Jin-Chul Shin

Quantitative trait loci for cold tolerance of rice recombinant inbred lines in low temperature environments

Low temperature is one of the major environmental stresses in rice cultivation in high-altitude and high-latitude regions. In this study, we cultivated a set of recombinant inbred lines (RIL) derived from Dasanbyeo (indica) / TR22183 (japonica) crosses in Yanji (high-latitude area), Kunming (high-altitude area), Chuncheon (cold water irrigation) and Suwon (normal) to evaluate the main effects of quantitative trait loci (QTL) and epistatic QTL (E-QTL) with regard to their interactions with environments for coldrelated traits. Six QTLs for spikelet fertility (SF) were identified in three cold treatment locations. Among them, four QTLs on chromosomes 2, 7, 8, and 10 were validated by several near isogenic lines (NILs) under cold treatment in Chuncheon. A total of 57 QTLs and 76 E-QTLs for nine cold-related traits were identified as distributing on all 12 chromosomes; among them, 19 QTLs and E-QTLs showed significant interactions of QTLs and environments (QEIs). The total phenotypic variation explained by each trait ranged from 13.2 to 29.1% in QTLs, 10.6 to 29.0% in EQTLs, 2.2 to 8.8% in QEIs and 1.0% to 7.7% in E-QTL × environment interactions (E-QEIs). These results demonstrate that epistatic effects and QEIs are important properties of QTL parameters for cold tolerance at the reproductive stage. In order to develop cold tolerant varieties adaptable to wide-ranges of cold stress, a strategy facilitating marker-assisted selection (MAS) is being adopted to accumulate QTLs identified from different environments.

Importance of National Crop Productivity in View of CO 2 Balance

Crop production in a country is very crucial not only in a country`s crop self-sufficiency, but also in carbon recycle. Crop can capture and store the emitted by cereal food consumption. However, imported cereal food is not concerned in carbon recycle and this hinders the accurate estimation of carbon recycle. Korea imports major grain products including wheat, corn, soybean, and rice and about 90% of the grain composition consists of carbohydrate, protein and lipid. Carbon portions in carbohydrate, protein and lipid are 45, 53, and 77%, respectively. When the carbon portions are digested and converted into completely, one ton of rice, wheat, corn, and soybean can release 1.51, 1.63, 1.56, and 1.56 tons of to the atmopshere, respectively. Based on this premise, the evolved calculated from imported grains for the last 4 years in Korea was over 21 MT of . This amount is equivalent to 4.8 billion US dollars in the conception of carbon tax. These results suggest that a decrease in a cereal import(i.e, an increase in a country`s crop self-sufficiency) can lower release to the atmosphere.

Leaf Senescence in a Stay-Green Rice Variety, SNU-SG1 and a Mutant, sgr

During leaf senescence, the most characteristic visible change is leaf yellowing due to the preferential breakdown of chlorophyll (Chl) with concomitant chloroplast degradation. In this study, we examined the characteristics for the staygreenness during dark-induced senescence (DIS) in two stay-green varieties, SNU-SG1 and sgr;. During DIS, Chl loss was delayed in SNU-SG1 and sgr; compared with that in wild type (WT), but the photochemical efficiency of PSII (Fv/Fm) was not. The content of the functional PSII during DIS, estimated as (1/Fo 1/Fm) was high in WT, but low in SNU-SG1 and sgr;. In both varieties, Fo parameter increased during DIS, indicating the detachment of LHCII in PSII. In western blot analysis, the D1 and LHCII of WT were detected even when leaves turned yellowed. However, D1 protein in sgr; completely disappeared after 2 days without significant decrease in LHCII. These results suggest that both of the SNU-SG1 variety and sgr; mutant are non-functional stay-green species and largely attributed to the high stability of LHCII with an early degradation of D1 protein as a key protein of PSII.