• Journal of Crop Science and Biotechnology
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• v.10 no.3
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• pp.175-184
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• 2007

Two subspecies, japonica and indica, have been reported in rice, which differ in several ecotypic traits. However, reproductive barriers in hybrid progenies between subspecies have been major obstacles in breeding programs using inter-subspecific hybridization. As the first step to elucidate the reproductive barriers, we developed subspecies-specific(SS) STS markers in this study. A total of 765 STS primers were designed through comparing DNA sequences at every $2{\sim}3$cM interval between japonica and indica rices, which are available at Web DBs such as IRGSP, NCBI, TIGR, and GRAMENE, and tested for subspecies-specificity using 15 indica and 15 japonica varieties of diverse origin. Of them, 67 STS markers were identified as SS STS markers and their subspecies-specificity scores were estimated. The SS markers were dispersed throughout the genome along chromosomes. Of them, 64 SS markers were mapped on an RIL population derived from a Dasanbyeo(indica)/TR22183(japonica) cross. Genomic inclination of RILs was evaluated based on the genotyping with different types of markers. Association test between markers and segregation distortion revealed that segregation distortion might not be the cause of generating SS markers. The SS markers will be applicable to estimate the genomic inclination of varieties or lines and to study the differentiation of indica and japonica, and ultimately to breed true hybrid rice varieties in which desirable characters from both subspecies are recombined.

• Korean Journal of Breeding Science
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• v.41 no.2
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• pp.101-105
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• 2009

Rice (Oryza sativa L.), the world's most important crop, is usually classified into ssp. indica and japonica based on morpho-physiological traits. In the previous study, we have developed subspecies-specific STS markers (SS markers) to readily discriminate between indica and japonica in O. sativa. In this study, we employed SS markers to investigate the genomic inclination of worldwide collections of O. sativa. A total of 320 varieties were divided into two groups with 63 SS markers. Namely, they formed two distinctive groups, indica and japonica, as expected by their geographic origin. The population structure analysis revealed that the variability of genetic background was greater in indica than in japonica. Some of them, however, exhibited intermediate genomic inclination between indica and japonica. These results are in general agreement with the previous studies, suggesting that SS markers are powerful tools for both determination of subspecies genome and assessment of genetic diversity in rice.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.04a
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• pp.110-110
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• 2022

Rice is the world's most important food crop and a major source of nutrition for about two thirds of populations. Northern Vietnam is one of the most important centers of genetic diversity for cultivated rice. In this study, we determined the genetic diversity and population structure of 79 rice landraces collected from northern Vietnam and 19 rice accessions collected from different countries. In total, 98 rice accessions could be differentiated into japonica and indica with moderate genetic diversity and a polymorphism information content of 0.382. We also detected subspecies-specific markers to classify rice (Oryza sativa L.) into indica and japonica. Additionally, we detected five marker-trait associations and rare alleles that can be applied in future breeding programs. Most interestingly, analysis of molecular variance (AMOVA) found genetic differentiation was related to geographical regions with an overall PhiPT (analog of fixation index FST) value of 0.130. More emphasis was given to provide signatures and infer explanations about the role of geographical isolation and environmental heterogeneity in genetic differentiation among regions in landraces from northern Vietnam. Our results suggest that rice landraces in northern Vietnam have a dynamic genetic system that can create different levels of genetic differentiation among regions, but also maintain a balanced genetic diversity between regions.