본 연구에서는 밀양23호의 배경에 O. glaberrima의 특정 염색체단편을 가지는 55 이입계통의 내건성 관련 형질을 조 사하여 변이를 검정하고 내건성이 향상된 4 계통을 선발하였 다. 특히 IL55는 유묘기, 영양생장기 그리고 생식생장기에서 반복친인 밀양23호에 비해 조사된 내건성 형질에서 우수한 특성을 보였으며 내건성 관련 유전자의 분석 및 교배모본으 로 이용될 수 있을 것이다. 이입계통들은 밀양23호의 유전적 배경에 각 계통마다 서로 다른 O. glaberrima 단편이 이입된 계통으로, 이 집단은 O. glaberrima에서 유래된 내재해성 및 작물학적으로 유용한 유전자의 탐색에 효율적인 도구가 될 것이다.

Drought stress is one of the major stress affecting growth and productivity in rice. Drought tolerance is a complex trait governed by quantitative trait loci (QTLs) making it difficult to understand mechanisms underlying it. We generated a set of 55 introgression lines via a backcrossing using Milyang23, a Korean Tongil-type rice variety as the recurrent parent and O. glaberrima (IRGC Acc. No. 103544), an exotic collection from Mali, West Africa as donor parent. 141 SSR markers were used to genotype 55 introgression lines. The 55 introgression lines with the Milyang23 were evaluated for physiological traits such as Fresh shoot weight (FSW), Fresh root weight (FRW) and Dry shoot weight (DSW) under control and 20% PEG-treated condition. Three lines (IL9, 12, 55) showing significant difference with Milyang23 were selected. The genetic background of the three lines were similar to Milyang23 and it has four, four and two O. glaberrima homozygous segments, respectively. IL9 performed better than Milyang23 in all traits measured in the 20% 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. IL12 contains four O. glaberrima introgressions on chromosomes 3 and 6. And IL55 contains two O. glaberrima introgressions on chromosomes 2 and 6. O. glaberrima segment delimited by markers OSR19-RM225 at chromosomes 6 was commonly present in these three lines. This region corresponds to the QTL region for drought tolerance reported by other previous studies. A set of introgression lines are being developed containing only few chromosomal segments from O. glaberrima in the Milyang23 background. These would be useful not only in developing drought tolerant lines in the breeding program but also in fine-mapping the genes/QTLs for drought resistance.

Using a series of BC8F4 nearly isogenic lines(IL-20) derived from a cross between Hwaseongbyeo, as the recurrent parent, and wild rice Oryza minuta (IRGC Acc. No. 101144) as the donor parent we constructed a high-resolution physical map for the days to heading (dth9)-QTL. dth9 QTL was mapped to the long arm of chromosome 9 across a 34.74-kb region containing 8 predicted genes. Heading date of Japonica rice variety Hwaseongbyeo was one week earlier than a near-isogenic line (NILs) IL-20 under natural field (NF) conditions and 3-4 days under short-day (SD) conditions implying that the dth9-QTL is involved in photoperiod sensitivity in rice. Of the 8 predicted genes three were protein-coding genes in dth9-QTL region. According to RiceXpro published data, micro-array analysis of different leaf developmental stages of Nipponbare showed a higher level of LOC_Os09g36700 mRNA expression during panicle initiation stage. This data further supported our prediction that dth9 locus is responsible for delayed heading in IL-20. Previous studies showed that RNase T2 family proteins are involved in photoperiod sensitivity. Based on these findings we sequenced two candidate genes, which encoded for RNase T2 family proteins. Interestingly, we found the existence of a missense mutation in LOC_Os09g36700 gene suggesting that dth9-QTL might control difference in days to heading between Hwaseongbyeo and IL-20. The QTL for days to heading had not been detected in previous QTL studies between Oryza cultivars, indicating the existence of potentially novel allele from O. mimuta.