• KOREAN JOURNAL OF CROP SCIENCE
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• v.66 no.1
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• pp.8-17
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• 2021

As rice originates from tropical regions, low temperature stress during the germination stage in temperate regions leads to serious problems inhibiting germination and seedling establishment. Identifying and characterizing quantitative trait loci (QTLs) for low-temperature germination (LTG) resistance help accelerate the development of rice cultivars with LTG tolerance. In this study, we identified QTLs for LTG tolerance (qLTG5, qLTG9) and germination coefficient of velocity under optimal conditions (OGCV) (qOGCV7, qOGCV9) using 129 recombinant inbred lines (RILs) derived from the cross between a low-temperature sensitive line Milyang23 and a low-temperature tolerant variety Gihobyeo. qLTG9 and qOGCV9 were detected at the same location on chromosome 9. At both LTG QTLs (qLTG5 and qLTG9), the alleles for LTG tolerance were contributed by the japonica variety Gihobyeo. At qOGCV7 and qOGCV9, the alleles for low temperature tolerance were derived from Milyang23 and Gihobyeo, respectively. The RILs with desirable alleles at two or more QTLs, i.e., GroupVII: qLTG5+qLTG9 (qOGCV9) and GroupVIII: qLTG5+qOGCV7+qLTG9 (qOGCV9), showed stable tolerance under low-temperature stress. Our results are expected to contribute to the improvement of tolerance to low-temperature and anaerobic stress in japonica rice, which would lead to the wide adoption of direct-seeding practices.

• Journal of Practical Agriculture & Fisheries Research
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• v.24 no.3
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• pp.25-31
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• 2022

Low-temperature germinability (LTG) is an important trait for the direct seeding of rice in temperate and high altitudes regions. Water temperature of rice fields at sowing season is frequently under 15℃ in Korea, resulting in poor seedlings establishment. The objective of this study was to phenotypically and genetically evaluate 600 rice germplasm composed of six rice subpopulations. In the phenotypic evaluation, aus (AUS) showed the highest visual rating (VR) and germination rate (GR) of 5 and 83.1%, respectively, than other subpopulations. The lowest value of VR (7.1) and GR (53.1%) was observed in aromatic (ARO) subpopulation. Association of the phenotype for LTG with the genotype for qLTG3-1, a major QTL for LTG, and other three SNP markers (LTG_8, qLTG4b-1, qLTG2-6) was conducted. The results suggested that the allele distribution of two markers, qLTG3-1 and qLTG2-6, affects the difference in VR and GR between subpopulations. qLTG4b-1 and LTG_8 were also highly significant with LTG in all subpopulations except that qLTG4b-1 did now show significance in AUS. Therefore, the combination use of these four markers might be effective for evaluation of LTG in rice germplasm.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.116-116
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• 2017

Low-temperature is one of the environmental stress factors that affect plant growth and development and consequently limit crop productivity. The control of seed germination under low-temperature is organized by many genes which are called quantitative trait loci (QTLs). High germination rate for low-temperature is an important factor of growing rice. Previously, we identified a major QTL controlling low-temperature germinability in rice using 96 introgression lines (ILs) derived from a cross between Oryza rufipogon (Rufi) and the Korean japonica cultivar, 'Hwaseongbyeo (HS)'. A $BC_3F_7$ line (TR5) showed better low-temperature germinability than its recurrent parent. TR5 was crossed with HS to develop a segregating F2:3 populations for the target QTL. Six SSR markers polymorphic between HS and Rufi were used to screen and fine map the qLTG1. The qLTG1 on chromosome 1, which accounted for 55.5% of the total phenotypic variation, confirmed that Rufi allele enhanced the low-temperature germinability. Intervals between markers CRM16 and CRM15, four candidate genes were identified. The identified candidate genes, which are encoded by a protein of unknown function, showed their direct involvement on seed germination at low-temperature. To identify genes targeted by qLTG1, we investigated the expression profiles of these candidate genes and germination behavior of qLTG1 under different stress conditions and compared to HS, Rufi, and TR5 at $13{\pm}2^{\circ}C$ for 3 days after incubation. Furthermore, transgenic rice plants will also be developed to conduct a detailed investigation on low-temperature germinability. Hence, the QTL for low-temperature germinability would be useful in rice breeding programs especially in the development of lines possessing low-temperature germinability.