• Mycobiology
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• v.34 no.2
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• pp.61-66
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• 2006

Chestnut blight disease caused by Cryphonectria parasitica is widely distributed throughout chestnut tree plantations in Korea. We surveyed 65 sites located at 9 provinces in South Korea, and isolated 248 virulent and 3 hypovirulent strains of chestnut blight fungus. Hypovirulent strains had dsRNA virus in the cytoplasm, which is one of the typical characteristics of hypovirulent strains. In addition, they showed more characteristics of hypovirulent strains, i.e., suppressed conidiation, reduced pigmentation in colony color, and reduced phenol oxidase activity as well as reduced pathogenicity. Hypovirulent strains, KCPH-22, KCPH-135 and KCPH-136, had a genomic dsRNA band with the molecular weight of 12.7 kb, which is the L-dsRNA of CHV1. They also had a 2.7 kb defective dsRNA band. Single conidia isolated from hypovirulent strains were cultured and various phenotypes and absence of dsRNA bands were obtained from single conidial cultures, which means that hypovirulence transmission is unstable in asexual reproduction and variations in viral heredity by asexual reproduction. Biocontrol trial using hypovirulent strains was also carried out in the chestnut tree plantations, and canker expansion in the treated trees was stopped and healed by callus formation at the margin of the canker. These results show the potentials in successful biocontrol of chestnut blight if the vegetatively compatible hypovirulent strains could be directly used around the canker formed by compatible virulent strains.

• The Plant Pathology Journal
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• v.18 no.1
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• pp.23-29
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• 2002

A total of 672 Cryphonectria parasitica was isolated from 2,536 blight lesions on chestnut twigs, which were collected from major chestnut plantations all over Korea. Isolation rates of each province ranged from 13.5% in Jeonbuk-ds to 37.4% in Gyeongnam-do, with an average rate of 25.6%. The isolates were classified into six groups according to color and shape of colony on PDA: smooth margin (S), irregular margin (I), yellow to brown (Y), white (W), and white with yellow center (C). Among these groups, IY was the most abundant with an isolation rate of 65%. On the other hand, SW, SC, IW, and SY were quite rare, with isolation rates ranging from 1.5% to 5.8%. When the 672 isolates were inoculated on the chestnut twigs,380 isolates (56.5%) caused lesions larger than the standard virulent isolate EPISS-2, while 158 isolates (23.4%) caused smaller lesions than the standard hypovirulent isolate UEP-1. However, 87.4% of the isolates belonged to the virulent group and only 12.6% belonged to the hypovirulent group based on Bavendamm test. In the provinces of Jeonnam-do, Jeonbuk-do, and Gyeongnamdo, which have high density of chestnut trees, the rates of hypovirulent-like isolates were over 20%.

• The Korean Journal of Mycology
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• v.25 no.3 s.82
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• pp.191-201
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• 1997

A mutant (HSMl) of Cryphonectria parasitica created during transformation reproduced the hypovirulent symptoms in virus-free wild type. Its phenomena have been proved with morphological marker such as reduced sporulation, pigmentation, and laccase production. In addition to the changes in phenotypic characteristics, down-regulations of Lac1, Crp1, Vir1 and Vir2 were also observed. The integration of transforming vector was confirmed and located within genome by marker rescuing. Vector integration occurred between two genes, Cpg2 and Cpg3, which resulted in the disruption of neither Cpg2 nor Cpg3. Both Cpg2 and Cpg3 genes, sized at 1.8 kb and 1.9 kb respectively, were rarely transcribed genes in Cryphonectria parasitica. Cpg2 expression was significantly overexpressed from 4 to 5 day old culture of both UEP1 and HSM1 while no differences were observed in Cpg3 expression. It appears that an aberration from the normal expression of Cpg2, not Cpg3, results in the hypovirulent symptoms in virus-free wild type.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2002.11a
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• pp.90.2-90
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• 2002

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2002.11a
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• pp.124.2-125
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• 2002

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1999.10a
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• pp.46.1-46
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• 1999

• The Plant Pathology Journal
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• v.16 no.3
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• pp.142-146
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• 2000

Ordered differential display using RT-PCR (ODD-PCR) was conducted to have a profile of the differently expressed genes between a hypovirulent strain of Cryphonectria parasitica (UEP1) and its isogenic wild type strain (EP155/2). ODD-PCR has advantages of high sensitivity, reproducibility, proportional representation, and limited number of primer combinations comparing with other differential display methods. RNAs were prepared from 1 and 5 day liquid culture of both hypovirulent and wild type strains, and were further evaluated with the marker genes of C. parasitica such as cryparin and mating factor MF2-1, which were already proven to be specifically down-regulated by the presence of mycovirus CHV1-713. ODD-PCR was conducted using those RNAs and expressed genes were categorized to five groups according to their temporal and quantitative expression patterns. Those fives groups are CPC, CPE, CPL, CPD, and CPU which represent constitutively-expressed, early-expressed, late-expressed, down-regulated, and up-regulated, respectively. Ninety two primer combinations out of a total of 192 have been tested so far. Among the twenty to fifty distinct bands per each reaction, an average of four to ten genes was identified as viral-regulated fungal genes. Those viral-specifc genes were further analyzed by DNA sequencing followed by homology search. Characterization of 30 clones including all five groups were conducted as a preliminary data and more are under investigation.

• Journal of Ginseng Research
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• v.47 no.6
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• pp.773-783
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• 2023

Background: Gray mold, caused by Botrytis cinerea, is one of the major fungal diseases in agriculture. Biological methods are preferred over chemical fungicides to control gray mold since they are less toxic to the environment and could induce the resistance to pathogens in plants. In this work, we try to understand if ginseng defense to B. cinerea could be induced by fungal hypovirulent strain △BcSpd1. BcSpd1 encodes Zn(II)₂Cys₆ transcription factor which regulates fungal pathogenicity and we recently reported △BcSpd1 mutants reduced fungal virulence. Methods: We performed transcriptomic analysis of the host to investigate the induced defense response of ginseng treated by B. cinerea △BcSpd1. The metabolites in ginseng flavonoids pathway were determined by UPLC-ESI-MS/MS and the antifungal activates were then performed. Results: We found that △BcSpd1 enhanced the ginseng defense response when applied to healthy ginseng leaves and further changed the metabolism of flavonoids. Compared with untreated plants, the application of △BcSpd1 on ginseng leaves significantly increased the accumulation of p-coumaric acid and myricetin, which could inhibit the fungal growth. Conclusion: B. cinerea △BcSpd1 could effectively induce the medicinal plant defense and is referred to as the biological control agent in ginseng disease management.

• Journal of Microbiology
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• v.44 no.5
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• pp.556-561
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• 2006

A differential display for the expression profiles of wild-type Cryphonectria parasitica and its virally-infected isogenic hypovirulent strain revealed several transcripts of interest, which evidenced significant matches with fungal genes of known function. Among which, we have further analyzed an amplified PCR product with significant sequence similarity to the known fungal stress-responsive thioredoxin gene from Neurospora crassa. The product of the cloned thioredoxin gene, CpTrx1, consists of 117 amino acids, with a predicted molecular mass of 13.0 kDa and a pI of 5.4. Sequence comparisons demonstrated that the deduced protein sequence of the CpTrx1 gene evidenced a high degree of homology to all known thioredoxins, with the highest degree of homology with trx1, a thioredoxin gene from Saccharomyces cerevisiae, and evidenced a preservation of the conserved hall markresidues (Trp-Cys-Gly-Pro-Cys) at the active site of thioredoxin. The E. coli-generated CpTRX1 manifested thioredoxin activity, according to the insulin reduction assay, which indicates that the cloned gene does indeed encode for the C. parasitica thioredoxin.

• The Plant Pathology Journal
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• v.19 no.1
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• pp.30-33
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• 2003

The chestnut blight fungus, Cryphonectria parasitica, and its hypovirus aye a useful model system in the study of the mechanisms of hypoviral infection and its consequences, such as a biological control of fungal pathogens. Strains containing the double-stranded (ds) RNA viruses Cryphonectria hypovirus 1 show characteristic symptoms of hypovirulence and display hypovirulence-associated changes, such as reduced pigmentation, sporulation, laccase production, and oxalate accumulation. Interestingly, symptoms caused by hypoviral infection appear to be the result of aberrant expression of a number of specific genes in the hypovirulent strain. Several viral regulated fungal genes are identified as cutinase gene, Lac1, which encodes an extracellular laccase, Crp, which encodes an abundant tissue-specific cell-surface hydrophobin that mediates physical strength, and Mf2/1 and Mf2/2, which encode pheromone genes involved in poor sporulation in the presence of hypo-virus. Since the phenotypic changes in the fungal host are pleiotropic, although coordinated and specific, it has been suggested that the hypovirus disturbs one or several regulatory pathways (Nuss,1996). Accordingly, several studies have shown the implementation of a signal transduction pathway during viral symptom development. Although further studies are required, hypovirulence and its associated symptom development due to the hypoviral regulation of a fungal hetero-trimeric G-protein have been suggested. In addition, recent studies have shown the presence of a novel protein kinase gene cppk1 and its transcriptional upregulation by hypovirus. In this review, the presence of important components in signal transduction pathway, their putative biological function, and viral-specific regulation will be addressed.