Physicochemical Characteristics and QTL Mapping Associated with the Lipid Content of High-Lipid Rice

This study was conducted to examine the physicochemical characteristics and perform QTL mapping of genetic factors associated with the lipid content of rice. A rice strain with a high lipid content, “P31-2-2-2-B-B”, was developed from mutants of “Dongjin” created by T-DNA insertion. The lipid content of “P31-2-2-2-B-B” brown rice was 4.42% whereas that of the donor cultivar “Dongjin” was 2.56%. The total fatty acid content of the high-lipid mutant brown rice was 7.82% and that of “Dongjin” was 3.43%. The unsaturated fatty acid composition of the mutant brown rice was 2.73% oleic acid, 2.74% linoleic acid, and 0.34% linolenic acid. In contrast, the fatty acid composition of the donor cultivar “Dongjin” was 1.30% oleic acid and 0.99% linoleic acid. The percentage of unsaturated fatty acid to total fatty acid in the high-lipid mutant was higher (74.3%) than that of “Dongjin” (66.8%). Continuous frequency distribution and transgressive segregation of the lipid content were observed in the F3 family (seeds) derived from a cross between the high-lipid mutant “P31-2-2-2-B-B” and a tongil-type cultivar “Samgang”. This result implied that the lipid content was a quantitative trait controlled by a polygene. Additionally, the broad sense heritability of lipid content was estimated to be 89.6% based on analysis of the F3 seeds. A significant QTL, qRLC5, was identified on chromosome 5 with a LOD score of 2.37, and was flanked by 5007 and 5014. Results of the present study should be useful for improving rice nutritional quality through marker-assisted selection.

Functional Analysis for Rolling Leaf of Somaclonal Mutants in Rice (Oryza sativa L.)

This study was carried out to facilitate the functional analysis of rice genes. Some 297 insertion plants (1.7%) of the entire lines with the endogenous retrotransposon Tos17 were produced. Phenotypes of these plants in the S2 genera-tion were observed in the field according to different leaf types. Rolling leaf mutants showed thinner sclerenchyma-tous cells, defective arrangement of vascular bundles, and well-formed bulliform cells as compared to the parental cultivar. Two new copies of Tos17 were detected in the rolling leaf type. In the new leaf type, the copy number and activation of Tos12, 15 did not appear as ‘Ilpum’. Flanking sequence tag (FST) analysis of Tos17 in the rolling leaf mutant indicated that new copies of Tos17 were transposed on chromosomes 11 and 12. Annotated homologues of the tagging genes on chromosome 11 were arabinoxylan rabinofuranohydrolase isoenzyme AXAH-I and II. The tagging gene in chromosome 12 was highly correlated with 6 kinds of genes including a transcript regulated factor and a rough sheath 2-like protein. This rolling leaf and flanking sequence data will stimulate the functional analysis of rice genes.

Comparison and Analysis of QTLs, Epistatic Effects and QTLx Environment Interactions for Yield Traits Using DH and RILs Populations in Rice

Two genetic linkage maps, constructed by DH and RILs populations derived from the same parents, were carried out for the identification and comparison of QTLs controlling yield traits across different years in rice （Oryza sativa L.）. A total of 194 SSR and STS markers were used in two maps, of which 114 markers were same. The distribution of Samgang allele was higher in RILs population than it in DH population. Comparing with DH population, RILs population has more lines with higher yield and wider phenotypic transgressive segression for yield traits. Although most of QTLs for the same trait were different in two populations across different years, 8 QTLs （including gwp 11.1, spp5.1, spp 10.1, spp 11.2, ssrl. 1, ssrl 1.1, tgw9.1 and tgwl 1.1） were detected over 2 yr. It is important to note that pppl0.1, sppl0.1 and tgw9.1 were identified in two populations, while sppl 0.1 and tgw9.1 were simultaneity observed across different years. Epistatic effects were more important than additive effects for PPP, SPP, yield in DH population and TGW, yield in R/Ls population. Epistatic effects of DH and RILs populations were different on the same genetic background in the present study, which illuminated the QE interaction played an important role on epistatic effect. Identification and comparison of QTLs for yield traits in DH and RILs populations should provide various and more precise information. The QTLs identified in present study would be valuable in marker-assisted selection program for improving rice yield.

Effective Procedure for Development of EST-SSR Markers Using cDNA Library

The present study was conducted to develop EST-SSR markers using the cDNA library from rice plant. Total RNA extracted from the leaves of brown plant hopper resistance gene originated from a rice cultivar “Cheongcheong” and sensitive rice cultivar “Nakdong” were used to synthesize a cDNA library. As a result of analyzing the cDNA library, the 17 EST-SSR primer sets were developed. This study enables to provide effective marker assisted selection (MAS) methods on the selection of white-backed planthopper resistance gene originated from a rice plant more simply, quickly and precisely. Furthermore, using this marker’s advantage of deriving from cDNA, it is possible to identify the white-backed planthopper resistance gene. In addition, this study introduces a technique for construction of a cDNA library safely without using radioactivity.