First report of beet western yellows virus in radish in Korea.

Radish (Raphanus sativus L.) is an important root vegetable widely consumed in kimchi in Korea. In October 2021, radish leaves with virus-like symptoms of mosaic and yellowing were collected in three fields around Naju, Korea (Fig. S1). A pooled sample (n = 24) was screened for causal viruses by high-throughput sequencing (HTS), with detection confirmed by reverse transcription (RT) PCR. Total RNA was extracted from symptomatic leaves using the Plant RNA Prep kit (Biocube System, Korea), and a cDNA library was constructed and sequenced on an Illumina NovaSeq 6000 system (Macrogen, Korea). De novo transcriptome assembly yielded 63,708 contigs, which were analyzed against the viral reference genome database in GenBank by BLASTn and BLASTx searches. Two large contigs were clearly of viral origin. BLASTn analysis showed that a 9,842-bp contig (4,481,600 mapped reads, mean read coverage 68,758.6×) had 99% identity (99% coverage) with isolate CCLB of turnip mosaic virus (TuMV) from radish in China (KR153038). A second contig of 5,711 bp (7,185 mapped reads, mean read coverage 189.9×) had 97% identity (99% coverage) with isolate SDJN16 of beet western yellows virus (BWYV) from Capsicum annuum in China (MK307779). To confirm the presence of these viruses, total RNA extracted from 24 leaf samples was subjected to RT-PCR using primers specific for TuMV (N60_5'-ACATTGAAAAGCGTAACCA-3' and C30_5'-TCCCATAAGCGAGAATACTAACGA-3', amplicon 356 bp) and BWYV (95F_5'-CGAATCTTGAACACAGCAGAG-3' and 784R_5'-TGTGGG ATCTTGAAGGATAGG-3', amplicon 690 bp) for virus detection. Of the 24 samples, 22 were positive for TuMV and 7 were co-infected with BWYV. Single infection of BWYV was not detected. Infection with TuMV, the predominant virus in radish in Korea, was previously reported (Choi and Choi, 1992; Chung et al., 2015). To determine the complete genomic sequence of the BWYV isolate (BWYV-NJ22) from radish, RT-PCR was conducted using eight overlapping primer pairs designed according to the alignment of previously reported BWYV sequences (Table S2). Terminal sequences of the viral genome were analyzed by 5' and 3' rapid amplification of cDNA ends (RACE; Thermo Fisher Scientific Corp.). The assembled complete genome sequence of BWYV-NJ22 was 5,694 nt long and was deposited in GenBank (accession no. OQ625515). The Sanger sequences shared 96% nt identity with the HTS-derived sequence. BLASTn analysis showed that BWYV-NJ22 had high nucleotide identity (98%) at the complete genome level with a BWYV isolate (OL449448) from C. annuum in Korea. BWYV (genus Polerovirus, family Solemoviridae), is an aphid-borne virus with a host range that includes > 150 plant species and is one of the most important viruses causing yellowing and stunting of vegetable crops (Brunt et al., 1996; Duffus 1973). In Korea, BWYV was first reported to infect paprika, followed by pepper, motherwort, and figwort (Jeon et al., 2021; Kwon et al., 2016; 2018; Park et al., 2018). During fall and winter 2021, 675 radish plants with virus-like symptoms of mosaic, yellowing, and chlorosis were collected from 129 farms in major cultivation areas in Korea and analyzed by RT-PCR using the BWYV detection primers. The incidence of BWYV in radish plants was 4.7%, and all infections were mixed infections with TuMV. To our knowledge, this is the first report of BWYV infecting radish in Korea. The symptoms of single BWYV infection are unclear, as radish is a new host plant of BWYV in Korea. Further research on the pathogenicity and impact of this virus in radish is therefore needed.

First report of konjac mosaic virus in Spuriopimpinella brachycarpa in Korea.

Spuriopimpinella brachycarpa Nakai (Common name, Chamnamul; family Apiaceae) is a plant whose leaves are consumed as a vegetable and used as a folk medicine in Korea (Kim et al., 2020). In February 2020, seven samples of S. brachycarpa leaf showing virus symptoms including yellowing, vein chlorosis, chlorotic lesions, and severe mottling were collected from a greenhouse in Busan, South Korea, to diagnose the potential disease (Fig. S1a, b). The disease incidence rate in the greenhouse was >10% (2,970 m2). To identify the causal virus, we analyzed leaf dip preparation and thin sections of the symptomatic leaves by transmission electron microscopy. Filamentous virus particles and pinwheel structures were observed, indicating the presence of a potyvirus (Fig. S1c, d). To confirm these results, the symptomatic leaf samples were further analyzed by reverse-transcription polymerase chain reaction (RT-PCR) using potyvirus universal primers (Table S2) and direct sequencing of the PCR products. All samples were positive for konjac mosaic virus (KoMV). To exclude the possibility of infection by multiple viruses, we performed high-throughput sequencing (HTS) on an Illumina NovaSeq 6000 system (Macrogen Inc., Seoul, South Korea). There were two contigs (9,267 and 2,851 nt) mapping to KoMV sequences. A large contig (9,267 nt; 705,967 mapped reads; mean read coverage of 11,351.4x) showed about 80% identity (93% coverage) with KoMV-F (GenBank accession no. NC_007913) isolated from Amorphophallus konjac in Japan (Nishiguchi et al., 2006). To isolate KoMV from S. brachycarpa, we mechanically inoculated leaf extracts from symptomatic samples onto Chenopodium quinoa as an assay host via three single-lesion passages, followed by propagation in Nicotiana benthamiana. In a bioassay of the KoMV isolate (KoMV-BS), we mechanically inoculated sap from infected N. benthamiana onto 31 indicator plants including Cryptotaenia japonica (Apiaceae), which is similar to S. brachycarpa (Table S3). KoMV-BS systemically induced vein chlorosis and/or leaf mottling in four Nicotiana species and C. japonica, and chlorotic local lesions in upper leaves of C. quinoa; no symptoms were observed in 25 other indicator plants. These results were confirmed by RT-PCR. Next, we obtained the complete genome sequence of KoMV-BS using HTS and 5' and 3' rapid amplification of cDNA ends, with newly designed primers (Table S2). The assembled full-length KoMV-BS genome sequence was 9,392 nt in length, excluding the poly(A) tail, and encoded a polyprotein composed of 3,060 amino acids. The sequence was deposited in GenBank (accession no. OR001914). BLAST analysis showed 84~88% and 90~98% identities at CP nucleotide and amino acid levels, respectively with the reported KoMV isolates, confirming the virus to be an isolate of KoMV (synonym; Japanese hornwort mosaic virus, zantedeschia mosaic virus) (Adams et al., 2005; Nishiguchi et al., 2006). KoMV infection was first reported in A. konjac from Japan (Shimoyama et al. 1992) and has been spread worldwide as one of the major causal agents of viral diseases in calla lily (Liao et al., 2020). To the best of our knowledge, this is the first report of KoMV infection in S. brachycarpa. To date, cucumber mosaic virus and tobacco mosaic virus have been reported to infect S. brachycarpa in Korea (Yoon et al., 2016; 2017). Our findings will be helpful for developing virus-management strategies to prevent yield and quality loss in S. brachycarpa.

First report of Ranunculus mild mosaic virus in Ranunculus asiaticus in Korea.

Ranunculus (Ranunculus asiaticus L.) is a popular ornamental plant mainly cultivated for cut flowers and flowering potted plants. In January 2021, a leaf sample of R. asiaticus that showed virus-like symptoms including mosaic, yellowing and malformation on leaves was collected from a greenhouse in Jangheung, South Korea for disease diagnosis (Fig. S1). Disease incidence was greater than 30% in the greenhouse (~1,000 m2). Transmission electron microscopy (TEM) of symptomatic leaves identified potyvirus-like filamentous virus particles of about 800 nm. To confirm the TEM results, a symptomatic leaf sample was further analyzed by reverse-transcription polymerase chain reaction (RT-PCR) using species-specific detection primers for six potyviruses that infect R. asiaticus (Sacco et al., 2018). The sample was positive only for ranunculus mild mosaic virus (RanMMV). Additional analysis of nine symptomatic R. asiaticus plants from the infected greenhouse found that all samples were positive for RanMMV. To exclude the presence of the other viruses, next generation sequencing (NGS) was carried out. Total RNA was extracted from symptomatic leaves using the RNeasy Plant Mini Kit (Qiagen, Germany) and a transcriptome library was generated using the TruSeq Stranded Total RNA LT Sample Prep kit (Illumina, San Diego, CA) acccording to the recommended protocol. NGS was performed using an Illumina NovaSeq 6000 system (Macrogen Inc., Korea). A total of 75.58 million reads were obtained, and the reads were de novo assembled to contigs using Trinity software (Grabherr et al., 2011). BLASTn and BLASTx analysis of the contigs against the NCBI viral reference database identified the assembled large contig of 9,539 nt (5,321 mapped reads, mean read coverage of 84.2 times) as RanMMV. This sequence shared 98% nt identity (99% coverage) with the RanMMV NL isolate (acc. no. LC604020) isolated from an anemone plant (A. blanda cv. Charmer) from Netherlands. To obtain the complete genome sequence, the termini sequences were determined by 5' and 3' rapid amplification of cDNA ends (RACE) methods as reported recently (Imamura et al., 2021). The assembled full-length genome sequence of RanMMV-JH is 9,574 nt in length, excluding the poly(A) tail, and encoding a polyprotein of 3,074aa. The sequence was deposited in GenBank under the accession no. OL742438. RanMMV is transmitted by aphids in a nonpersistent manner and has very narrow host range. RanMMV, one of causative agents of ranunculus mosaic disease, has been problematic in ranunculus production area of Japan (Hayahi et al., 2018; Kamikawa et al., 2022). Recently, some perennial weeds from the Ranunculaceae family (e.g. R. japonicus, R. silerifolius and R. tachiroei) are known to may act as a virus reservoir (Kamikawa et al., 2022). As R. asiaticus is cultivated by vegetative propagation, there is need to develop certification system for producing virus-free R. asiaticus. To our knowledge, this is the first report of RanMMV infection in R. asiaticus in Korea.

First report of strawberry polerovirus 1 in strawberry in Nepal.

Strawberry (Fragaria x ananassa Duch.) was introduced to Nepal from Japan in the 1990s, and thus, is a relatively new crop in the country. After the initial introduction of cultivar 'Nyoho' in Kakani, Nuwakot, different agencies and growers have introduced a number of cultivars in large numbers from Japan, Europe, America and India to expand the cultivation of strawberry in Nepal. Such practice has increased the risk of introducing new pathogens in the country. During a field visit at Kakani in October 2018, virus-like symptoms were observed in 5-10% of the plants in a polyhouse (~200 m2). Three strawberry leaf samples showing vein banding, vein clearing or tip necrosis with leaf puckering were collected. Total RNA was extracted from leaves using the RNeasy Plant Mini Kit (Qiagen, Germany) and subjected to high-throughput sequencing (HTS). After ribosomal RNA depletion using the Ribo-Zero rRNA kit, a cDNA library was prepared using an Illumina TruSeq Stranded Total RNA Kit and sequenced on an Illumina NovaSeq 6000 system (Macrogen Inc. Korea). De novo transcriptome assembly of the 67,748,658 reads with Trinity software (r20140717) yielded 116,854 contigs of 201-17,773 nucleotides (nt). BLASTn and BLASTx analysis of the contigs against the NCBI viral reference database showed that one contig with the nearly full genome sequence (5,968 nt, deposited under GenBank accssion number MZ355624) was identified as strawberry polerovirus 1 (SPV-1). A total of 10,401 reads was mapped to the reference SPV-1 nucleotide genome (GenBank accession number NC_025435) with a 263.2 sequence depth. The contig shared 99% nt sequence identity with SPV-1 isolate AB5301 (GenBank accession number KM233705) from Canada and 97% identity with the Argentine SPV-1 isolate 15CA (GenBank accession number MK142237). To confirm the presence of SPV-1, reverse transcription-PCR (RT-PCR) was performed using previously reported specific primers, SPV-1F (AGAGATCGCCGGATTCCGCAA) and SPV-1R (TGACACGCTCGGTATTCACAAACAG), amplifying 281 nt of the P1-P2 fusion protein gene (Thekke-Veetil and Tzanetakis 2016). Of the three samples, only one showing vein banding symptoms (Figure S1) was positive for SPV-1. Sanger sequencing of the RT-PCR products showed 100% nt identity with the HTS-derived sequence. SPV-1, a member of the genus Polerovirus in the family Solemoviridae, was first reported in strawberry showing decline symptom in Canada (Xiang et al. 2015), and was subsequently detected in the USA (Thekke-Veetil and Tzanetakis 2016) and in Argentina (Luciani et al. 2016; 2018). To our knowledge, this is the first report of SPV-1 infection in strawberry in Nepal and Asia.

First report of cucurbit chlorotic yellows virus infecting cucumber in South Korea.

In October 2018, cucumber plants showing yellowing and chlorotic mottle symptoms were observed in a greenhouse in Chungbuk, South Korea. The observed symptoms were similar to those caused by cucurbit aphid-borne yellows virus (CABYV), which has been detected on cucumber plants in the region since it was reported on melon in Korea in 2015 (Lee et al 2015). To identify the potential agents causing these symptoms, 28 samples from symptomatic leaves and fruit of cucumber plants were subjected to total RNA extraction using the Plant RNA Prep Kit (Biocubesystem, Korea). Reverse transcription polymerase chain (RT-PCR) was performed on total RNA using CABYV specific primers and protocols (Kwak et al. 2018). CABYV was detected in 17 of the 28 samples, while 11 symptomatic samples tested negative. In order to identify the cause of the symptoms, RT-PCR was performed using cucurbit chlorotic yellows virus (CCYV) and cucurbit yellow stunting disorder virus (CYSDV) specific primers (Wintermantel et al. 2019). Eight of the 28 samples were positive using the CCYV specific primers while seven samples were infected with only CCYV and one contained a mixed infection of CABYV with CCYV. None of the samples tested positive for CYSDV. The expected 373 nt amplicons of CCYV were bi-directionally sequenced, and BLASTn analysis showed that the nucleotide sequences shared 98 to 100% identity with CCYV isolates from East Asia, including NC0180174 from Japan. Two pairs of primers for amplification of the complete coat protein and RNA-dependent RNA polymerase (RdRp) genes (Wintermantel et al., 2019) were used to amplify the 753bp coat protein and 1517bp RdRp genes, respectively. Amplicons of the expected sizes were obtained from a CCYV single infection and ligated into the pGEM T- Easy vector (Promega, WI, USA). Three clones from each amplicon were sequenced and aligned using Geneious Prime and found to have identical sequences (Genbank accession nos. MW033300, MW033301). The CP and RdRp sequences demonstrated 99% nucleotide and 100% amino acid identity with the respective genes and proteins of the CCYV isolates from Japan. This study documents the first report of CCYV in Korea. Since CCYV was first detected on melon in Japan, it has been reported in many other countries including those in East Asia, the Middle East, Southern Europe, North Africa, and recently in North America. CCYV has the potential to become a serious threat to production of cucurbit crops in Korea, particularly due to the increasing prevalence of the whitefly, Bemisia tabaci, in greenhouse production systems. It will be important to continue monitoring for CCYV and determine potential alternate hosts in the region to manage and prevent further spread of CCYV in Korea.

First report of Colombian datura virus in Brugmansia suaveolens in Korea.

Brugmansia suaveolens, known as angel's trumpet, is a perennial ornamental shrub in the Solanaceae with large fragrant flowers. In June 2018, a leaf sample of B. suaveolens that showed virus-like symptoms including chlorotic spots, yellowing and mottle on leaves was collected from a greenhouse in Seongnam, South Korea for disease diagnosis (Supplementary Figure S1a, b). Disease incidence in the greenhouse was greater than 80% for about 2,000 B. suaveolens plants. To identify a causal virus, transmission electron microscopy (TEM) was used to analyze symptomatic leaf samples using leaf dips and thin section methods. Filamentous virus particles and pinwheel structures were observed, indicating the presence of a potyvirus (Supplementary Figure S1c, d). To confirm the TEM results, a symptomatic leaf sample was further analyzed by reverse-transcription polymerase chain reaction (RT-PCR) using species-specific detection primers for three potyviruses that infect Brugmansia spp.: Colombian datura virus (CDV), Brugmansia mosaic virus (BruMV), and Brugmansia suaveolens mottle virus (BsMoV) (Lucinda et al, 2008; Park et al., 2014; Verma et al., 2014). The sample was positive only for CDV. CDV is transmitted by aphids in a nonpersistent manner and mechanical inoculation and can infect plants in the Solanaceae family including tomato and tobacco (Kahn and Bartels 1968; Schubert et al. 2006; Verhoeven et al. 1996) and has been designated a quarantine virus in Korea. Additional analysis of 13 symptomatic B. suaveolens plants from the infected greenhouse found that all samples except one were infected with CDV. To isolate CDV from B. suaveolens, leaf extracts from symptomatic samples were mechanically inoculated on an assay host, Nicotiana tabacum cv. BY via three single-lesion passages followed by propagation in N. benthamiana. For the bioassay of the CDV isolate (CDV-AT-Kr), sap from infected N. benthamiana was mechanically inoculated on 31 indicator plants, including B. suaveolens (Supplementary Table S2). CDV-AT-Kr induced chlorotic local lesions, necrotic local lesions, mottle, and/or mosaic systemically in 10 Nicotiana spp., and mottle and yellowing in tomato. On inoculated B. suaveolens, te mild mottle symptom was reproduced. No symptoms were observed in pepper or Datura stramonium. These results were confirmed by RT-PCR. To characterize CDV-AT-Kr genetically, the complete genome sequence of CDV-AT-Kr was obtained by RT-PCR using specific primers (Supplementary Table S3) and deposited in GenBank (accession no. MW075268). The CDV-AT-Kr RNA consists of 9,620 nt, encoding a polyprotein of 3,076 aa. BLASTn analysis showed that CDV-AT had maximum nucleotide identities of 98.9% at the complete genome level with a CDV isolate (accession no. JQ801448) from N. tabacum in the UK. To our knowledge, this is the first report of CDV infection in B. suaveolens in Korea and the second report in the world of the complete genome sequence. As B. suaveolens is cultivated by vegetative propagation, production and maintenance of virus-free, healthy B. suaveolens is needed. In addition, as new CDV hosts have been repeatedly reported (Pacifico et al., 2016; Salamon et al., 2015; Tomitaka et al., 2014; Verma et al., 2014), we are monitoring nationwide occurrence to prevent the spread of the virus to other crops.

First report of Tomato spotted wilt virus in Petasites japonicus in Korea.

Butterbur (Petasites japonicus [Siebold & Zucc.] Maxim.) is a perennial herb of the Asteraceae family that is cultivated for medicinal and nutritional purposes. Due to long-term vegetative propagation of virus-infected native species, the yield and quality of butterbur plants have deteriorated. Five viruses have been reported to infect this species: alfalfa mosaic virus (AMV), arabis mosaic virus (ArMV), butterbur mosaic virus (ButMV), broad bean wilt virus 2 (BBWV-2), and cucumber mosaic virus (CMV) (Ham et al. 2016; Tochihara and Tamura 1976). From 2018 to 2019, butterbur plants in four greenhouses in Nonsan, South Korea (Supplementary Figure S1a, b) were found to show virus-like symptoms such as chlorotic and necrotic ring spots, necrosis, and mild mosaic on the leaves. Disease incidence was greater than 80% in one greenhouse (~1,000 m2). To identify the causal virus, we collected 17 symptomatic butterbur leaf samples from these greenhouses and performed reverse-transcription polymerase chain reaction (RT-PCR) analysis using species-specific detection primers for the five reported viruses and tomato spotted wilt virus (TSWV) (Supplementary Table S2). RT-PCR results showed that 12 samples from three greenhouses showing necrotic ring spots and mosaic symptoms were infected with a mixture of TSWV and ButMV, whereas 5 samples from one greenhouse showing mild mosaic symptoms were infected only with ButMV. TSWV (genus Orthotospovirus, family Tospoviridae) is transmitted by thrips and causes serious damage to a wide range of economically important plants (Pappu et al. 2009). ButMV (genus Carlavirus, family Betaflexiviridae) is transmitted by aphids, as well as infected vegetative propagation material (Hashimoto et al. 2009) and is the most predominant virus in butterbur in Korea (Ham et al. 2016). To isolate TSWV from butterbur, leaf extracts from symptomatic samples were mechanically inoculated on an assay host, Chenopodium quinoa, via three single-lesion passages followed by propagation in Nicotiana tabacum cv. Samsun. Thirty different indicator plant species were used for the bioassay of the TSWV isolate (TSWV-NS-BB20) by mechanical inoculation method (Supplementary Table S3). RT-PCR analysis confirmed that TSWV-NS-BB20 induced necrotic local lesions and mosaic on Nicotiana species and ring spots and mosaic on tomatoes and peppers. Notably, TSWV-NS-BB20 reproduced necrotic local lesions and mild mosaic symptoms on butterbur plants which were infected with ButMV with no obvious symptoms. To characterize TSWV-NS-BB20 genetically, the complete genome sequences of L (8914 nt), M (4751 nt), and S (2917 nt) RNA segments were obtained by RT-PCR using specific primers for TSWV as described previously (Kwak et al., 2020). The obtained sequences were deposited in GenBank under accession nos. MT643236, MT842841, and MN854654, respectively. BLASTn analysis showed that sequences of each segment had maximum nucleotide identities of 99.0, 98.9, and 98.6% to TSWV-L, M, and S (KP008128, FM163373, and KP008129) of TSWV-LL-N.05 isolate from tomato in Spain. Since 2018, TSWV outbreaks on butterbur are observed every year and thus may act as a potential source of TSWV infection for other crops of importance to Korea, such as pepper. Owing to the butterbur vegetative propagation, the identification of TSWV infection in butterbur will be helpful for future virus management to generate virus-free materials. To our knowledge, this is the first report of TSWV infection of butterbur.

Identification of Viruses and Viroids Infecting Tomato and Pepper Plants in Vietnam by Metatranscriptomics.

Tomato (Lycopersicum esculentum L.) and pepper (Capsicum annuum L.) plants belonging to the family Solanaceae are cultivated worldwide. The rapid development of next-generation sequencing (NGS) technology facilitates the identification of viruses and viroids infecting plants. In this study, we carried out metatranscriptomics using RNA sequencing followed by bioinformatics analyses to identify viruses and viroids infecting tomato and pepper plants in Vietnam. We prepared a total of 16 libraries, including eight tomato and eight pepper libraries derived from different geographical regions in Vietnam. We identified a total of 602 virus-associated contigs, which were assigned to 18 different virus species belonging to nine different viral genera. We identified 13 different viruses and two viroids infecting tomato plants and 12 viruses and two viroids infecting pepper plants with viruses as dominantly observed pathogens. Our results showed that multiple infection of different viral pathogens was common in both plants. Moreover, geographical region and host plant were two major factors to determine viral populations. Taken together, our results provide the comprehensive overview of viral pathogens infecting two important plants in the family Solanaceae grown in Vietnam.

The complete genome sequence of a novel virus, bellflower veinal mottle virus, suggests the existence of a new genus within the family Potyviridae.

A new virus was isolated from a bellflower (Campanula takesimana) plant showing veinal mottle symptoms, and its complete genome sequence was determined. The viral genome consists of a positive-sense single-stranded RNA of 8,259 ribonucleotides. Electron microscopic observation revealed that the viral genome is packaged as a filamentous particle with an average length of approximately 760 nm. BLAST searches of protein databases showed that the encoded polyprotein has a maximum amino acid sequence identity of 34.1% (with 95% coverage) to that of the isolate AD of Chinese yam necrotic mosaic virus (CYNMV; genus Macluravirus). Phylogenetic analysis and comparison of the encoded amino acid sequences with those of other viruses demonstrated that the identified virus shows minimal sequence similarity to known viruses and should therefore be considered a member of a new genus in the family Potyviridae. The name bellflower veinal mottle virus (BVMoV) is proposed for this new virus.

Complete genome sequence of longan witches' broom-associated virus, a novel member of the family Potyviridae.

The complete genome sequence of a new virus isolated from a longan (Dimocarpus longan Lour.) plant showing witches' broom syndrome was determined. The viral genome is composed of a monopartite single-stranded RNA of 9,428 nucleotides excluding the 3' poly(A) tail and contains one large single open reading frame encoding a polyprotein of 3086 amino acids. BLAST searches of protein databases showed that the encoded polyprotein has a maximum amino acid sequence identity of 35% (with 85% coverage) to that of the isolate Minnesota of rose yellow mosaic virus (RoYMV; family Potyviridae; genus not assigned). Molecular and phylogenetic analysis of the genome and encoded protein sequences showed that the identified virus has the general features that are characteristic of members of the family Potyviridae although it has extremely low sequence similarity to known members of the family Potyviridae. The name longan witches' broom-associated virus (LWBaV) is proposed for this new virus, which may be considered a member of a new genus in the family Potyviridae.

Complete genome sequence of yacon necrotic mottle virus, a novel putative member of the genus Badnavirus.

The complete genome sequence of a previously undescribed virus isolated from a yacon plant exhibiting necrotic mottle, chlorosis, stunting, and leaf malformation symptoms in Gyeongju, Korea, was determined. The genome of this virus consists of one circular double-stranded DNA of 7661 bp in size. The genome contained four open reading frames (ORFs 1 to 4) on the plus strand that potentially encode proteins of 26, 32, 234, and 25 kDa. Protein BLAST analysis showed that ORF3, which is the largest ORF, has 45 % amino acid sequence identity (with 89 % coverage) to the ORF3 of fig badnavirus 1 (FBV-1), a recently identified badnavirus. Phylogenetic analysis provided further evidence that the virus identified in this study is probably a member of a new species in the genus Badnavirus. The name yacon necrotic mottle virus (YNMoV) is proposed for this new virus.

Complete genome sequence of bellflower vein chlorosis virus, a novel putative member of the genus Waikavirus.

The complete genome sequence of a new virus isolated from a bellflower (Campanula takesimana) plant was determined. The genome of this virus is composed of monopartite single-stranded RNA of 11,649 nucleotides in length. BLAST searches of protein databases showed that the encoded polyprotein has a maximum amino acid sequence identity of 42% (with 99% coverage) to the polyprotein of the isolate Orissa of rice tungro spherical virus (RTSV; genus Waikavirus). Phylogenetic analysis strongly supports that the identified virus is a member of a new species of the genus Waikavirus. The name bellflower vein chlorosis virus (BVCV) is proposed for this new virus.

Complete genome sequence of motherwort yellow mottle virus, a novel putative member of the genus Torradovirus.

The complete genome sequence of a new virus isolated from a motherwort plant exhibiting yellow mottle, mild mosaic, and stunting symptoms in Andong, Korea, was determined. The genome of this virus is composed of two single-stranded RNAs (7068 and 4963 nucleotides in length, respectively) carrying poly(A) tails. RNA1 contains one large open reading frame (RNA1-ORF1), while two potential ORFs (RNA2-ORF1 and RNA2-ORF2) were found in RNA2. BLAST searches of protein databases showed that RNA1-ORF1 and RNA2-ORF2 have maximum amino acid sequence identities of 53 % and 57 % to the RNA1-ORF1 and RNA2-ORF2, respectively, of lettuce necrotic leaf curl virus (LNLCV, a recently identified torradovirus). Phylogenetic analysis provided further evidence that the virus identified in this study is probably a member of a new species in the genus Torradovirus. The name "motherwort yellow mottle virus" (MYMoV) is proposed for this new virus.

Tomato yellow leaf curl virus Can Overwinter in Stellaria aquatica, a Winter-Hardy TYLCV-Reservoir Weed.

Tomato yellow leaf curl virus (TYLCV), one of the most serious plant viruses in tropical and subtropical regions, is transmitted to host plants by the vector insect Bemisia tabaci. In order to control TYLCV, it is important to identify weed hosts for overwintering TYLCV. Stellaria aquatica, a winter-hardy weed, was found growing with TYLCV-infected tomato plants in greenhouse production. TYLCV was detected in S. aquatica plants by polymerase chain reaction and Southern blot hybridization analysis. The intergenic region nucleotide sequences amplified from TYLCV-infected tomato plants, TYLCV-viruliferous whiteflies, and S. aquatica were identical. During winter (December to February), TYLCV-viruliferous whiteflies and TYLCV-infected tomato plants were removed or absent from greenhouses. However, S. aquatica plants were observed over a period of 10 months from August to May in such greenhouses, and TYLCV was consistently detected in some of these plants. To investigate the transmission of TYLCV from TYLCV-infected S. aquatica plants to healthy tomato plants by whiteflies, TYLCV-infected S. aquatica plants were transplanted to pots in cages with nonviruliferous whiteflies and healthy tomato plants. After 4 weeks, tomato plants developed typical TYLCV disease symptoms, and TYLCV was detected in both whiteflies and tomato plants. These results show that S. aquatica can act as a winter-hardy reservoir for TYLCV, and suggest that this weed could play an important role in overwintering of TYLCV in tomato greenhouses.

Lamium amplexicaule (Lamiaceae): a weed reservoir for tomato yellow leaf curl virus (TYLCV) in Korea.

After the first identification of tomato yellow leaf curl virus (TYLCV) in the southern part of Korea in 2008, TYLCV has rapidly spread to tomato farms in most regions of Korea. From 2008 to 2010, a survey of natural weed hosts that could be reservoirs of TYLCV was performed in major tomato production areas of Korea. About 530 samples were collected and identified as belonging to 25 species from 11 families. PCR and Southern hybridization were used to detect TYLCV in samples, and replicating forms of TYLCV DNA were detected in three species (Achyranthes bidentata, Lamium amplexicaule, and Veronica persica) by Southern hybridization. TYLCV transmission mediated by Bemisia tabaci from TYLCV-infected tomato plants to L. amplexicaule was confirmed, and TYLCV-infected L. amplexicaule showed symptoms such as yellowing, stunting, and leaf curling. TYLCV from infected L. amplexicaule was also transmitted to healthy tomato and L. amplexicaule plants by B. tabaci. The rate of infection of L. amplexicaule by TYLCV was similar to that of tomato. This report is the first to show that L. amplexicaule is a reservoir weed host for TYLCV.

Sweet pepper confirmed as a reservoir host for tomato yellow leaf curl virus by both agro-inoculation and whitefly-mediated inoculation.

Tomato yellow leaf curl virus (TYLCV), a member of the genus Begomovirus, has a single-stranded DNA genome. TYLCV can induce severe disease symptoms on tomato plants, but other hosts plants such as cucurbits and peppers are asymptomatic. A full-length DNA clone of a Korean TYLCV isolate was constructed by rolling-circle amplification from TYLCV-infected tomatoes in Korea. To assess relative susceptibility of sweet pepper varieties to TYLCV, 19 cultivars were inoculated with cloned TYLCV by agro-inoculation. All TYLCV-infected sweet peppers were asymptomatic, even though Southern hybridization and polymerase chain reaction analysis showed TYLCV genomic DNA accumulation in roots, stems, and newly produced shoots. Southern hybridization indicated that TYLCV replicated and moved systemically from agro-inoculated apical shoot tips to roots or newly produced shoots of sweet peppers. Whitefly-mediated inoculation experiments showed that TYLCV can be transmitted to tomatoes from TYLCV-infected sweet peppers. Taken together, these results indicate that sweet pepper can be a reservoir for TYLCV in nature.

Molecular genetic analysis of cucumber mosaic virus populations infecting pepper suggests unique patterns of evolution in Korea.

Studying genetic structure and diversity of viruses is important to understand the evolutionary mechanisms that generate and maintain variations in viral populations. Cucumber mosaic virus (CMV) is endemic in most pepper fields in Korea. Currently, no effective methods for control of CMV are available due to many environmental and biological factors such as the extensive evolutionary capacity of CMV. Thus, analyzing the genetic structure of CMV populations may facilitate the development of strategies for the control of CMV. In this study, 252 pepper (Capsicum annuum) samples showing virus symptoms were collected by field surveys performed throughout Korea in 2007. Reverse-transcription polymerase chain reaction analyses revealed that, in total, 165 collected samples were infected with CMV. Forty-five CMV isolates were randomly selected within each regional subpopulation and analyzed by full-genome sequencing. Analyses of genetic diversity showed that the 2b gene of CMV is under weaker purifying selection than the other genes. Based on the phylogenetic analysis of RNA1, the CMV isolates from pepper were divided into three clusters in subgroup I. Our full-genome sequence-based molecular analyses of the CMV Korean population suggest that the subpopulations of CMV have been geographically localized in pepper fields in Korea.

Occurrence and Multiplex PCR Detection of Citrus Yellow Vein Clearing Virus in Korea.

Citrus yellow vein clearing virus (CYVCV) is a member of the Alphaflexiviridae family that causes yellow vein clearing symptoms on citrus leaves. A total of 118 leaf samples from nine regions of six provinces in Korea were collected from various citrus species in 2020 and 2021. Viral diagnosis using next-generation sequencing and reverse transcription polymerase chain reaction (RT-PCR) identified four viruses: citrus tristeza virus, citrus leaf blotch virus, citrus vein enation virus, and CYVCV. A CYVCV incidence of 9.3% was observed in six host plants, including calamansi, kumquat, Persian lime, and Eureka lemon. Among the citrus infected by CYVCV, only three samples showed a single infection; the other showed a mixed infection with other viruses. Eureka lemon and Persian lime exhibited yellow vein clearing, leaf distortion, and water-soak symptom underside of the leaves, while the other hosts showed only yellowing symptoms on the leaves. The complete genome sequences were obtained from five CYVCV isolates. Comparison of the isolates reported from the different geographical regions and hosts revealed the high sequence identity (95.2% to 98.8%). Phylogenetic analysis indicated that all the five isolates from Korea were clustered into same clade but were not distinctly apart from isolates from China, Pakistan, India, and Türkiye. To develop an efficient diagnosis system for the four viruses, a simultaneous detection method was constructed using multiplex RT-PCR. Sensitivity evaluation, simplex RT-PCR, and stability testing were conducted to verify the multiplex RT-PCR system developed in this study. This information will be useful for developing effective disease management strategies for citrus growers in Korea.

Low-Temperature Nanosecond Laser Process of HZO-IGZO FeFETs toward Monolithic 3D System on Chip Integration.

Ferroelectric field-effect transistors (FeFETs) are increasingly important for in-memory computing and monolithic 3D (M3D) integration in system-on-chip (SoC) applications. However, the high-temperature processing required by most ferroelectric memories can lead to thermal damage to the underlying device layers, which poses significant physical limitations for 3D integration processes. To solve this problem, the study proposes using a nanosecond pulsed laser for selective annealing of hafnia-based FeFETs, enabling precise control of heat penetration depth within thin films. Sufficient thermal energy is delivered to the IGZO oxide channel and HZO ferroelectric gate oxide without causing thermal damage to the bottom layer, which has a low transition temperature (<250 °C). Using optimized laser conditions, a fast response time (<1 µs) and excellent stability (cycle > 106, retention > 106 s) are achieved in the ferroelectric HZO film. The resulting FeFET exhibited a wide memory window (>1.7 V) with a high on/off ratio (>105). In addition, moderate ferroelectric properties (2·Pr of 14.7 µC cm-2) and pattern recognition rate-based linearity (potentiation: 1.13, depression: 1.6) are obtained. These results demonstrate compatibility in HZO FeFETs by specific laser annealing control and thin-film layer design for various structures (3D integrated, flexible) with neuromorphic applications.

Complete genome sequence of keunjorong mosaic virus, a potyvirus from Cynanchum wilfordii.

We have determined the complete genome sequence of keunjorong mosaic virus (KjMV). The KjMV genome is composed of 9,611 nucleotides, excluding the 3'-terminal poly(A) tail. It contains two open reading frames (ORFs), with the large one encoding a polyprotein of 3,070 amino acids and the small overlapping ORF encoding a PIPO protein of 81 amino acids. The KjMV genome shared the highest nucleotide sequence identity (57.5  %) with pepper mottle virus and freesia mosaic virus, two members of the genus Potyvirus. Based on the phylogenetic relatedness to known potyviruses, KjMV appears to be a member of a new species in the genus Potyvirus.