벼멸구에 감수성이며 고품질인 ‘황금누리’와 벼멸구 저항성 유전자 Bph18을 가지고 있는 SR30071-3-7-23-6-1-1-1계통을 교배하여 전통육종법과 분자육종법을 활용하여 새로운 벼멸구 저항성 계통을 선발하여 병해충 저항성과 농업형질을 조사 수행하였다. 1. 20개체의 F1을 양성하여 F2 1,200개체를 포장에 전개하 였다. 포장에서 선발된 개체에 대해 실내미질선발을 수행하여 23개체의 F3를 공시하였으며 벼멸구 유묘검정, 도열병 밭못자 리검정, 흰잎마름병 K1 균계 접종검정을 실시한 후 F4 세대 를 거쳐 100계통을 F5 세대로 공시하였다. 2. F5 세대에서 DNA 마커 검정으로 100계통 중 Bph18은 92계통, Xa3는 96계통, Stv-bi는 98계통에서 저항성 유전자가 확인되었다. 생물검정에서는 100계통 중 벼멸구 유묘검정은 94계통이 저항성을, 흰잎마름병 K3 균계검정은 27계통 및 73 계통이 각각 저항성 및 중도저항성 반응을 보였다. 3. F5 세대 100계통 중 주요 농업적 형질이 우수한 11계통 을 생산력검정시험에 공시하였고, 보통기 보비재배에서 농업 형질이 양호하고, 수량이 높으며 병해충 저항성을 보이는 우 량한 4계통을 선발하여 이삭모양과 초형이 우수하며 출수기는 중만생종이며, 간장이 작고 수량이 높은 HR28011-1-2-3을 ‘익 산562호’로 계통명을 부여하였다. 본 실험에서 육성한 ‘익산562호’는 지역적응성 평가를 통한 품종화를 추진 중이며 벼멸구 및 기타 주요 병해충에 복합저 항성 벼품종육성을 위한 유전자원으로 활용되기를 기대한다.

To diversify the grain size and shape of japonica rice, we developed the Breeding Materials with Diverse Grain Size and Shape (BM_DGS) and characterized the grain and yield-related traits. We used the donor parents Jizi1560 and Jizi1581, japonica germplasm with extremely large grain size. Four cross combinations between the each donor parents and Korean high yielding japonica rice cultivars, Deuraechan and Boramchan, were constructed and anther culture method was applied. Among 290 doubled haploid lines, we selected 91 elite lines with diverse grain size and shape and designated to the BM_DGS. The grain size and shape of BM_DGS exhibited beyond the characteristics of previously developed Korean rice cultivars. The alleles of major grain-related genes, GW2, GS3, and qSW5, in BM_DGS showed two types, wild type or loss-of-function mutant type. The loss-of-function mutant alleles, gw2, gs3, and qsw5, had an effect on increasing grain size. The phenotypic variation of grain length was mostly controlled by GS3 alleles, and grain width and thickness were influenced by the combinations of GW2 and qSW5 alleles. 1,000-grain weight was determined by the combinations of GW2, GS3, and qSW5. The grain-related genes influenced the phenotypic variation of yield-related traits. The result of this study could be useful to elucidate the relationship between the grain-related genes and agronomic traits. And the BM_DGS are being utilized in the breeding programs to diversify the grain size and shape in japonica rice.

Four bacterial blight resistance genes, Xa1+Xa3+xa5+Xa21, pyramid elite japonica rice lines were developed for enhancing the resistance of rice against Xanthomonas oryzae pv. oryzae in Korea. Seven doubled haploid (RDL1-7) and ten F6 lines (RPL1-10) having Xa1+Xa3+xa5+Xa21 which were derived from the cross between Ilmi, high grain quality japonica rice cultivar carrying Xa1, and Iksan575, elite line carrying Xa3+xa5+Xa21, were developed using marker-assisted selection for resistance genes and phenotypic selection for bacterial blight resistance and agronomic traits. Among resistance genes combinations in F2 population, four resistance genes combination, Xa1+Xa3+xa5+Xa21, showed the highest resistance and conferred the enhanced resistance than three genes combination, Xa3+xa5+Xa21. Four genes pyramid lines (RDL and RPL) showed broad-spectrum resistant against 16 Korean bacterial blight isolates and the yield and quality of the lines did not alter by the inoculation of K3a, the most virulent race in Korea. In addition, these lines had excellent plant type and exhibited more enhanced yield than previously developed resistant cultivars. Four bacterial blight resistance genes combination, Xa1+Xa3+xa5+Xa21, was efficient and promising combination and developed lines with four genes could be useful materials and will be applied to the breeding programs for enhancing the resistance of japonica rice against bacterial blight.

This study was conducted to identify quantitative trait loci (QTL) related to grain qualities under high temperature during ripening stage using 187 Korean rice varieties. To analyze grain qualities under high temperature during ripening stage, grain appearance such as head rice and chalky grains percentage and physicochemical characteristics were investigated and SNP genotyping of 187 Korean varieties was conducted for association analysis related with grain qualities under high temperature. Five traits exhibited continuous distributions in the non-glutinous Korean varieties, indicating that these traits are controlled by multiple genes. Association mapping among non-glutinous Korean varieties was conducted using 223 markers showed polymorphism among 384 SNP markers. Six QTLs for chalk grains percentage were mapped to chromosomes 1, 4, 10 and 11. These six QTLs were linked to the SNP marker id1014176 on chromosome 1, id4010924 on chromosome 4, id10000644 on chromosome 10 and id11011505 on chromosome 11, and explained approximately 21, 61, 50, 23, 23 and 21% of the total phenotypic variance. Four QTLs for head rice percentage in chromosomes 4, 10 explained the total phenotypic variance by over 47% and around 20%. Fifteen QTLs for RVA characteristics including hot paste viscosity, peak viscosity and setback viscosity were mapped to chromosome 1, 6, 7, 12 and QTLs were explained around 20% of the total phenotypic variance.

Japonica rice cultivars exhibit high susceptibility to bacterial blight(BB) disease due to genetic vulnerability in Korea. Korean japonica resistant rice cultivars mainly possess one of the genes, Xa1 or Xa3 for BB resistance. These resistance genes are becoming susceptible to K3a, resulting in serious rice yield reduction. This study was carried out to confirm the effect of xa13 gene pyramiding for developing of japonica rice cultivars resistant to BB pathogen breaking down Xa1 or Xa3. IRBB4 conferring Xa4 gene was resistant to K1(HB01013), K2(HB01014), K3(HB01015), and moderately resistant to K3a(HB01009). IRBB5 having xa5 gene was resistant to K1, K2, K3, and K3a. The recessive gene xa13 was resistant to K1 race but susceptible to K2, K3, and K3a. But Xa21 gene is susceptible to predominant K1 race but resistant to other races such as K2, K3, and K3a. Two genes Xa3 and xa13 were susceptible and Xa4 gene was moderate resistant to 24 isolates. xa5 and Xa21 genes were resistant to all isolates including K3a. When xa13 gene combined Xa4, xa5 and Xa21 genes, effect of xa13 gene pyramiding showed higher resistant reaction than that having singe gene out of Xa4, xa5, and Xa21. The order of resistance against 24 isolates breaking down Xa3 gene was IRBB55(xa13+Xa21) > IRBB53 (xa5+xa13) > IRBB51 (Xa4+xa13).