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Apios americana Medik, commonly known as American groundnut, is a leguminous perennial vine crop native to North America and is cultivated in Japan and Korea (Chu et al. 2019). Its tubers are edible and believed to be very nutritious, especially for women just after childbirth. The tubers also contain secondary metabolites, saponin and genistein, which is good for human health (Ichige et al. 2013). However, the storage of tubers at inappropriate temperatures and humidity levels can cause severe fungal infection, and adversely affect tuber quality. During March and April 2020, a white to pale-orange fungal mycelia were observed on stored American groundnut tubers, with 10 to 15% of seed tubers rotten. Infected tubers were collected, and fungal isolates were isolated on potato dextrose agar (PDA) using the single spore isolation method (Leslie and Summerell 2006). A pure culture (isolate JC20003) was obtained and stored at the Bioenergy Crop Research Institute, NICS, Muan, Republic of Korea. The fungus was cultured on PDA and V8 liquid media for 7 days at 25℃ to observe its morphological characteristics. The length and width of macroconidia ranged from 20.6 to 52.9 μm and 2.9 to 5.1 μm, respectively (n = 30). The microconidia were 8.5 to 14.9 μm and 2.3 to 4.2 μm in length and width, respectively (n = 30). Macroconidia were broadly falcate, strongly septate, 2 to 6 septations with dorsiventral curvature; chlamydospores were formed in chains; and microconidia were fusiform with 0 to 1 septation observed. Genomic DNA of the isolate was extracted using Solgent DNA extraction kit (Solgent, Daejeon, Korea), followed by PCR analysis using the internal transcribed spacer (ITS5/ITS4) and elongation factor (EF-1/EF2) genes (White et al. 1990; O'Donnel 2000). PCR products were sequenced and analyzed to confirm species identity (Yang et al. 2018). These sequences were deposited in GenBank (accession numbers MT703859/ITS and MT731939/EF). BLASTn search analysis showed 100% sequence similarity with Fusarium acuminatum (isolates N-51-1/ITS and WXWH24/EF). Based on morphological and molecular data analysis, the fungus was identified as F. acuminatum (Leslie and Summerell 2006; Marin et al. 2012). Pathogenicity tests were conducted on five tubers inoculated with 5 mm mycelial plugs with three replicates, while a non-mycelial plug served as the control. After 5 days of incubation in plastic containers at 25 °C with high humidity, typical symptoms developed. No symptoms were observed on the control tubers; F. acuminatum was re-isolated from artificially inoculated tubers to complete Koch's postulates. This is the first report on post-harvest tuber rot caused by F. acuminatum in Apios americana.

In July 2007, a leaf spot was observed on seedlings of tomato (Solanum lycopersicum) in a commercial greenhouse in Sungju County, Korea. Symptoms were dark, circular-to-irregular, water-soaked spots surrounded by chlorotic halos. Affected leaves turned yellow and readily detached. Two bacterial isolates, BC2642 and BC2923, were obtained from leaf lesions. The isolates were gram-negative, aerobic rods with a single flagellum. On peptone sucrose agar, colonies were yellow and raised with smooth margins. Starch and pectate hydrolysis tests were positive. Pathogenicity was confirmed by spraying cell suspensions containing 108 CFU/ml on seedlings of tomato (cv. Seokwang) and hot pepper (Capsicum annuum cv. Daekwang) in a greenhouse maintained at 28 ± 2°C. The isolates induced similar symptoms as those originally observed on tomato and also caused spots and a marginal blight of leaves of pepper 2 weeks after inoculation. No symptoms were noted on the control plants sprayed with sterilized distilled water. The identity of bacteria reisolated from spots on leaves of both plants were confirmed by comparison of patterns of metabolite fingerprints with those from preliminary identification of the isolates using the Biolog Microbial Identification System, version 4.2 (Biolog Inc., Hayward, CA), and reinoculation of the seedlings as above. The 16S rRNA gene (rrs) and the intergenic spacer (IGS) located between the rrs and the 23S rRNA gene, and partial sequences of gyrB were sequenced to aid in the identification of the isolates (1–3). A 2,134-bp fragment of the rrs and IGS regions and 701-bp fragment of the gyrB region from isolates BC2642 and BC2923 were compared with sequences in GenBank. Sequences from both isolates shared 100% similarity to sequences of Xanthomonas perforans (Genbank Accession No. AF123091). On the basis of the sequences and other assays, the two isolates were identified as X. perforans. To our knowledge, this is the first report of bacterial spot of tomato caused by X. perforans in Korea. Nucleotide sequence data reported are available under Accession Nos. GQ461739 and GQ461740 for rrs and IGS of BC2642 and BC2923, respectively, and GQ368187 and GQ380567 for gyrB of BC2642 and BC2923, respectively. An outbreak of this disease in the greenhouse may be due to the use of tomato seeds harvested in foreign countries where spot is known to occur. The disease is expected to have a significant economic impact on tomato culture in Korea. References: (1) J. B. Jones et al. Int. J. Syst. Evol. Microbiol. 50:1211, 2000. (2) N. Parkinson et al. Int. J. Syst. Evol. Microbiol. 59:264, 2009. (3) J. M. Young et al. Syst. Appl. Microbiol. 31:366, 2008.

In 2008 and 2009, a leaf spot of iceberg lettuce (Lactuca sativa var. capitata) was observed in two fields of Pyeongchang District and Jecheon City in South Korea, respectively. Disease incidence averaged 3.5% in the two fields. Symptoms on leaves included black, water-soaked, angular lesions with halos. Two bacterial isolates, BC2932 and BC3095, were recovered on trypticase soy agar (TSA) from lesions surface sterilized in 70% ethyl alcohol for 1 min. Both isolates had gram-negative, aerobic rods each with a single flagellum. Colonies on peptone sucrose agar were yellow and raised with smooth margins. Pathogenicity was evaluated on 3-week-old lettuce plants (cv. Avi). Bacteria were grown on TSA for 48 h at 28°C. A bacterial suspension in sterile distilled water (100 ml at 1 × 105 CFU/ml) was sprayed onto three plants for each isolate. Plants were maintained in a growth chamber at 28°C and 90% relative humidity. Isolates induced identical symptoms 3 days after inoculation as those originally observed in the fields. Pathogenicity of bacteria reisolated 10 days after inoculation from lesions surface sterilized in 70% ethyl alcohol was confirmed by inoculation as described above. No symptoms were observed on two control plants treated with sterile distilled water. Identity of bacteria reisolated from inoculated leaves was confirmed by PCR with specific primer set B162 (1). DNA of the original two isolates and 12 reisolates (two per inoculated plant) was amplified by PCR assay using Xanthomonas campestris pv. vitians Type B LMG938 (= BC2575) as a positive control treatment and X. axonopodis pv. vitians strain CFBP2538 (= BC2610) as a negative control treatment. The PCR amplicon for each of the 14 test isolates was identical in size to that of X. campestris pv. vitians Type B LMG938. No fragment of X. axonopodis pv. vitians CFBP2538 was amplified. Patterns of metabolic fingerprinting of the original two isolates were more similar to those of X. campestris pv. vitians Type B LMG938 than X. axonopodis pv. vitians CFBP2538 using Biolog Microbial Identification System Version 4.2 (Biolog Inc., Hayward, CA). X. campestris pv. vitians Type B LMG938, BC2932, and BC3095 were identified as X. campestris pv. pelargonii with a Biolog similarity index of 0.68, 0.45, and 0.78, respectively. Strain X. axonopodis pv. vitians CFBP2538 was identified as X. campestris pv. juglandis with an index of 0.48. The dnaK (958 bp), gyrB (859 bp), and rpoD (884 bp) regions were partially sequenced to aid in identification of the two original field isolates as well as X. campestris pv. vitians Type B LMG 938 and X. axonopodis pv. vitians CFBP2538 using reported PCR primers (3). Sequences were compared with those of reference strains of Xanthomonas in GenBank. Sequences of the three genes from the two lettuce field isolates shared 100% similarity to those of the genes of X. campestris pv. vitians Type B LMG938 and had a distance index value of 0.040, 0.099, and 0.046, respectively, with the reference strain of X. axonopodis pv. vitians CFBP2538 determined by p-distance modeling using MEGA Version 4.1 (2). Based on the pathogenicity test and sequence analyses, the isolates were identified as X. campestris pv. vitians Type B. To our knowledge, this is the first report of bacterial leaf spot of iceberg lettuce caused by X. campestris pv. vitians Type B in South Korea. References: (1) J. D. Barak et al. Plant Dis. 85:169, 2001. (2) K. Tamura et al. Mol. Biol. Evol. 24:1596, 2007. (3) J. M. Young et al. Syst. Appl. Microbiol. 31:366, 2008.

Sorghum (Sorghum bicolor (L.) Moench) is one of the top five cereal crops in the world, but the cultivation area in Korea is estimated to be about 3,000 ha (MIFFAF, 2012). In August 2014, anthracnose symptoms on sorghum leaves were observed in two fields in Yecheon (36.62°, 128.41°) and Youngwol (37.20°, 128.49°), South Korea. Symptoms on leaves were brownish red irregular lesions with yellow and tan borders. Some darkened conidiomata and setae were observed on the lesions of infected leaves. Approximately 20% of sorghum plants (cv. Hwanggeumchal) were affected in each field with an area of about 0.1 ha. Fragments of diseased infected leaves were surface sterilized with 1% NaOCl for 30sec. The pieces were placed on water agar and incubated at 25°C for 7days. Two isolates were obtained through single sporing and cultured on synthetic nutrient poor agar at 25°C for 14days. Conidia (n=30) of YN1458 isolate were falcate and measured 22.0 to 32.7 × 4.2 to 6.4 µm. Brown to black setae (n=20) had 1-3 septa, with tapering acute apices and 53.7 to 95.2 × 4.7 to 7.8 µm in size. Appressoria (n=30) were dark brown, usually irregular and 10.5 to 16.9 × 8.6 to 13.6 µm in size. Colonies on PDA produced salmon spore masses in the center of the colony, and whitish grey to dark color in reverse. The morphological characteristics of two isolates were similar. Based on morphology, two isolates were tentatively identified as Colletotrichum graminicola species complex (Cannon et al. 2012; Crouch and Tomaso-Peterson 2012). To clarify taxonomic placement, DNA extracted from mycelia of the two isolates was PCR amplified and sequenced targeting internal transcribed spacer (ITS) regions of rDNA, actin (ACT), chitin synthase 1(CHS-1), and beta-tubulin (TUB) genes (Weir et al. 2012). The sequences of the above four loci of YN1458 and YN1728 were deposited in GenBank with accession numbers KT351801, KT351802 (ITS); KY769869, KY69870 (ACT); KY769871, KY769872 (CHS-1); and KY769873, KY769874 (TUB), respectively. The sequencing results of two isolates showed 99.6% (ITS), 99.6% (ACT of YN1458), 100% (ACT of YN1728), 100% (CHS-1), 100% (TUB of YN1458) and 99.8% (TUB of YN1728) similarity with C. sublineola CBS 131301 (JQ005771, JQ005834, JQ005792, and JQ005855) by BLASTn. Based on the morphological characteristics and multigene sequence analysis, the two isolates were identified as C. sublineola. Pathogenicity of two isolates was confirmed by spraying conidial suspensions (106 conidia/mL) on leaves of 3-week-old sorghum seedlings (cv. Hwanggeumchal) using a pot assay (5 plants per isolate). The same number of seedlings were sprayed with sterile distilled water and served as controls. All plants were maintained in a greenhouse at 25/32°C with natural light. After one week, symptoms similar to those in the field were observed on the leaves inoculated with the pathogen, but not on the control leaves. Colletotrichum sublineola was consistently re-isolated from the inoculated leaves showing anthracnose symptoms and the pathogen identity was confirmed by observing morphological characteristics. So far, C. graminicola was known as the only causal agent pathogen of sorghum anthracnose in South Korea (KSPP, 2009). To our knowledge, this is the first report of C. sublineola causing anthracnose on sorghum in South Korea. Although sorghum is a small-scale crop in South Korea, it is necessary to study the biological and pathogenic characteristics of C. sublineola for effective control of sorghum anthracnose.

Maize yellow mosaic virus (MaYMV) is a novel putative polerovirus recently found in maize (Zea mays) in China and has been detected not only in Asia but also in Africa and South America (Chen et al. 2016; Goncalves et al. 2017; Palanga et al. 2017). In addition, MaYMV infection has also been reported in sugarcane (Saccharum spp.) and itch grass (Rottboellia cochinchinensis) (Yahaya et al. 2017). Recently, the first occurrence of MaYMV in South Korea has been reported from Panicum miliaceum and Sorghum bicolor using high-throughput RNA sequencing (Lim et al. 2018). Therefore, to confirm whether MaYMV exists in maize in South Korea, a total of 26 maize samples with yellowing, yellow stripe, and chlorosis symptoms were collected from three provinces (Chungcheongbuk-do, Gangwon-do, and Gyeongsangnam-do) in August and September 2017. Total RNA was extracted from all samples using the easy-spin Total RNA Extraction Kit (iNtRON Biotechnology, Seongnam, Korea). Reverse transcription polymerase chain reaction (RT-PCR) was conducted using SuPrimeScript RT-PCR Premix (GeNet Bio, Daejeon, Korea) and MaYMV-specific primers (Chen et al. 2016), producing an amplicon with expected size of 753 bp, using protocols described previously (Lim et al. 2018). Five out of six samples collected from Chungcheongbuk-do, five out of 10 samples collected from Gangwon-do, and one out of 10 samples collected from Gyeongsangnam-do were confirmed to be infected with MaYMV. One RT-PCR fragment of MaYMV from each region (Gangwon-do, Chungcheongbuk-do, and Gyeongsangnam-do) was directly sequenced (Macrogen, Daejeon, Korea), and the sequences were deposited in GenBank under accession numbers MG020517, MG020518, and MG020519, respectively. The partial nucleotide sequences of MaYMV determined in each sample collected from Chungcheongbuk-do and Gyeongsangnam-do were identical, and these nucleotide sequences differed by one nucleotide from that identified in the sample collected from Gangwon-do. The NCBI BLAST search showed that the three MaYMV isolates shared high nucleotide sequence homology (99 to 100%) with isolates Yunnan3 (KU291099) and Yunnan4 (KU291100) from maize in China. The MaYMV-infected samples showed yellow stripe and chlorosis symptoms, which tend to first appear on the tip and edge of the leaves and become worse. However, further studies are needed, because it is uncertain whether the symptoms were caused by a single infection with MaYMV. To the best of our knowledge, this is the first report of MaYMV on Z. mays in South Korea.

Maize yellow mosaic virus (MaYMV) is a tentative new Polerovirus, which was recently identified from maize (Zea mays) in China (Chen et al. 2016). MaYMV has also been reported to infect sugarcane (Saccharum spp.) and itch grass (Rottboellia cochinchinensis), and it has been reported in Asia, Africa and South America (Goncalves et al. 2017; Palanga et al. 2017; Yahaya et al. 2017). In this study, MaYMV was detected in Panicum miliaceum and Sorghum bicolor using Illumina HiSeq2500 system by Theragen Etex Bio Institute (Suwon, Korea) and SG-VIPdb by SeqGenesis (Daejeon, Korea), as described by Lim et al. (2015). Twenty samples of P. miliaceum and sixty three samples of S. bicolor were collected from July to September and from June to October, 2016, respectively, in South Korea. The high-throughput RNA sequencing of the samples mixed into one pool resulted in a single large contig (5606-nt) with nearly complete MaYMV genome coverage. The contig was assembled from a total of 234,537 reads; the maximum, minimum...

The king oyster mushroom, Pleurotus eryngii, has become a popular crop because of its unique flavor and texture and is cultivated in many areas in Korea. In 2003, symptoms of water-soaked lesions and soft rot in the stipes and pileus of cultivated P. eryngii was observed in Jinju, Korea. Diseased tissue was plated on nutrient media. Dominate colonies were yellow, convex, circular with smooth margins, and had a shiny texture. Computer analysis of the data gathered, using the API kit (50CHE, bioMérieux, Marcy-l'Etoile, France), showed that the strain belongs to the Enterobacteriaceae. Although the API system did not give an exact identification, the metabolic profile of the bacterial strain closely resembled the database profile of Pantoea sp. (positive for acid production from the fermentation of d-fructose, d-galactose, d-glucose, d-trehalose, and d-ribose and negative for oxidase, urease, pectate, and thiosulfate). The 16S rDNA sequence of the bacterium was determined (GenBank Accession No. AY530796). When compared with those in GenBank, the bacterium was determined to belong to the Enterobacteriaceae family of the Gammaproteobacteria, and the highest degree of sequence similarity was found to be with Pantoea ananatis strain BD 588 (97.4%) and Pantoea ananatis strain Pna 97-1 (97.3%). In the phylogenetic tree, the bacterium clearly related to the Pantoea lineage, as evidenced by the high bootstrap value. A BLAST search with 16S rDNA sequence of the bacterium supported the API results that the isolate belongs to a species of Pantoea. Pathogenicity tests of this new Pantoea isolate were carried out with bacterial suspensions (approximately 1 × 106 CFU/ml) that were grown for 24 h in Luria-Bertani broth cultures. These were used to inoculate directly on the mycelia of P. eryngii that had been cultivated for 35 days in a plastic bottle. The water and broth were also inoculated to another set of bottles as a control experiment. Inoculated bottles were incubated in a cultivation room at 16 to 17°C with relative humidity between 80 and 95%. Early symptoms of the disease included a dark brown water drop that developed on hypha and primordium of the mushrooms after 5 to 7 days. After 13 days, water-soaked lesions developed on the stipes and pileus, and the normal growth of the mushrooms was inhibited. An offensive odor then developed along with a severe soft rot that was similar to the disease symptoms observed under natural conditions. Mushrooms in control bottles did not develop symptoms. Koch's postulates were fulfilled by isolating bacteria from typical lesions from inoculated mushrooms that were identical to the inoculated strain in colony morphology and biochemical characteristics. Pantoea ananatis was first reported as a pathogen of pineapple fruit causing brown rot (3). Several bacterial diseases, such as brown blotch on cultivated mushrooms by Pseudomonas tolaasii (2) and bacterial soft rot on winter mushroom by Erwinia carotovora subsp. Carotovora, causing severe damage to mushrooms are known (1). However, no Pantoea sp. induced disease of edible mushroom has been previously reported. To our knowledge, this is the first report of soft rot disease on P. eryngii caused by Pantoea sp. References: (1) H. Okamoto et al. Ann. Phytopathol. Soc. Jpn. 65:460. 1999. (2) S. G. Paine. Ann. Appl. Biol. 5:206. 1919. (3) F. B. Serrano. Philipp. J. Sci. 36:271, 1928.