It is well known that Dharial (Bangladesh origin and weedy rice line) has longer seed longevity than indica and japonica rice varieties. To study the genetic basis of seed longevity of Dharial, we developed 240 BC3F7 backcross recombinant inbred lines derived from the crosses between Dharial (a donor parent) and two korea rice accessions (recurrent parents) including Ilmi and Gopum, respectively. Among these lines, we selected two introgression lines with longer seed longevity and named them Ilmi-NIL and Gopum-NIL. Also, we developed an EMS-induced mutant line from Dharial which has shortened seed longevity, and named it Dharial-EMS. We performed re-sequencing of four rice accessions that are Dharial, Dharial-EMS, Ilmi-NIL, and Gopum-NIL. A total of 706×106 raw reads were generated which provided sequence data over 46x rice genome coverage per each accession. We did genome-wide variation analysis comparing produced re-sequencing data and the re-sequencing data of Ilmi from NABIC database with the Nipponbare reference sequence. By graphical analysis of SNP distribution in rice genome of the five accessions, we could select candidate chromosomal segments introgressed from Dharial in Ilmi-NIL and Gopum-NIL. The introgressed chromosomal segments were in seven regions in Ilmi-NIL and eight regions in Gopum-NIL, and four common introgressed regions between Ilmi-NIL and Gopum-NIL were identified. 2,758 SNPs between Dharial and Dharial-EMS were found in the introgressed regions. Also, we detected 450 genes including at least one SNP among these SNPs. This result will facilitate identification of genes and development of molecular markers for improvement of seed longevity.

In rice, tillering is an important trait determining yield. To study tillering at the agricultural and molecular aspects, we have examined a spontaneous rice mutant that showed reduction in the number of culms. The mutant was derived from a F6 line of the cross of Junambyeo*4 / IR72. It could produce, on average, 4 tillers per hill in the paddy field while wild-type plants usually have 15. Except the reduced culm numbers, they also show pale green phenotypes. The phenotypes of this mutant were co-segregated as the monogenic Mendelian ratio (χ2 = 0.002, p = 0.969). In order to locate a gene responsible for the rcn phenotype, the mutant with the japonica genetic background was crossed with Milyang21 of the indica background. Bulked segregant analysis was used for rapid determination of chromosomal location. Three SSR markers (RM551, RM8213, and RM16467) on chromosome 4 were genetically associated with the mutant phenotype. Each of the 217 F2 plants was genotyped with simple sequence length polymorphisms. The data showed that RM16572 on chromosome 4 was the closest marker that showed perfect co-segregation among the F2 population. We suggest the new rcn gene studied here name as rcn10t because there was no report which exhibit a rcn phenotype with a pleiotropic effect of pale green (chlorophyll deficiency), and mapped at same position on chromosome 4.

It is important to understand pedigree of rice cultivars commonly used for breeding. In this paper, pedigree tables for tracking the pedigree of 17 representative rice cultivars recommended by Rural development Adminstration (RDA) were completed and analyzed using two kinds of web database system; 'IRIS' and 'RRDB'. Seven cultivars, namely, 'Sangmibyeo', 'Ilpumbyeo', 'Saegewhabyeo', 'Surabyeo', 'Shindongjinbyeo', 'Ilmibyeo' and 'Jungwhabyeo' had 'Koshihikari' on the pedigree of their ancestor. Besides 'Koshihikari', the most feguently used ancestral germplasms among the high quality rice cultivars were 'Fujisaka 5', 'Kameno o' and 'Asahi', 'Fujisaka 5' was used as ancestral parent in 12 out of 17 cultivars. Interestingly, 'Kameno o' was used in pedigree of 16 out of 17 high quality varieties and 'Asahi' was used in the ancestral pedigree of all 17 varieties. 'Hwayeongbyeo' was used as one of parent in the breeding of 'Dongjin 1', 'Hwabongbyeo', 'Saegewhabyeo' and 'Junambyeo'. 'Ilpumbyeo' was used in the breeding pathway of 'Junambyeo' and 'Saegewhabyeo', 'Mangeumbyeo' itself was not enlisted as one of high quality rice cultivars, but was used as a breeding parent of three high quality varieties, namely, 'Saegewhabyeo', 'Hwabongbyeo' and 'Nampyeongbyeo'. Incorporated with evaluation data, pedigree will provide a valuable chance to genealogical tracking of agronomic traits such as disease resistance, grain quality and etc.