Search

Soybean (Glycine max L.) is one of the most important crop plants in the Republic of Korea. Here, we conducted a soybean virome study. We harvested a total of 172 soybean leaf samples showing disease symptoms from major soybean-growing regions in the Republic of Korea. Individual samples were examined for virus infection by RT-PCR. Moreover, we generated eight libraries representing eight provinces by pooling samples and four libraries from single samples. RNA-seq followed by bioinformatics analyses revealed 10 different RNA viruses infecting soybean. The proportion of viral reads in each transcriptome ranged from 0.2 to 31.7%. Coinfection of different viruses in soybean plants was very common. There was a single dominant virus in each province, and this geographical difference might be related to the soybean seeds that transmit viruses. In this study, 32 viral genome sequences were assembled and successfully used to analyze the phylogenetic relationships and quasispecies nature of the identified RNA viruses. Moreover, RT-PCR with newly developed primers confirmed infection of the identified viruses in each library. Taken together, our soybean virome study provides a comprehensive overview of viruses infecting soybean in eight geographical regions in the Republic of Korea and four single soybean plants in detail.

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.

Soybean mosaic virus (SMV) is a prevalent pathogen that causes significant yield reduction in soybean production worldwide. SMV belongs to potyvirus and causes typical symptoms such as mild mosaic, mosaic and necrosis. SMV is seed-borne and also transmitted by aphid. Eleven SMV strains, G1 to G7, G5H, G6H, G7H, and G7a were reported in soybean varieties in Korea. A reverse transcription loop-mediated isothermal amplification (RT-LAMP) method allowed one-step detection of gene amplification by simple procedure and needed only a simple incubator for isothermal template. This RT-LAMP method allowed direct detection of RNA from virus-infected plants without thermal cycling and gel electrophoresis. In this study, we designed RT-LAMP primers named SML-F3/B3/FIP/BIP from coat protein gene sequence of SMV. After the reaction of RT-LAMP, products were identified by electrophoresis and with the detective fluorescent dye, SYBR Green I under daylight and UV light. Optimal reaction condition was at 58°C for 60 min and the primers of RT-LAMP showed the specificity for nine SMV strains tested in this study.

Garlic generally becomes coinfected with several types of viruses belonging to the Potyvirus, Carlavirus, and Allexivirus genera. These viruses produce characteristically similar symptoms, they cannot be easily identified by electron microscopy (EM) or immunological detection methods, and they are currently widespread around the world, thereby affecting crop yields and crop quality adversely. For the early and reliable detection of garlic viruses, virus-specific sets of primers, including species-specific and genus-specific primers were designed. To effectively detect the twelve different types of garlic viruses, primer mixtures were tested and divided into two independent sets for multiplex polymerase chain reaction (PCR). The multiplex PCR assays were able to detect specific targets up to the similar dilution series with monoplex reverse transcription (RT)-PCR. Seventy-two field samples collected by the Gyeongbuk Agricultural Technology Administration were analyzed by multiplex RT-PCR. All seventy two samples were infected with at least one virus, and the coinfection rate was 78%. We conclude that the simultaneous detection system developed in this study can effectively detect and differentiate mixed viral infections in garlic.

A novel allele of the putative soybean raffinose synthase gene, RS2, was discovered in PI200508 that is associated with the low raffinose and stachyose content. Soybean line PI200508 was identified as expressing reduced levels of raffinose and stachyose as well as elevated levels of sucrose. The RS2 mutant gene shows three base pairs InDel with the normal gene. Based on InDel region we developed novel co-dominant and dominant marker. The aim of this study was to develop Korean soybean cultivars, Daewon, Cheongja, and Danmiput, containing low levels of raffinose and stachyose. A specific markers assay for the PI200508 RS2 allele was developed to allow direct selection of the low raffinose and stachyose phenotype. Our findings highlight the efficiency of allele-specific markers in selection, which is evident in the matching genotype and results of the HPLC in the F2 generations of Daewon×PI200508 population.

The changes of growth characteristics and antioxidant activity for selection of optimum germinated temperature on common bean ( Phaseolus vulgaris L.). Common beans (IT100888, IT102849, and IT231267) were cultivated at 20℃, 23℃ and 25℃ during 5 days of germination. The range of whole length, hypocotyls length, thickness, abnormal germination and yield rate of sprouts was 7.27~27.62 cm, 3.10~18.86 cm, 1.80~2.27 mm, 5.54~18.34% and 205.95~ 618.71%, respectively. Antioxidant activities of common beans with germination temperature investigated. Common beans (IT100888, IT102849, and IT231267) germinated at 20℃, 23℃ and 25℃ during 5 days, and then extracted with 80% ethanol, and analyzed for total polyphenol content, DPPH and ABTS radical scavenging activity. Total polyphenol content increased from 474 mg GA eq/100 g sample for IT231267 to 1364 mg GA eq/g sample for 23℃ of germination. DPPH radical scavenging activity of IT102849 increased from 189mg Trolox eq./100 g sample (20℃) to 1073mg Trolox eq./100 g sample (23℃) also ABTS radical scavenging activity of IT234267 increased from 479 mg Trolox eq./100 g sample (20℃) to 1134 mg AA eq/100 g (23℃). These results suggest that germination temperature for increasing antioxidant activities may be 23℃.

Bacterial diseases in soybean are bacterial pustule by Xanthomonas axonopodis pv. glycines, wildfire by Pseudomonas syringae pv. tabaci, bacterial blight by Pseudomonas savastanoi pv. glycines and bacterial brown spot by Pseudomonas syringae pv. syringae in Korea. It is difficult to identify each disease by early symptoms in fields, because the initial symptoms of these diseases are very similar to each other. In this study, we developed multiplex PCR detection method for rapid and accurate diagnosis of bacterial diseases. The glycinecin A of X. axonopodis pv. glycines, the tabtoxin of P. syringae pv. tabaci, the coronatine of P. savastanoi pv. glycines and the syringopeptin of P. syringae pv. syringae have been reported previously. These bacteriocin or phytotoxin producing genes were targeted to design the specific diagnostic primers. The primer pairs for diagnosis of each bacterial diseases were selected without nonspecific reactions. The studies on simultaneous diagnosis method were also conducted with primarily selected 21 primers. As a result, we selected PCR primer sets for multiplex PCR. Sizes of the amplified PCR products using the multiplex PCR primer set consist of 280, 355, 563 and 815 bp, respectively. This multiplex PCR method provides a efficient, sensitive and rapid tool for the diagnosis of the bacterial diseases in soybean.

Crop Protection Division, National Academy of Agricultural Science, Rural Development Administration, Suwon 441-707, Korea(Received on February 23, 2012; Revised on August 9, 2012; Accepted on August 10, 2012)In July, 2009, proso millet (Panicum miliaceum), which showing the bacterial brown stripes on leaf sheaths,was collected in Miryang in Korea. Symptoms were systemic brown necrotic stripe lesions on the leaf sheathsand stems, and these symptoms were found in the entire field. The causal agent isolated from symptomaticplants was identified as an Acidovorax avenae subsp. avenae, based on its biochemical and physiologicalcharacteristics and also confirmed by the Biolog data and 16S rRNA gene sequence analysis. Also it causedhypersensitive response (HR) when it was inoculated onto the tobacco and tomato. It caused similarsymptoms when inoculated onto proso millet. This is the first report of A. avenae subsp. avenae, the causalagent of bacterial brown stripe of the proso millet in Korea. Keywords : Acidovorax avenae, Bacterial stripe, Panicum miliaceum기장(Panicum miliaceum L.)은 아프리카, 아시아, 남미에서 널리 이용되는 식량작물로 이들 지역의 단백질 공급에 기여하고 있다(Park 등, 2009). 또한 비타민, 무기질및 식이섬유 등의 기능성 성분의 함량이 높고 다양한 생리활성 물질이 많이 함유되어 있어 건강을 유지시키는 보조식량으로서의 역할이 중요시되고 있다(Ko 등, 2011). Acidovorax avenae subsp. avenae는 1909년 미국 오하이오 지역에서 귀리의 잎마름을 일으키는 식물병원세균으로 Manns(1909)에 의해 처음 보고된 후 벼 세균성줄무늬병(Goto, 1964; Kadota, 1996; Shakya 등, 1985), 옥수수의 세균성 줄기부패병(Rosen, 1926; Summer와 Schaad,1977), 조의 갈색줄무늬병(Rosen, 1926), 사탕수수와 기장의 붉은줄무늬병(Martin과 Wismer, 1989)을 일으키는 것으로 보고되었다. 국내에서는 벼 세균성줄무늬병(Shakya,1980)과 옥수수 줄기썩음병(Lee, 1991)이 보고되어 있으나, 기장에서는 아직 보고된 바 없다.본 연구는 국내에서 기장에 새롭게 발생한 세균성줄무늬병의 병징 및 병원세균의 균학적 특성을 보고하고자 한다.

In 2005, a survey was conducted to identify virus diseases on victory onion, Allium victorialis var. platyphyllum grown in Ulleung island located in the East Sea. A total of 61 samples were collected from victory onion in the neighborhood of Seonginbong. The identification of viruses from the samples were carried out by electron microscopy and RT-PCR using primers species specific to GCLV, LYSV, SLV, OYDV and genus specific to Allexivirus, respectively. From sixty-one samples, filamentous rod particles (600-900 nm) were detected from four victory onion samples in EM, three samples containing SLV and one sample containing both SLV and Allexivirus in RT-PCR analysis, respectively. Victory onions naturally infected by the viruses were asymptomatic apparently. The viruses detected by RT-PCR were further characterized by the nucleotide sequence analysis of the coat protein region. Three isolates of SLV showed approximately 99% identities in the nucleotide and amino acid sequences, suggesting that they were likely to be the same strain. On the other hand, they showed approximately 75.7~83.7% identities in the nucleotide and 89.2~97.0% in amino acid sequences compared with the previously reported SLV isolates in Allium. The CP gene of the Allexivirus showed approximately 99.2% nucleotide identities and 98.8% amino acid identities with Garlic virus A. However, there was relatively low homology ranging from 60.6% to 81.5% compared with other Allexiviruses (GarV-C, GarV-E, GarV-X, GMbMV, and Shal-X). These data suggested that two viruses, SLV and GarV-A identified from victory onion, are named SLV-Ulleungdo and GarV-A-Ulleungdo, respectively. This is the first report of viruses infecting victory onion.

During the period from 1999 to 2008, we surveyed the major diseases incidence of rice in Korea. Leaf blast showed 0.85% of the diseased leaf area in 2000 and then consistently decreased to 0.02% by 2008. However, panicle blast irregularly appeared by the years depending on weather conditions for disease development from heading to milk stage of rice. Diseased lesion height of sheath blight had the lowest (10.1%) incidence in 2001 and the highest (21.4%) incidence in 2007. A negative corelation ($r

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...

This study was conducted to decide disease incidence level of rice leaf blast required for reasonable fungicide application in paddy field. We induced the disease development by inoculating rice blast pathogens on rice seedlings (Jinmibyeo) in the greenhouse and transplanting the infected seedlings in the field two weeks after rice plants were transplanted. We scored the disease incidence, grouped and marked according to degree of percentage of diseased leaf area at maximum stage of disease development. The percent diseased leaf area (PDLA) had negative correlations with panicle number per hill, ripened grain (%), and total yield; their correlation coefficients (r), , and , respectively. However, it had positive correlations with spikelets per panicle and thousand grain weight; their correlation coefficients (r), and , respectively. Gain threshold (GT) calculated based on control cost and market price was estimated to be 8.35. Economic injury level (EIL) obtained based on GT and coefficient of damage of regression equation between disease incidence and the different yield components; panicle number per hill, spikelets per panical, ripened grain(%), thousand grain weight and yield were 41.8, 9.7, 19.1, 291.1 and 3.4%, respectively. Economic threshold (ET) for yield was 2.7% () on PDLA. These results suggest that application of fungicide is necessary when two under leaves are almost covered with lesions or contained more than twenty large lesions under leaves at maximum tillering stage.

In year 2003, a soybean(Glycine max) sample showing severe dwarfing symptom was collected from a farmers` field in Cheongsong in Korea. The results from the diagnosis of the sample by RT-PCR revealed that it was infected by Soybean dwarf virus(SbDV), SbDV-L81. This study could be the first report of the occurrence of the virus in Korea. To further characterize the virus, the partial nucleotide sequence of the genomic RNA of SbDV-L81 was determined by RT-PCR using species-specific primers. The sequences were analyzed and subsequently compared to previously characterized strains of SbDV based on the pattern of symptom expression and vector specificities. The intergenic region between ORF 2 and 3 and the coding regions of ORF 2, 3 and 4 were relatively similar to those of dwarfing strains(SbDV-DS and DP) rather than those of yellowing strains(SbDV-YS and YP). Likewise, the result from the analysis of 5`-half of the coding region of ORF5 indicated that SbDV-L81 was closely related to strains(SbDV-YP and DP) transmitted by Acyrthosiphon pisum. These data from the natural symptom and the comparisons of five regions of nucleotide sequences of SbDV suggested that SbDV-L81 might be closely related SbDV-DP.

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.