Although the overall structure of the chloroplast genome is generally conserved, a number of sequence variations have been identified, which are valuable for plant population and evolutionary studies. Here, we constructed a chloroplast variation map of 30 landrace rice strains of Korean origin, using the Oryza rufipogon chloroplast genome (Genbank: NC_017835) as a reference. Differential distribution of single nucleotide polymorphisms (SNPs) and indels across the rice chloroplast genome is suggestive of a region-specific variation. Population structure clustering revealed the existence of two clear subgroups (indica and japonica) and an admixture group (aus). Phylogenetic analysis of the 30 landrace rice strains and six rice chloroplast references suggested and supported independent evolution of O. sativa indica and japonica. Interestingly, two “aus” type accessions, which were thought to be indica type, shared a closer relationship with the japonica type. One hypothesis is that “Korean aus” was intentionally introduced and may have obtained japonica chloroplasts during cultivation. We also calculated the nucleotide diversity of 30 accessions and compared to six rice chloroplast references, which shown a higher diversity in the indica and aus groups than in the japonica group in lower level substitution diversity.

Rice is the major food for half of the world population. The nutrition component in rice is critical for improvement of people’s health. Vitamin E serves as important antioxidant by quenching the free radical intermediates and thus protects the cell membrane. Because of the high nutritional value and the benefits of vitamin E in human health, increasing the tocochromanol content of major agricultural crops has long been in the focus of breeding programs and genetic engineering approaches. The key genes involved in tocopherol biosynthesis have been elucidated in Arabidopsis and other model organisms. Quantitative trait locus (QTL) study performed in Arabidopsis suggested that some of these key genes and a few additional loci contribute to natural tocopherol variations. Identifying such genetic variations in rice, enrich our understanding of the genetic mechanisms controlling tocopherol variation, which can be directly applied to rice breeding programs. In this study, we used genome-wide association mapping with high-resolution density SNPs of rice core set to identify natural allelic variations, which contribute to tocopherol increase in rice

As one of the most important crop, rice is not only a staple food of half world’s population but a wonderful model plant, which has been leading the evolution and functional genomics study. The next-generation sequencing technology are expediting rice genomic study, by providing a simple but powerful way. In this study, we re-sequenced a core collection of 137 rice accessions from all over the world along with 158 Korean breeding varieties. Finally, 6.3G uniquely mapped reads were obtained, and about 10 million SNPs and ~1.2 million InDels were identified with average sequencing depth of 7.5X. These will help us to maximize our germplasm utilization and assists all the deep research in population dynamics and functional studies. Here, we’d like to show the approaches applied to resequencing data mining and on-going activities.

AGenome-wide association studies (GWAS) have proven a useful technique for identifying genetic loci responsible for natural variation in rice. With the fast developed next-generation sequencing technology, it is possible for people to carry out GWAS by phenotyping different traits. However, how to make full use of huge data, abandon unnecessary data, and solve the problem of data application effectively seems still an obstacle for many researchers. Taking the case of whole-genome resequencing of Korean authentic rice core set, here we present a general technological path of GWAS including: 1) a schematic view of sequencing-based GWAS in rice; 2) a user-friendly and interactive web application for GWAS in rice by the aid of experience from Arabidopsis; 3) Haplotype and association analysis of candidate genes in a certain mechanism pathway, giving 10 starch synthesis genes as example; and 4) functional validation by Trans- and Mata-Omics analysis.

Vitamin E and phytosterols are both valuable nutrients that act as antioxidants in human bodies. Understanding the genetic basis of these traits is necessary for the improvement of nutritional quality by breeding. In this study, 119 rice accessions of diverse origin were genotyped using 232 SSR markers to identify marker–trait associations with Vitamin E and phytosterols in rice. Analysis of population structure revealed four subgroups in the population. Linkage disequilibrium (LD) patterns and distributions are of fundamental importance for genome-wide mapping associations. The mean r2 value for all intra-chromosomal loci pairs was 0.3361. LD between linked markers decreased with distance. Marker–trait associations were investigated using the unified mixed-model approach, considering both population structure (Q) and kinship (K). In total, 81 marker–trait associations were identified using 232 different SSR markers covering 12 chromosomes. The results suggest that association mapping in rice is a viable alternative to quantitative trait loci mapping. The results from this association mapping study will be the basis for improving rice nutritional quality.

Rice(Oryza sativa L.) feeds more than 50% of the world’s population and is one of the most important crops in the world. To evaluate the variation between different rice classfications, genetic diversity amoung a diverse set of rice collection including 59 breedlines, 23 landraces, 18 weedy rices and 35 introductions were analysed using 134 SSR markers located on the 12 chromosomes. In total, 1269 alleles were identified with an average of 9.47 per locus. Of the 1269 alleles, 460 (36.2%) were common, with a frequency of 0.05–0.5; 741 (58.4%) were rare (frequency < 0.05) and 68 (5.4%) were abundant (frequency > 0.5). A relatively high Polymophism information content (PIC) value was detected in landraces with smaller number of accessions than that of breedlines. Model-based structure analysis revealed the presence of six subpopulations, which was essentially consistent with the clustering based on genetic distance. One hundred and eight accessions (80.0%) showed a clear relation to each cluster based on their inferred ancestry value (>70%), while the remaining 27 accessions (15.4%) of which nine from landraces and fifteen from introductions were categorized as admixtures. Landrace and introductions distributed to almost all the six subpopulations whereas most of breedlines distributed to two distinct subpopulations. In conculusion, landraces in the present study showed critical importance in preservation of genetic diversity and rice breeding programs.