in the post-genomic era

BackgroundRice germplasm collections continue to grow in number and size around the world. Since maintaining and screening such massive resources remains challenging, it is important to establish practical methods to manage them. A core collection, by definition, refers to a subset of the entire population that preserves the majority of genetic diversity, enhancing the efficiency of germplasm utilization.ResultsHere, we report whole-genome resequencing of the 137 rice mini core collection or Korean rice core set (KRICE_CORE) that represents 25,604 rice germplasms deposited in the Korean genebank of the Rural Development Administration (RDA). We implemented the Illumina HiSeq 2000 and 2500 platform to produce short reads and then assembled those with 9.8 depths using Nipponbare as a reference. Comparisons of the sequences with the reference genome yielded more than 15 million (M) single nucleotide polymorphisms (SNPs) and 1.3 M INDELs. Phylogenetic and population analyses using 2,046,529 high-quality SNPs successfully assigned rice accessions to the relevant rice subgroups, suggesting that these SNPs capture evolutionary signatures that have accumulated in rice subpopulations. Furthermore, genome-wide association studies (GWAS) for four exemplary agronomic traits in the KRIC_CORE manifest the utility of KRICE_CORE; that is, identifying previously defined genes or novel genetic factors that potentially regulate important phenotypes.ConclusionThis study provides strong evidence that the size of KRICE_CORE is small but contains high genetic and functional diversity across the genome. Thus, our resequencing results will be useful for future breeding, as well as functional and evolutionary studies, in the post-genomic era.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2734-y) contains supplementary material, which is available to authorized users.

The Power of Inbreeding: NGS-Based GWAS of Rice Reveals Convergent Evolution during Rice Domestication

Low-coverage whole-genome sequencing is an effective strategy for genome-wide association studies in humans, due to the availability of large reference panels for genotype imputation. However, it is unclear whether this strategy can be utilized in other species without reference panels. Using simulations, we show that this approach is even more relevant in inbred species such as rice (Oryza sativa L.), which are effectively haploid, allowing easy haplotype construction and imputation-based genotype calling, even without the availability of large reference panels. We sequenced 203 rice varieties with well-characterized phenotypes from the United States Department of Agriculture Rice Mini-Core Collection at an average depth of 1.5× and used the data for mapping three traits. For the first two traits, amylose content and seed length, our approach leads to direct identification of the previously identified causal SNPs in the major-effect loci. For the third trait, pericarp color, an important trait underwent selection during domestication, we identified a new major-effect locus. Although known loci can explain color variation in the varieties of two main subspecies of Asian domesticated rice, japonica and indica, the new locus identified is unique to another domesticated rice subgroup, aus, and together with existing loci, can fully explain the major variation in pericarp color in aus. Our discovery of a unique genetic basis of white pericarp in aus provides an example of convergent evolution during rice domestication and suggests that aus may have a domestication history independent of japonica and indica.

Natural variation of rice blast resistance gene Pi-d2.

Studying natural variation in rice resistance genes of cultivated and wild rice relatives can predict resistance stability to rice blast fungus. In the present study, the protein coding regions of the rice R gene Pi-d2 in 35 rice accessions, including Oryza sativa L. subsp. indica Kato (Aus), indica (IND), temperate japonica (TEJ), tropical japonica (TRJ), aromatic (ARO); subgroups of Oryza sativa; 6 accessions of wild rice varieties; O. nivara; and O. rufipogon were analyzed. A total of 13 nucleotide differences were found in the open reading frames (ORFs) of Pi-d2. Translation of these ORFs revealed 9 variants; 3 were novel Pi-d2 variants. Variants H2 and H5 were identified in accessions of cultivated rice and O. nivara, H1, H3, H4, H6, and H8 were only identified in cultivated rice. H2 and H5 were the common types of IND and O. nivara, H8 was the common type of TRJ and AUS, H6 was the specific type of AUS, and H3 was the specific type of ARO. H7 and H9 were specific haplotypes of O. nivara and O. rufipogon, respectively. These findings demonstrate that Pi-d2 variants are useful indicators for each subgroup, and Pi-d2 is an ancient gene that predates speciation of rice subgroups.

Metabolic variation between japonica and indica rice cultivars as revealed by non-targeted metabolomics.

Seed metabolites are critically important both for plant development and human nutrition; however, the natural variation in their levels remains poorly characterized. Here we profiled 121 metabolites in mature seeds of a wide panel Oryza sativa japonica and indica cultivars, revealing correlations between the metabolic phenotype and geographic origin of the rice seeds. Moreover, japonica and indica subspecies differed significantly not only in the relative abundances of metabolites but also in their corresponding metabolic association networks. These findings provide important insights into metabolic adaptation in rice subgroups, bridging the gap between genome and phenome, and facilitating the identification of genetic control of metabolic properties that can serve as a basis for the future improvement of rice quality via metabolic engineering.

Characterization of OsLCT1, a cadmium transporter from indica rice (Oryza sativa)

Molecular understanding of cadmium (Cd) transport in indica rice (Oryza sativa) is still insufficient, although indica rice generally has a potential to accumulate higher Cd in shoots and grains than japonica rice. We have previously demonstrated that OsLCT1 is a Cd transporter gene responsible for grain Cd accumulation in the japonica model cultivar Nipponbare. In this study, we isolated OsLCT1 cDNA from Kasalath, a model indica (aus subgroup) cultivar and conducted cation transport activity assays in yeast and mRNA expression analysis in plants. The deduced amino acid sequence of Kasalath OsLCT1 is 91.2% identical and 93.8% similar to that of Nipponbare OsLCT1. We established the yeast heterologous system expressing the Kasalath allele of OsLCT1. Elemental profiling of the yeast cells suggested an efflux activity of Kasalath OsLCT1 for Cd, K, Mg, Ca and Mn, but not for Fe, Zn, Cu and Na. This substrate specificity was identical to that of the Nipponbare version. Quantitative real time-polymerase chain reaction (RT-PCR) showed that expression of OsLCT1 in Kasalath was higher in reproductive stage than in vegetative stage. The expression level of OsLCT1 was significantly higher in Kasalath than in Nipponbare. Phylogenetic analysis found several LCT1-like genes only in grass plants. OsLCT1 is the sole copy in the rice genome and is conserved among each rice subgroup. These newly found low-affinity cation transporter (LCT) homologs will provide a basis for further understanding of LCT-mediated Cd transport.

Ontogenetic changes in vitamin C in selected rice varieties

Vitamin C (L-ascorbic acid) is a key antioxidant for both plants and animals. In plants, ascorbate is involved in several key physiological processes including photosynthesis, cell expansion and division, growth, flowering, and senescence. In addition, ascorbate is an enzyme cofactor and a regulator of gene expression. During exposure to abiotic stresses, ascorbate counteracts excessive reactive oxygen species within the cell and protects key molecules, including lipids, proteins, and nucleic acids, from irreversible damage. In this study we focus on understanding how ascorbate levels are controlled in rice (Oryza sativa) during plant development and in response to light intensity and photoperiod. Our results indicate that in rice ascorbate metabolism follows a different pattern compared to other species. In the rice accessions we analyzed, total foliar ascorbate content increases during development and peaks at the vegetative 2-4 and the reproductive 4 stages, whereas other research has shown that in Arabidopsis thaliana and other dicots, ascorbate content declines with plant age. The pattern in rice does not seem to change when plants were grown under increasing light intensity: 150, 400 or 1200-1500 μmol m(-2) s(-1). We observed little diurnal variation in AsA content in rice and did not see a steady decline during the dark period as has been reported in other species such as Arabidopsis and tomato. The total foliar ascorbate content of twenty-three rice accessions from four major rice subgroups was compared. These genotypes differed as much as eight-fold in ascorbate content at the V2 stage indicating the potential to enhance vitamin C levels in genotypes of global interest via breeding approaches.

Variations in Bran Carotenoid Levels within and between Rice Subgroups

Rice (Oryza sativa L.) is a major grain in the human diet and carotenoids are valuable antioxidants. However, little is known about varietal differences in the carotenoid contents of the rice bran. The objective of this study is to determine the relative differences in bran carotenoid levels among all the five subgroups of rice. Measurements were made by a recently described, rapid non-destructive fluorescence quenching method. Confirmation by high performance liquid chromatography (HPLC) after solvent extraction of the bran indicated that the major carotenoid was lutein. Our data showed that carotenoid levels were stable over 10 years of storage. Tropical japonica rice, the most consumed subgroup in the United States, tended to have the lowest levels of carotenoids in the bran while temperate japonicas had the highest. These differences in carotenoid content may open up new opportunities for identifying or breeding rice varieties with higher nutritional value.

Identificação de Aspergillus spp: toxigênico em arroz

The chemical composition and its methods of cultivation, make rice plants susceptible to fungi and consequently to mycotoxins contamination. Considering the expressive rice consumption and given the possibility that it maybe a potential source of mycotoxins, special attention should be devoted to its quality. Thus, this study was carried out to evaluate the Aspergillus species as to its toxigenic capacities in different rice subgroups. Thirty one and rice brands among the most popular brands sold in the city of Lavras - MG, were collected as samples, (21) polished white and (10) parboiled, respectively. Unlike other subgroups, the incidence of Aspergillus flavus and Aspergillus niger in the samples of polished white rice increased significantly after disinfecting. It was observed that 50% of the Aspergillus flavus and 50% of the Aspergillus niger were considered toxigenic in the white and polished rice subgroup. In the sample of parboiled rice, 67% of the Aspergillus flavus were potential producers. The Aspergillus ochraceus was not toxigenic. This study showed that the toxigenic fungi are present in rice, and this fact is relevant due to the importance of this cereal worldwide.