우리나라의 절화국화는 국내 화훼작물 중 큰 비중을 차 지하고 있다. 수출 또한 2011년에는 2001년대비 약 1.9배 증가하였지만 생산단가 상승과 주변 경쟁국들과의 가격 경쟁력으로 수출농가가 어려움을 겪고 있다. 이를 극복하기 위해서는 소비자의 기회에 맞는 품종을 개발하 고 또한 고품질 국화를 생산하는 것이 필요하다. 국화 품 질을 저하시키는 요인 중 하나는 병해충 감염이며, 국화 흰녹병이 가장 심각한 피해를 주고 있다. 국화흰녹병 병 발생을 근절할 수 있는 근본적인 해결책은 저항성 품종 개발이지만 이는 많은 시간이 필요하기에 단기적 방법으 로 가시적으로 병징이 나타나기 이전에 국화흰녹병 감염 여부를 검정할 수 있는 기술을 개발한다면 병 발생 피 해를 최소화할 수 있을 것이다. 국화흰녹병 검정 기술 개 발을 위해 실험실 조건에서 이병주의 연중 생산이 필수 적이기에 이병주를 생산하는 시스템을 우선적으로 확립 하였다. 그리고 자체 생산한 이병주에서 증식된 병원균 의 담자포자의 형태적 특성 및 rDNA의 DNA 염기서열 분석 결과로 국화흰녹병균임을 입증하였다. 또한 국화흰 녹병균 유전체 정보를 이용하여 국화흰녹병균만을 검출 할 수 있는 유전자를 선발하였고 이 유전자를 대상으로 국화흰녹병균 게놈 DNA 0.25ng까지 검출할 수 있는 프 라이머 쌍을 개발하였다. 동일한 프라이머를 이용하여 Real-time PCR를 실시하면 게놈 DNA 6pg까지 검출이 가능하였다.향후 이러한 방법을 이용하여 병원균 접종후 육안으로 병징이 확인되기 이전에 국화흰녹병균의 검출 을 확인할 예정이다.

국화는 국내외적으로 주요 화훼작물이지만 국화 흰녹병은 안정적 생산에 큰 걸림돌이 되고 있다. 현재까지 국화 흰녹병 방제는 농약살포를 통한 화학적 방제와 다습한 재배환경을 개선하는 재배적 방제에 의존하고 있지만, 살균제 저항성을 갖는 새로운 병원균 출현으로 농약 살포를 통한 병 방제에는 한계가 있어 병 저항성 품종 개발이 절실하다. 흰녹병은 순활물기생균인 Puccinia horiana에 의해 발생하는 곰팡이 병으로 이로 인한 경제적 손실이 크지만, 다른 주요 작물병과 비교하여 상대적으로 연구가 미흡하다. 특히 병원균의 전파 경로와 병원성의 다양성(pathogenic diversity), 병원균 침입기작 및 기주식물과의 상호작용에 대한 전반적인 지식 부족으로 효과적 농약 살포 기준 설정과 병저항성 품종개발에 어려움이 있다. 따라서 본 논문에서는 이러한 과제를 해결하는데 기초자료를 제공하고자 각 연구분야별로 현재까지 발표된 연구결과를 정리하고 앞으로 요구되는 연구과제에 대하여 모색하여 보았다. 특히 효과적 약제처리 기준 설정과 병저항성 품종 개발의 출발점이 되는 흰녹병균의 생활사와 생태, 병원균 DNA 정보를 이용한 조기진단, 병원균의 병원형 등에 관해 현재까지의 연구결과들을 정리하였다. 앞으로 흰녹병균의 식물체 침입 기작에 관한 종합적 이해의 폭을 넓히고, 병원균 침입 시 식물체내에서 발병과 병저항성 유도 요인에 대한 분자 수준에서 연구가 진행된다면 흰녹병균 저항성 품종 육성 시기를 앞당길 수 있으리라 사료된다.

In order to breakthrough upcoming challenges for the food production, the efficient use of rice germplasm would be a indispensible. These rice germplasm, adapted from diverse eco-systems, are undiscovered treasures for rice breeders/researchers, potentially providing a broad array of useful alleles that enrich gene pools of current cultivated rice varieties. Although growing ex-situ conservation efforts are an important for preserving diverse rice genetic resources, the activity on finding the novel and favorable genetic variants from the vast genebank collection is greatly challenging, requiring extensive screening processes. Therefore, rice core collection is a powerful solution to accelerate utilizations of the exotic germplasm of the entire population. In addition, The application of whole genome re-sequencing technology would establish a potent platform for fast forward genetic study, such as genome wide association study (GWAS). The GWAS has been implemented to efficiently identify candidate genes related to various useful agricultural traits in many crop species including rice. Given the significant associations between genetic variations and phenotypic diversity does not require prior knowledge, GWAS using high genome coverage of SNP markers provides a genomics platform to dissect previously unknown adaptive or other useful genetic variation accumulated in plant germplasm resources over the times. Once pinpointing candidate genes, GWAS allows informed choice of parents for QTL analysis based on the haplotype information, along with suggesting targets for following mutagenesis and transgenics. Here, we are to report our current achievements and perspectives from GWAS and post-GWAS undertaken to dissect and exploit useful alleles underlying many agricultural traits from Rice core set, including PHS (Pre-Harvest Sprouting), salt tolerance and disease resistance and so forth. Also, we will introduce the integrated Omics based GWAS case study using transcriptomes, proteomes, metabolomes and ionomes of our rice core set.

A sugary mutant with low total starch and high sugar content was compared with its wild type Sindongjin for grain-filling caryopses. In the present study, developing seeds of Sindongjin and sugary mutant from the 11th day after flowering (DAF) were subjected to RNA sequencing (RNA-Seq). A total of 30,385 and 32,243 genes were identified in Sindongjin and sugary mutant. Transcriptomic changes analysis showed that 7,713 differentially expressed genes (DEGs) (log2 Fold change ≥1, false discovery rate (FDR) ≤ 0.001) were identified based on our RNA-Seq data, with 7,239 genes up-regulated and 474 down-regulated in the sugary mutant. A large number of DEGs were found related to metabolic, biosynthesis of secondary metabolites, plant-pathogen interaction, plant hormone signal transduction and starch/sugar metabolism. Detailed pathway dissection and quantitative real time PCR (qRT-PCR) demonstrated that most genes involved in sucrose to starch synthesis are up-regulated, whereas the expression of the ADP-glucose pyrophosphorylase small subunit (OsAGPS2b) catalyzing the first committed step of starch biosynthesis was specifically inhibited during the grain-filling stage in sugary mutant. Further analysis suggested that the OsAGPS2b is a considerable candidate gene responsible for phenotype of sugary mutant.

Rice (Oryza sativa L.) is one of the most important staple foods that feed more than 50% of the world’s population. With the improving of people’s living standard, eating quality of rice become the most important aims in current breeding programs. Amylose content (AC) and gelatinization temperature (GT) are the two main measures to estimate the rice grain quality. In rice, a total of 27 genes directly involved the rice starch biosynthesis effecting on the rice eating quality. It clearly identified chromosome 6 to be rich in the genes related to AC and GT properties (GBSS I, SSIIa and SBE I) along with other genomic regions scattered in rice genome. Rice blast, caused by the fungal pathogen M. oryzae, is the most devastating disease of rice and severely affects crop stability and sustainability worldwide. Many fungal genes involved in pathogenicity and rice genes involved in effector recognition and defense responses have been identified over the past decade. A total of 99 and 22 blast resistance genes have been identified and cloned; in which 45% were found in japonica cultivars, 51% in indica cultivars, and the rest 4% in wild rice species. Among them, three major resistance gene clusters have been characeterized: the Pik locus on Chromosome 11, and the Pita locus on Chromosome 12, the Piz locus on Chromosome 6 closely to the starch synthesis-related genes. These results could be important clues for studying the relationship between resistance / susceptible materials and eating quality.

One of the biotic stresses in rice production is rice blast disease caused by Magnaporthe oryzae, which is one of the most destructive fungal diseases in rice. We outlined an approach towards genome wide association study for the blast disease resistance in rice. In total, 295 rice accessions including 137 Heuristic Set accessions (HS) and 158 Korean Bred varieties (KB) were screened for the rice blast disease resistance. Firstly, Magnaporthe oryzae were inoculated to the rice seedlings of two weeks after germinations. Then, evaluation of the disease symptoms and checking the crossing point (CP) value were conducted one week after inoculation. To quantify the CP value, real-time polymerase chain reaction (PCR) was employed in combination with the primer pair and Taqman probe specific to Magnaporthe oryzae HYDROPHOBIN class 1 (MHP1) which is an indispensable unigene encoding HYDROPHOBIN for normal virulence expression. Based on these CP values from the PCR reactions containing a series of increasing concentration of cloned amplicon or fungal genomic DNA, correlation among the template’s copy number or its amount and amplification pattern was calculated. Reliability of this equation was further confirmed using the DNA samples from the rice leaves infected with compatible or incompatible strains of M. oryzae. These steps are still being undertaken, and after the complete process of disease resistance phenotyping for the whole population containing 295 accessions, GWAS will be performed to examine the associated genes involving in blast resistance mechanism using the whole genome resequencing data of 295 accessions. This approach would be a useful technique for identifying genetic loci responsible for natural variation in rice blast disease resistance and ultimately, new R genes which can improve the blast resistance in rice.

Plant specific gene family, NAC (NAM, ATAF, and CUC) transcription factors have been characterized for their roles in plant growth, development, and stress tolerance. In this study, we isolated OsNAC58 gene from rice and analysed expression level by inoculation of bacterial leaf blight pathogen, Xanthomonas oryzae pv. oryzae (Xoo). NAC transcription factor family can be divided into five groups (I–V). On the basis of phylogenetic analysis, OsNAC58 was fall into group III. 35S::OsNAC58-GFP fusion protein was localized on the nuclei. To investigate its biological function in the rice, we constructed vector for overexpression in rice, and then generated transgenic rices. Gene expression of OsNAC58-overexpressed transgenic rice lines were analyzed by northern blot. Analysis of disease resistance to pathogen Xoo, twelve OsNAC58-overexpressed transgenic rice lines showing high expression level of OsNAC58 were shown more resistant than wild type. These results suggest that OsNAC58 gene may play regulatory role during pathogen infection.

Disease is one of the devastating obstacles in the stable crop production. Numerous agronomical and chemical controls have been developed to overcome this problem, but the former is not sufficient for the maintaining the disease under the economic threshold level and the latter is not free from the environmental regulation. One of the most ideal solutions is resistance breeding. Resistance breeding has been majorly dependent on the resistance (R) genes conferring race-specific vertical resistance effective for limited populations within the pathogen species harboring avirulence (Avr) genes encoding effectors exactly matching with R gene products. In spite of its outstanding efficiency, improper management of above cultivars frequently resulted in the resistance break down due to the appearance and domination of the new races in the field. During the last two decades, mechanisms of disease resistance have been characterized and analyzed in the respect of genetics, biochemistry, molecular biology, cell biology, and evolution. Especially, a growing body of investigations has been focused on the resistance effective for multiple races or even more species of pathogen’s infections and also durable and long-lasting. In this manuscript, we will introduce the investigations searching for durable and broad-spectrum resistance and the considerations for their applications in the crop production will be presented.

Brown leaf spot, caused by necrotrophic Cochliobolus miyabeanus (imperfect; Bipolaris oryzae), is one of the devastating disease in rice (Oryza sativa). Especially, recommended agricultural system such as diminishing fertilizer and environmental alteration like temperature increment result in the favorable conditions for the outbreak of this disease. Lack of water supply also requires drought-tolerant rice cultivar. We hypothesized that regulation of programmed cell death (PCD) should be a common solution conferring resistance and tolerance against above biotic and abiotic stresses at the same time. Among 17 CYCLIC NUCLEOTIDE-GATED ION CHANNEL in rice (OsCNGCs), over expression of a CNGC resulted in lesion mimic phenotypes in Dongjin background. Further, knock out of a CNGC resulted in enhanced resistance against rice brown spot in the field. These results indicate that selected OsCNGC should be involved in the PCD regulation and fungal infection-specific regulation of OsCNGC expression might induce resistance against rice brown spot because of pathogen’s necrotrophic nature. Vitamin E, tocopherol, is involved in the accumulation inhibition of reactive oxygen species involving superoxide and hydrogen peroxide. Tocopherol cyclase in Nicotiana benthamiana (NtTC), which is included in tocopherol systhesis, conferred tolerance against drought stress to rice. We already have settled down the recombination system effectively removing selection markers in vector. Based on these systems, we will define fungal secretome and genome, confirmation of PAMPs/effectors, identification of rice pattern recognition receptor, and functional characterization of these rice genes in the respect of PCD and disease resistance. We will also develop marker-free transgenic rice tolerant to drought and/or salinity stresses. These works should give us a bundle of rice genes conferring resistance and tolerance against biotic and abiotic stresses and amount of information useful for the analyses of common cross talk points between disease resistance and stress-tolerance.

Plant specific gene family, NAC (NAM, ATAF, and CUC) transcription factors have been characterized for their roles in plant growth, development, and stress tolerance. In this study, we isolated OsNAC69 gene and analysed expression level by inoculation of bacterial leaf blight pathogen, Xanthomonas oryzae pv. oryzae (Xoo). NAC transcription factor family can be divided into five groups (I–V). On the basis of phylogenetic analysis, OsNAC69 was fall into group II. OsNAC69 was strongly induced 1 hr after infected with Xoo. To investigate its biological function in the rice, we constructed vector for overexpression in rice, and then generated transgenic rices. Gene expression of OsNAC69-overexpressed transgenic rice lines were analyzed by northern blot. Analysis of disease resistance to pathogen Xoo, nine OsNAC69-overexpressed transgenic rice lines showing high expression level of OsNAC69 were shown more resistant than wild type. These results suggest that OsNAC69 gene may play regulatory role during pathogen infection.