Rice cultivation by direct seeding allows reduced labour and production costs in addition to other benefits. However the success of this rice production method can be limited by uneven fields with poor drainage or heavy rainfall at sowing leading to early flooding conditions slowing germination and hindering crop establishment. Hence, the need to improve tolerance to anaerobic conditions in both rainfed and irrigated rice ecosystem after direct seeding. In this study QTL analysis was performed to identify QTLs associated with tolerance derived from Vietnamese variety Tai Nguyen (TN) under anaerobic conditions during germination. The population derived from a cross between TN (tolerance indica lines) and Anda (susceptible japonica), was used for collection of phenotypic data based on the survival rates of the seedlings at 21 days after sowing under 10cm of water. A total of 286 F2:3 families of the population were used for QTL mapping and the genotyping was carried out with the infinium 6K SNP-chip based on the illumina infinium platform. Two significant QTLs associated with the AG trait were detected on chromosomes 1 and 11, respectively. In Particular, the QTL on chromsome 1 had an LOD score of 7.45 and R2 of 14.21%. We plan to confirm the identified QTLs in further studies and develop varieties with improved anaerobic germination ability using advanced backcross lines.

Bacterial blight (BB) of rice, caused by Xanthomonas oryzae pv. oryzae (Xoo), is a significant disease in most rice cultivation areas. The present study was performed to identify new BB R-gene conferring resistance to Korea Xoo isolates, derived from IR65482-7-216-1-2 and to construct a physical map of the candidate gene. An F2 population derived from a cross between 11325 and Anda was used to determine the exact position of the nearest recombination event to the target region. The position of the R-gene was delimited by flanking markers, RM1233 and RM5766, on chromosome 11. Of the 56 markers designed in the flanking region, 20 were selected as anchor markers and the R-gene was mapped to a 295kb region on chromosome 11. To narrow down the interval spanning the R-gene, an additionally SSR marker, 20 STS markers, and CAPS marker between RM27320 and ID55.05-79 were developed using rice reference genome information. From the result the gene was defined by RM27320 and ID55.WA18-5 located in the BAC clone OSJNBa0036K13. The physical distance between these two markers is approximately 80kb. In a further study, gene expression analysis against listed candidate genes was investigated using semi-quantitative transcription PCR. These results will useful for future disease breeding as well as gene function studies regarding resistance genes.