We generated 55 introgression lines via backcrosses using Milyang23 as the recurrent parent and Oryza glaberrima as the donor. 141 SSR markers were used to genotype 55 introgression lines. The 55 introgression lines with Milyang23 were evaluated for physiological traits; fresh shoot weight (FSW), fresh root weight (FRW) and dry shoot weight (DSW) under the control and 30% PEG-treated condition. Three lines showing significant difference with Milyang23 were selected for further analysis. Three lines had four, four and two O. glaberrima homozygous segments, respectively. IL9 performed better than Milyang23 in all traits measured in the 30% PEG-treated condition. IL9 possessed four O. glaberrima introgressions on chromosomes 1, 2, 6 and 7. IL12 performed better than Milyang23 in FSW and FRW. IL55 contains two O. glaberrima introgressions on chromosomes 2 and 6. Three lines shared the O. glaberrima segment delimited by markers RM133-RM225 at chromosomes 6. This region corresponds to the QTL region for drought tolerance reported by other previous studies. Although IL9 and IL12 showed improved drought tolerance at the seedling and vegetative stage, they performed poor under the drought stress at the reproductive stage implying that the level of drought tolerance differs according to the growth stage in rice. IL55 had significantly higher no. of the total grain than Milyang 23. This result seems to indicate that IL55 will be a good resource for drought tolerance breeding. The population would be useful in developing drought tolerant lines in the breeding program.

Rice blast is one of the major threats to stable rice production. In modernized rice breeding system, development of rice cultivars harboring resistance gene is one of the most efficient approaches against blast disease. Wild rice species, to the context, have been recognized as valuable genetic resources in improving resistance or tolerance level of modern commercial rice cultivars against biotic or abiotic stresses. National Institute of Crop Science (NICS), Korea developed an introgression line, ‘Suweon 506’, which has inherited the rice blast resistance from a BBCC genome wild Oryza species, O. minuta (Acc. 101141). Genetic analysis was carried out to localize the chromosomal region responsible for the rice blast resistance of ‘Suweon 506’ by using F2 progenies from ‘Suweon 506’ × ‘Milyang 23’. Association analysis between marker genotypes and their inferred resistance levels of F2 progenies against a Korean blast isolate, ‘93-072’ localized the target genetic region on rice chromosome 12. Further association analysis with increased number of DNA markers, and e-Landings on the rice pseudomolecule 6, the segment of ‘RM101-S10704-RM1337’ was identified to be tightly linked to the rice blast resistance gene from O. minuta at the 8.8~11.9 Mbp physical region of rice chromosome 12, where at least 9 rice blast resistance genes have been also identified. The 3.1 Mb equivalent virtual contig, composed with 31 BAC/PAC clones will be further analyzed for fine mapping and gene identification.