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.

Plastid methylerythritol phosphate pathway participates in the hypersensitive response-related cell death in .

Programmed cell death (PCD), a characteristic feature of hypersensitive response (HR) in plants, is an important cellular process often associated with the defense response against pathogens. Here, the involvement of , a gene encoding 4-hydroxy-3-methylbut-2-enyl diphosphate reductase that participates in the final step of the plastid methylerythritol phosphate (MEP) pathway, in plant HR cell death was studied. In plants, silencing of the gene using virus-induced gene silencing (VIGS) caused plant growth retardation and albino leaves with severely malformed chloroplasts.

First report of Mochi tree (Ilex integra) Anthracnose caused by Colletotrichum fioriniae in Korea.

Ilex integra, also called Mochi tree, is an woody ornamental common in Asia, particularly in Korea, China, Japan, and Taiwan. Anthracnose, caused by Colletotrichum spp., is an economically important disease worldwide, affecting both fruit and seed quality.

Effect on Colony Growth Inhibition of Soil-Borne Fungal Pathogens by Available Chlorine Content in Sodium Hypochlorite.

Our study investigated the available chlorine content, contact time and difference among strains of each pathogen for sodium hypochlorite (NaOCl) to control chemically against soil-borne fungal pathogens, such as Phytophthora rot by , violet root rot by , and white root rot by , causing die-back symptom on apple trees. As a result, the colony growth of was inhibited completely by soaking over 5 s in 31.25 ml/l available chlorine content of NaOCl.

Biological Control of Meloidogyne incognita by Aspergillus niger F22 Producing Oxalic Acid.

Restricted usage of chemical nematicides has led to development of environmentally safe alternatives. A culture filtrate of Aspergillus niger F22 was highly active against Meloidogyne incognita with marked mortality of second-stage juveniles (J2s) and inhibition of egg hatching. The nematicidal component was identified as oxalic acid by organic acid analysis and gas chromatography-mass spectroscopy (GC-MS).

Nematicidal activities of 4-quinolone alkaloids isolated from the aerial part of Triumfetta grandidens against Meloidogyne incognita.

The methanol extract of the aerial part of Triumfetta grandidens (Tiliaceae) was highly active against Meloidogyne incognita, with second-stage juveniles (J2s) mortality of 100% at 500 μg/mL at 48 h post-exposure. Two 4-quinolone alkaloids, waltherione E (1), a new alkaloid, and waltherione A (2), were isolated and identified as nematicidal compounds through bioassay-guided fractionation and instrumental analysis. The nematicidal activities of the isolated compounds against M.

First Report of Cucumber mosaic virus Isolated from Wild Vigna angularis var. nipponensis in Korea.

A viral disease causing severe mosaic, necrotic, and yellow symptoms on Vigna angularis var. nipponensis was prevalent around Suwon area in Korea. The causal virus was characterized as Cucumber mosaic virus (CMV) on the basis of biological and nucleotide sequence properties of RNAs 1, 2 and 3 and named as CMV-wVa.

Molecular Characterization and Variation of the Broad bean wilt virus 2 Isolates Based on Analyses of Complete Genome Sequences.

The full-genome sequences of fourteen isolates of Broad bean wilt virus 2 (BBWV2), collected from broad bean, pea, spinach, bell pepper and paprika plants in Korea during the years 2006-2012, were determined and analyzed comparatively along with fifteen previously reported BBWV2 genome sequences. Sequence analyses showed that RNA-1 and RNA-2 sequences of BBWV2 Korean isolates consisted of 5950-5956 and 3568-3604 nucleotides, respectively. Full-length genome sequence-based phylogenetic analyses revealed that the BBWV2 Korean isolates could be divided into three major groups comprising GS-I (isolates BB2 and RP7) along with isolate IP, GS-II (isolates BB5, P2, P3 and RP3) along with isolate B935, and GS-III including 16 BBWV2 Korean isolates.

Genetic Compositions of Broad bean wilt virus 2 Infecting Red Pepper in Korea.

The incidence of Broad bean wilt virus 2 (BBWV2) on red pepper was investigated using the samples obtained from 24 areas of 8 provinces in Korea. Two hundred and five samples (79%) out of 260 collected samples were found to be infected with BBWV2. While the single infection rate of BBWV2 was 21.

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.

Recent trends in studies on botanical fungicides in agriculture.

Plants are attacked by various phytopathogenic fungi. For many years, synthetic fungicides have been used to control plant diseases. Although synthetic fungicides are highly effective, their repeated use has led to problems such as environmental pollution, development of resistance, and residual toxicity.

Biological function of a novel chrysovirus, CnV1-BS122, in the Korean Cryphonectria nitschkei BS122 strain.

Curing Cryphonectria nitschkei BS122 of a novel chrysovirus CnV1-BS122 infection was achieved by plating small hyphal fragments from an old plate and protoplasting followed by regeneration. Uneven distribution of mycoviruses within colonies was suggested. Comparing the CnV1-BS122-cured and -infected isogenic strains revealed that CnV1-BS122 infection resulted in reduced mycelial growth.

Potent in vivo antifungal activity against powdery mildews of pregnane glycosides from the roots of Cynanchum wilfordii.

Two new pregnane glycosides, kidjoranine 3-O-β-D-glucopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 4)-α-L-cymaropyranosyl-(1 → 4)-β-D-cymaropyranosyl-(1→4)-α-L-diginopyranosyl-(1 → 4)-β-D-cymaropyranoside (5) and caudatin 3-O-β-D-glucopyranosyl-(1 → 4)-β-D-glucopyranosyl-(1 → 4)-α-L-cymaropyranosyl-(1 → 4)-β-D-cymaropyranosyl-(1 → 4)-α-L-diginopyranosyl-(1 → 4)-β-D-cymaropyranoside (6), were isolated from the roots of Cynanchum wilfordii along with four known compounds (1-4). The antifungal activities of the six compounds against barley powdery mildew caused by Blumeria graminis f. sp.

Nucleotide sequences of four segments of chrysovirus in Korean Cryphonectria nitschkei BS122 strain.

The near full-length genome consisting of four segments of dsRNA from a chrysovirus infecting Korean Cryphonectria nitschkei BS122 strain (CnV1-BS122) was sequenced. The open reading frames of segments 1, 2, 3, and 4 were 2,889, 2,721, 2,475, and 2,232 nucleotides (nt) in length, respectively. Sequence analysis and homology searches of the amino acid sequences deduced from the ORFs of each segment revealed that segments 1, 2, 3, and 4 encoded RNA-dependent RNA polymerase, capsid protein, a putative cysteine protease, and replication-associated protein, respectively.

Molecular diversity of chrysoviruses in Korean isolates of a new fungal species, Cryphonectria nitschkei.

Genetic diversity of the chrysovirus within the four fungal strains was analyzed by comparing the full-length sequences of cloned chrysoviral genes encoding the RNA-dependent RNA polymerase (RdRp) and capsid protein (CP). Because the morphological characteristics of four chrysovirus-infected Cryphonectria spp. strains were different, strain identification was conducted via sequence comparison of the internal transcribed spacers (ITSs) of the fungal rRNA gene.

A tannic acid-inducible and hypoviral-regulated Laccase3 contributes to the virulence of the chestnut blight fungus Cryphonectria parasitica.

A new laccase gene (lac3) from the chestnut blight fungus Cryphonectria parasitica was induced by the presence of tannic acid, which is abundant in the bark of chestnut trees and is assumed to be one of the major barriers against pathogen infection. However, other commonly known laccase inducers, including ferulic acid, 2,5-xylidine, catechol, and pH, did not induce lac3 transcription. Moreover, the hypovirus modulated the induction of lac3 transcription, abolishing the transcriptional induction of the lac3 gene by tannic acid.

Occurrence of diverse dsRNA in a Korean population of the chestnut blight fungus, Cryphonectria parasitica.

We analysed 676 isolates from 33 Korean Cryphonectria parasitica subpopulations in Korea for dsRNA incidence and diversity. dsRNA was detected in 84 isolates. Although the dsRNA banding patterns varied in several minor bands, infected isolates could be categorized into two groups.

A gene encoding phosphatidyl inositol-specific phospholipase C from Cryphonectria parasitica modulates the lac1 expression.

Hypovirus infection of the chestnut blight fungus Cryphonectria parasitica is known to downregulate the fungal laccase1 (lac1), the modulation of which is tightly governed by the inositol triphosphate (IP(3)) and calcium second messenger system in a virus-free strain. We cloned the gene cplc1 encoding a phosphatidyl inositol-specific phospholipase C (PLC), to investigate the regulation of lac1 expression and to better characterize fungal gene regulation by hypovirus. Sequence analysis of the cplc1 gene indicated that the protein product contained both the X and Y domains, which are the two conserved regions found in all known PLCs, with a 133 amino acid extension between the 2nd beta-strand and the alpha-helix in the X domain.

Characterization of the ERK homologue CpMK2 from the chestnut blight fungus Cryphonectria parasitica.

The Cryphonectria parasitica gene cpmk2, which encodes a mitogen-activated protein kinase belonging to the yeast extracellular signalling-regulated kinase (YERK1) subfamily, was isolated and its biological function was examined. Disruption of cpmk2 resulted in impaired pigmentation and abolished conidiation. Growth defects were observed in the cpmk2 mutant grown on solid plates, but growth of the mutant appeared normal in liquid media, including EP complete and PD broth, suggesting that the cpmk2 gene is involved in sensing and responding to growth conditions.

Deletion of a hypoviral-regulated cppk1 gene in a chestnut blight fungus, Cryphonectria parasitica, results in microcolonies.

The cppk1 gene encodes a Ser/Thr protein kinase of Cryphonectria parasitica and is transcriptionally up-regulated by the presence of hypovirus CHV1-EP713. A cppk1-null mutant was constructed to determine the function of cppk1. The cppk1-null mutant was initially isolated as a heterokaryotic form containing both wild-type and cppk1-deleted nuclei.

Characterization of HOG1 homologue, CpMK1, from Cryphonectria parasitica and evidence for hypovirus-mediated perturbation of its phosphorylation in response to hypertonic stress.

We examined the biological function of cpmk1, which encodes a MAPK of Cryphonectria parasitica, and its regulation by mycovirus. Sequence comparisons revealed that cpmk1 had highest homology with osm1, a hog1-homologue from Magnaporthe grisea. A growth defect was observed in the cpmk1-null mutant under hyperosmotic conditions, indicating that cpmk1 functionally belongs to a hog1 subfamily.

Characterization of a fungal protein kinase from Cryphonectria parasitica and its transcriptional upregulation by hypovirus.

The chestnut blight fungus Cryphonectria parasitica and its hypovirus comprise useful model system to study the mechanisms of hypoviral infection. We used degenerate primers based on fungal protein kinases to isolate a gene, cppk1, which encodes a novel Ser/Thr protein kinase of C. parasitica.