수발아는 등숙기간 중 고온, 다습 또는 강우에 의해 종종 발생하여 미질과 수량 감소를 야기한다. 일반적으로 자포니카 품종이 인디카 품종보다 수발아가 잘되는 경향이 있어 고온다습한 열대지역에 적응하는 재해안전성 품종육성의 기초자료를 제공하고자 현재 개발되어 있는 열대지역 적응 자포니카 품종인 ‘MS11’, ‘Japonica1’, ‘Japonica2’의 수발아 특성을 조사한 결과를 요약하면 다음과 같다. 1. 자포니카형 품종인 ‘MS11’, ‘Japonica1’, ‘Japonica2’가 열대 및 온대지역과 상관없이 통일형인 ‘세계진미’, 인디카형 품종인 ‘IR72’보다 대체적으로 수발아율이 높았다. 2. ‘MS11’과 ‘Japonica1’의 수발아율은 편친인 ‘진미’보다 낮아 수발아 저항성이 향상되었음을 확인하였다. 3. ‘MS11’은 대체적으로 열대 및 온대지역 모두에서 수발아율이 낮은 반면에 ‘Japonica2’는 두 지역 모두에서 높은 수발아율을 보여 고온다습한 열대지역 보급에 지장이 있을 것으로 판단되었다.

Eating and cooking qualities are the most important trait in japonica rice breeding program in Korea. More improvements in grain quality to meet the demand of consumers are needed to develop new rice germplasm of high grain quality. In this study, we performed genetic analysis and grain quality evaluation in 96 Korean japonica rice germplasm including 26 varieties with 4 Japanese japonica high eating quality, 24 landraces, 22 weedy rices, and 14 breeding lines. These germplasm were analyzed using 13 DNA markers related to eating quality to conjecture the palatability of cooked rice (Lestari et al. 2009). Most varieties of high eating quality were clustered with germplasm of high expected quality (eq) varieties of similar genetic background of pedigree. The expected quality (eq) values of high eating quality varieties, Gopum, Ilpum, Samgwang, and Sugwang were 99.6∼104.5, and Koshihikari was 103.5. The eq of two weedy rices, Hoengseongaengmi 3 and Namjejuaengmi 6 were 101.9 and 101.6, respectively. However, Haiami of high eating quality was clustered with 15 weedy rice and 11 landrace germplasm of low eq value. The eq values of Haiami and Wandoaengmi 6 were 66.9 and 40.8, respectively, but they has 2 and 3 of palatability of cooked rice, and 73.6 and 78.6 of glossiness of cooked rice, respectively. We expect these germplasm would be new source for rice grain quality to develop japonica rice of high eating quality.

Tongil (IR667-98-1-2) rice, developed in 1972, is a high-yielding rice variety derived from a three-way cross between indica and japonica. Tongil contributed to staple food self-sufficiency of Korea, an achievement that was termed the ‘Korean Green Revolution’. In this study, we analyzed the nucleotide-level genome structure of Tongil rice and compared it to those of the parental varieties. A total of 17.3 billion Illumina Hiseq reads, 47× genome coverage, were generated from Tongil rice. Three parental accessions, two indica and one japonica types, of Tongil rice were also sequenced for approximately 30x genome coverage. A total of 2,149,991 SNPs were detected between Tongil and Nipponbare; the average SNP frequency of Tongil was 5.77 per kb. Genome composition based on the SNP data by comparing with the three parental genome sequences on sliding window of Nipponbare genome sequence revealed that 91.8% of the Tongil genome originated from the indica parents and 7.9% from the japonica parent, different from the theoretical expectation in a three-way cross, i.e., 75% indica and 25% japonica parental origins on average. Copy number of SSR motifs, ORF gene distribution throughout the whole genome, gene ontology (GO) annotation, yield-related QTLs or gene locations, and polymorphic transposon insertions were also comparatively analyzed between Tongil and parents using sequence-based tools. The results indicated that each genetic factor was transferred from parents into Tongil in proportion to the whole-genome composition. The Tongil rice is the first successful superior cultivar derived from indica × japonica hybridization in Korea. Defining of genome structure demonstrates that the Tongil genome is composed mostly of the indica genome with a small proportion of japonica genome introgression. This work was supported by a grant from the Next-Generation BioGreen 21 Program (Plant Molecular Breeding Center No. PJ008125), Rural Development Administration, Republic of Korea.

Fifty-two Korean japonica rice cultivars were analyzed for leaf blast resistance and genotyped with 4 STS and 26 SSR markers flanking the specific chromosome sites linked with blast resistance genes. In our analysis of resistance genes in 52 japonica cultivars using STS markers tightly linked to Pib, Pita, Pi5(t) and Pi9(t), the blast nursery reaction of the cultivars possessing the each four major genes were not identical to that of the differential lines. Eight of the 26 SSR markers were associated with resistant phenotypes against the isolates of blast nursery as well as the specific Korean blast isolates, 90-008 (KI-1113), 03-177 (KJ-105). These markers were linked to Pit, Pish, Pib, Pi5(t), Piz, Pia, Pik, Pi18, Pita and Pi25(t) resistance gene loci. Three of the eight SSR markers, MRG5836, RM224 and RM7102 only showed significantly associated with the phenotypes of blast nursery test for two consecutive years. These three SSR markers also could distinguish between resistant and susceptible japonica cultivars. These results demonstrate the usefulness of marker-assisted selection and genotypic monitoring for blast resistance of rice in blast breeding programs.