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Host shifting and host expansion of fungal plant pathogens increases the rate of emergence of new pathogens and the incidence of disease in various crops, which threaten global food security. Magnaporthe species cause serious disease in rice, namely rice blast disease, as well as in many alternative hosts, including wheat, barley, and millet. A severe outbreak of wheat blast due to Magnaporthe oryzae occurred recently in Bangladesh, after the fungus was introduced from South America, causing great loss of yield. This outbreak of wheat blast is of growing concern, because it might spread to adjacent wheat-producing areas. Therefore, it is important to understand the host range and population structure of M. oryzae and related species for determining the evolutionary relationships among Magnaporthe species and for managing blast disease in the field. Here, we collected isolates of M. oryzae and related species from various Poaceae species, including crops and weeds surrounding rice fields, in Korea and determined their phylogenetic relationships and host species specificity. Internal transcribed spacer-mediated phylogenetic analysis revealed that M. oryzae and related species are classified into four groups primarily including isolates from rice, crabgrass, millet and tall fescue. Based on pathogenicity assays, M. oryzae and related species can infect different Poaceae hosts and move among hosts, suggesting the potential for host shifting and host ex- pansion in nature. These results provide important information on the diversification of M. oryzae and re- lated species with a broad range of Poaceae as hosts in crop fields.

During an investigation of fungi of the order Mucorales from freshwater and sediment samples in Korea, we isolated six strains, NNIBRFG6649, NNIBRFG6255, NNIBRFG1498, CNUFC-YJ13, CNUFC-YR7, and NNIBRFG2739. The morphology and phylogeny of these strains were analyzed. Based on the morphological characteristics and molecular data from internal transcribed spacer (ITS) region, the isolates NNIBRFG6649 and NNIBRFG6255 were identified as Mucor abundans, and M. aligarensis, respectively. The isolates NNIBRFG1498 and CNUFC-YJ13 were identified as M. moelleri, whereas the isolates CNUFC-YR7 and NNIBRFG2739 were identified as M. heterogamus. To the best of our knowledge, M. abundans, M. aligarensis, M. moelleri, and M. heterogamus have not yet been reported in Korea.

We investigated the diversity of aquatic fungi from freshwater environments in Korea. From the survey of aquatic fungi, three Tetracladium (Leotiomycetes, Helotiales) strains, NNIBRFG814, NNIBRFG1997, and NNIBRFG3891, were isolated from decaying leaves of Fraxinus rhynchophylla located in Taebaek-si, Gangwon-do; freshwater foam in the freshwater of the Gam stream in Gimcheon-si; and from filtered freshwater of the Yangsan stream in Mungyeong-si, Gyeongsangbuk-do, respectively. The isolated fungal strains were identified using ITS sequence analysis and morphological characters. A sequence analysis indicated that the fungal isolates were closely related to Tetracladium breve MK371730 (100%, NNIBRFG814), Tetracladium setigerum KU519120 (98.96%, NNIBRFG1997), and T. marchalianum MK353126 (98.14%, NNIBRFG3891). In terms of growth conditions, it was confirmed that NNIBRFG814 grew best at 20 °C, did not grow above 30 °C, and grew at 5 °C as a psychrophilic fungus. NNIBRFG814 was included in the T. breve clade but its morphology was not similar to that of T. breve. Thus, NNIBRFG814 is a new species, and T. fraxineum sp. nov. NNIBRFG1997 and NNIBRFG3891 are the first records in Korea of T. setigerum and T. marchalianum, respectively.

Host shifting and host expansion of fungal plant pathogens increases the rate of emergence of new pathogens and the incidence of disease in various crops, which threaten global food security. Magnaporthe species cause serious disease in rice, namely rice blast disease, as well as in many alternative hosts, including wheat, barley, and millet. A severe outbreak of wheat blast due to Magnaporthe oryzae occurred recently in Bangladesh, after the fungus was introduced from South America, causing great loss of yield. This outbreak of wheat blast is of growing concern, because it might spread to adjacent wheat-producing areas. Therefore, it is important to understand the host range and population structure of M. oryzae and related species for determining the evolutionary relationships among Magnaporthe species and for managing blast disease in the field. Here, we collected isolates of M. oryzae and related species from various Poaceae species, including crops and weeds surrounding rice fields, in Korea and determined their phylogenetic relationships and host species specificity. Internal transcribed spacer-mediated phylogenetic analysis revealed that M. oryzae and related species are classified into four groups primarily including isolates from rice, crabgrass, millet and tall fescue. Based on pathogenicity assays, M. oryzae and related species can infect different Poaceae hosts and move among hosts, suggesting the potential for host shifting and host expansion in nature. These results provide important information on the diversification of M. oryzae and related species with a broad range of Poaceae as hosts in crop fields.

Margaritispora aquatica is an aquatic fungal species found in leaf litter. Here, we report the 42.5-Mb draft genome sequence of M. aquatica strain NNIBRFG339, which comprises 61 scaffolds and has an overall G+C content of 45.77% and an N50 value of 1.856 Mb.

During an investigation of fungi of the order Mucorales from freshwater and sediment samples in Korea, we isolated six strains, NNIBRFG6649, NNIBRFG6255, NNIBRFG1498, CNUFC-YJ13, CNUFC-YR7, and NNIBRFG2739. The morphology and phylogeny of these strains were analyzed. Based on the morphological characteristics and molecular data from internal transcribed spacer (ITS) region, the isolates NNIBRFG6649 and NNIBRFG6255 were identified as Mucor abundans, and M. aligarensis, respectively. The isolates NNIBRFG1498 and CNUFC-YJ13 were identified as M. moelleri, whereas the isolates CNUFC-YR7 and NNIBRFG2739 were identified as M. heterogamus. To the best of our knowledge, M. abundans, M. aligarensis, M. moelleri, and M. heterogamus have not yet been reported in Korea.

Aquanectria penicillioides is a common aquatic fungal species. Here, we report the 53.7-Mb draft genome sequence of A. penicillioides strain NNIBRFG19, which has an overall G+C content of 47.93%, comprising 13 scaffolds with an N50 value of 4.932 Mb.

Hymenoscyphus tetracladius (anamorph, Articulospora tetracladia) is a common aquatic hyphomycetous fungus. Here, we report the draft genome sequence of H. tetracladius strain NNIBRFG329, which comprises 41.8 Mb in 20 scaffolds with an overall G+C content of 46.95% and an N50 value of 3.973 Mb.

A sequential planting method was developed to screen rice plants with durable resistance against rice blast in a short time, and applied for several years in Korean rice breeding program. In this study, we showed the advantages of a sequential planting method compared to other pathogenicity tests. The correlation analysis among three pathogenicity tests and other factors demonstrated that durable resistance depended on the average of diseased leaf area and the number of compatible pathogens. Significant correlations were found in the nursery test but not in the field test result. In addition, we traced changes in the pathogen population during sequential planting stages through re-isolation of the pathogen. The portion of compatible pathogens was increased during sequential planting. Through this study, we provide an effective sequential planting method and direction of durable resistance in a breeding program.

For application of sodium hypochlorite as a seed disinfectant to the control of bakanae disease caused by Gibberella fujikuroi in rice, we investigated the effects of sodium hypochlorite for antifungal activity, eliminating fungus from seeds and reducing disease occurrence in vitro and greenhouse. The viability of the pathogen was significantly reduced at 80 ml/l concentration of sodium hypochlorite, and the pathogens did not grow at over 100 ml/l concentration of sodium hypochlorite. The effect of eliminating fungus was 90% at treatment of 0.3% sodium hypochlorite solution to infected rice seeds for eight hours. When the rice seeds were soaked into 0.5% and 0.3% sodium hypochlorite solutions for twelve hours, the disease incidences of rice seedling were remarkably reduced to 4.3% and 4.7%, respectively, compared to 97.3% of non-treatment control. The rates of seedling stand were 29.1% and 26.9% higher with the sodium hypochlorite treatment than that of non-treatment control. When prochloraz and sodium hypochlorite was treated to naturally severely infested rice seeds with bakanae disease, the disinfection effect was higher than that of prochloraz alone treatment. When the seeds were soaked in sodium hypochlorite before or after prochloraz, the rate of seed contamination was low as 4.0% or 6.3%, respectively, compared to prochloraz alone as 13.7%. The disease incidence was low as 3.7% or 8.3%, respectively, compared to prochloraz alone as 14.3%. The disinfection effect of treatment with prochloraz after sodium hypochlorite was higher than that of treatment with prochloraz before sodium hypochlorite.

Rice Breeding and Cultivation Research Division, National Institute of Crop Science, Rural Development Administration, Iksan 570-080, Korea(Received on September 3, 2013; Revised on November 22, 2013; Accepted on November 28, 2013)Rice blast is one of the most serious disease threatening stable production of rice. Breeding of resistantcultivars has been used as the most effective and useful method to controll rice blast caused by Magnaportheoryzae. To collect rice blast isolates in fields and test their pathogenicity on new cultivars are important forestablishment of new resistant cultivars breeding program of rice. Pathotypes of Korean rice blast isolateshave been categorized to Korean differential race system developed in 1985. However, it is little known aboutgenetic background of Korean differential cultivars, so that it is hard to understand for relationship betweeneach pathogen and each host plant at genetic level. In this study, we suggested necessity of a new differentialsystem by analyzing pathogenic responses between 24 monogenic rice lines and 200 Korean rice blast isolates.In addition, we determined the nine representative resistant genes based on the resistance responses of themonogenic lines to rice blast isolates, indexed resistant responses of the monogenic lines to ten representativerice blast isolates and selected 30 Korean representative rice blast isolates proper to Korean system. We thinkthe newly developed differential race system can be broadly used to select resistant cultivars to rice blast inKorea.Keywords : Differential system, Magnaporthe oryzae, Monogenic lines, Resistance, Rice blast

Rice blast, caused by the pathogen Magnaporthe oryzae, is a serious hindrance to rice production and has emerged as an important model for the characterization of molecular mechanisms relevant to pathogenic development in plants. Similar to other pathogenic fungi, conidiation plays a central role in initiation of M. oryzae infection and spread over a large area. However, relatively little is known regarding the molecular mechanisms that underlie conidiation in M. oryzae. To better characterize these mechanisms, we identified a conidiation-defective mutant, ATMT0225B6 (MoCDC15T-DNA), in which a T-DNA insertion disrupted a gene that encodes a homolog of fission yeast cdc15, and generated a second strain containing a disruption in the same allele (ΔMoCDC15T-DNA). The cdc15 gene has been shown to act as a coordinator of the cell cycle in yeast. Functional analysis of the MoCDC15T-DNA and ΔMoCDC15T-DNA mutants revealed that MoCDC15 is required for conidiation, preinfection development and pathogenicity in M. oryzae. Conidia from these mutants were viable, but failed to adhere to hydrophobic surface, a crucial step required for subsequent pathogenic development. All phenotypic defects observed in mutants were rescued in a strain complemented with wild type MoCDC15. Together, these data indicate that MoCDC15 functions as a coordinator of several biological processes important for pathogenic development in M. oryzae.

Agrobacterium tumefaciens-mediated transformation (ATMT) has become a prevalent tool for functional genomics of fungi, but our understanding of T-DNA integration into the fungal genome remains limited relative to that in plants. Using a model plant-pathogenic fungus, Magnaporthe oryzae, here we report the most comprehensive analysis of T-DNA integration events in fungi and the development of an informatics infrastructure, termed a T-DNA analysis platform (TAP). We identified a total of 1110 T-DNA-tagged locations (TTLs) and processed the resulting data via TAP. Analysis of the TTLs showed that T-DNA integration was biased among chromosomes and preferred the promoter region of genes. In addition, irregular patterns of T-DNA integration, such as chromosomal rearrangement and readthrough of plasmid vectors, were also observed, showing that T-DNA integration patterns into the fungal genome are as diverse as those of their plant counterparts. However, overall the observed junction structures between T-DNA borders and flanking genomic DNA sequences revealed that T-DNA integration into the fungal genome was more canonical than those observed in plants. Our results support the potential of ATMT as a tool for functional genomics of fungi and show that the TAP is an effective informatics platform for handling data from large-scale insertional mutagenesis.

Rapid translation of genome sequences into meaningful biological information hinges on the integration of multiple experimental and informatics methods into a cohesive platform. Despite the explosion in the number of genome sequences available, such a platform does not exist for filamentous fungi. Here we present the development and application of a functional genomics and informatics platform for a model plant pathogenic fungus, Magnaporthe oryzae. In total, we produced 21,070 mutants through large-scale insertional mutagenesis using Agrobacterium tumefaciens-mediated transformation. We used a high-throughput phenotype screening pipeline to detect disruption of seven phenotypes encompassing the fungal life cycle and identified the mutated gene and the nature of mutation for each mutant. Comparative analysis of phenotypes and genotypes of the mutants uncovered 202 new pathogenicity loci. Our findings demonstrate the effectiveness of our platform and provide new insights on the molecular basis of fungal pathogenesis. Our approach promises comprehensive functional genomics in filamentous fungi and beyond.

Insertional mutagenesis of Magnaporthe oryzae led to the identification of MCK1, a pathogenicity gene predicted to encode mitogen-activated protein kinase kinase kinase (MAPKKK) homologous to BCK1 in Saccharomyces cerevisiae. Targeted disruption of MCK1 resulted in the fungus undergoing autolysis and showing hypersensitivity to cell-wall-degrading enzyme. The mck1 produced significantly reduced numbers of conidia and developed appressoria in a slightly retarded manner compared with the wild type. Appressorium of the mck1 mutant was unable to penetrate into plant tissues, thereby rendering the mutant nonpathogenic. Cytorrhysis assay and monitoring of lipid mobilization suggested that the appressorial wall was altered, presumably affecting the level of turgor pressure within appressorium. Furthermore, the mck1 mutant failed to grow inside plant tissue. Complementation of the mutated gene restored its ability to cause disease symptoms, demonstrating that MCK1 is required for fungal pathogenicity. Taken together, our results suggest that MCK1 is an MAPKKK involved in maintaining cell wall integrity of M. oryzae, and that remodeling of the cell wall in response to host environments is essential for fungal pathogenesis.