• The Plant Pathology Journal
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• v.34 no.6
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• pp.470-479
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• 2018

The rice blast pathogen Magnaporthe oryzae is a global threat to rice production. Here we characterized RHO2 gene (MGG_02457) that belongs to the Rho GTPase family, using a deletion mutant. This mutant ${\Delta}Morho2$ exhibited no defects in conidiation and germination but developed only 6% of appressoria in response to a hydrophobic surface when compared to the wild-type progenitor. This result indicates that MoRHO2 plays a role in appressorium development. Furthermore, exogenous cAMP treatment on the mutant led to appressoria that exhibited abnormal morphology on both hydrophobic and hydrophilic surfaces. These outcomes suggested the involvement of MoRHO2 in cAMP-mediated appressorium development. ${\Delta}Morho2$ mutation also delayed the development of appressorium-like structures (ALS) at hyphal tips on hydrophobic surface, which were also abnormally shaped. These results suggested that MoRHO2 is involved in morphological development of appressoria and ALS from conidia and hyphae, respectively. As expected, ${\Delta}Morho2$ mutant was defective in plant penetration, but was still able to cause lesions, albeit at a reduced rate on wounded plants. These results implied that MoRHO2 plays a role in M. oryzae virulence as well.

• The Plant Pathology Journal
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• v.18 no.5
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• pp.284-287
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• 2002

The antifungal activity of super reductive water (SRW) against plant pathogenic fungi was examined to extend its application to integrated pest management (IPM) for plant diseases. Diluted solutions ($\times$1/10, $\times$1/25, and $\times$1/50) of SRW inhibited fungal growth of kiwifruit soft rot pathogen, Diaporthe actinidiae, in a concentration dependent manner, When kiwifruits were inoculated on wounds with mycelium blocks, stock and diluted solutions successfully inhibited the disease development. In addition to the high pH of the SRW, fungistatic activity was also considered as the cause of the antifungal effect against the pathogen. Whereas conidial germination of Magnaporthe grisea was not affected by the diluted SRW solutions, appressorium formation was significantly inhibited in a concentration dependent manner, With little harmfulness to human health and environment SRW could be used to control plant pathogenic fungi, particularly appressorium-forming fungal pathogens.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2005.10a
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• pp.63-64
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• 2005

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1999.04a
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• pp.37.2-38
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• 1999

• The Plant Pathology Journal
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• v.38 no.4
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• pp.345-354
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• 2022

NADPH oxidase (Nox) complexes are known to play essential roles in differentiation and proliferation of many filamentous fungi. However, the functions of Noxs have not been elucidated in Colletotrichum species. Therefore, we set out to characterize the roles of Nox enzymes and their regulators in Colletotrichum scovillei, which causes serious anthracnose disease on pepper fruits in temperate and subtropical and temperate region. In this study, we generated targeted deletion mutants for CsNox1, CsNox2, CsNoxR, and CsNoxD via homologous recombination. All deletion mutants were normal in mycelial growth, conidiation, conidial germination, and appressorium formation, suggesting that CsNox1, CsNox2, CsNoxR, and CsNoxD are not involved in those developmental processes. Notably, conidia of 𝜟Csnox2 and 𝜟Csnoxr, other than 𝜟Csnox1 and 𝜟Csnoxd, failed to cause anthracnose on intact pepper fruits. However, they still caused normal disease on wounded pepper fruits, suggesting that Csnox2 and CsnoxR are essential for penetration-related morphogenesis in C. scovillei. Further observation proved that 𝜟Csnox2 and 𝜟Csnoxr were unable to form penetration peg, while they fully developed appressoria, revealing that defect of anthracnose development by 𝜟Csnox2 and 𝜟Csnoxr resulted from failure in penetration peg formation. Our results suggest that CsNox2 and CsNoxR are critical for appressorium-mediated penetration in C. scovillei-pepper fruit pathosystem, which provides insight into understanding roles of Nox genes in anthracnose disease development.

• Research in Plant Disease
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• v.23 no.1
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• pp.42-48
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• 2017

Chlorella is one of the microorganisms which can live autotrophically by their own photosynthesis. It was previously revealed that pre-treatment of Chlorella fusca caused a suppression of appressorium formation on the cucumber leaves after inoculation with Colletothrichum orbiculare. In this study, the ultrastructures of C. orbiculare on the cucumber leaves pretreated with C. fusca were observed using both scanning electron microscope (SEM) and transmission electron microscope (TEM). The SEM images revealed that most fungal conidia and hyphae were attached with lots of C. fusca cells. Also, the conidia could germinate but not form appressorium, which is necessary to penetrate into host tissue. These observations suggested that C. fusca adjoined to the fungus may play a role in suppression of the appressorium formation. On the other hand, the observations of TEM showed no remarkable cytological differences on the ultrastructures of the intracellular hyphae between in the pre-treated and untreated leaves. It seemed that the fungus could grow in the pre-treated plant tissues as in the untreated one. Based on these observations, it is suggested that the suppression of appressorium on the leaf surfaces by the C. fusca cells may be a main cause of the reduction of the anthracnose disease.

• The Plant Pathology Journal
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• v.17 no.6
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• pp.378.1-378
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• 2001

• Korean Journal of Microbiology
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• v.22 no.1
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• pp.19-28
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• 1984

The nematode-trapping process by Arthrobotrys conoides was investigated with the aid of scanning and transmission electron microscopy. 1. A. conoides captures nematode by means of three-dimensional network. 2. The wall of trap cell was thicker than that of vegetative hypha and the trap cell was more rich in cell organelles such as endoplasmic reticulum, mitochondria and electrondense granule. 3. The electron-dense granule, which could be found only in trap organs, gradually disappeared during its penetration into nematode cuticle. 4. The osmiophilic area was found at adhering site between the trap organ and nematode cuticle. 5. In some cases, any appressorium was not found at the site of penetration. 6. When the fungal-nematode culture was conserved for 2~3 weeks, numerous young nematodes were found to be adhered to spores, resulting in death.

• Mycobiology
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• v.51 no.3
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• pp.178-185
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• 2023

The cell wall integrity (CWI) signaling pathway plays important roles in the dissemination and infection of several plant pathogenic fungi. However, its roles in the pepper fruit anthracnose fungus Colletotrichum scovillei remain uninvestigated. In this study, the major components of the CWI signaling pathway-CsMCK1 (MAPKKK), CsMKK1 (MAPKK), and CsMPS1 (MAPK)-were functionally characterized in C. scovillei via homology-dependent gene replacement. The ΔCsmck1, DCsmkk1, and ΔCsmps1 mutants showed impairments in fungal growth, conidiation, and tolerance to CWI and salt stresses. Moreover, ΔCsmck1, ΔCsmkk1, and ΔCsmps1 failed to develop anthracnose disease on pepper fruits due to defects in appressorium formation and invasive hyphae growth. These results suggest that CsMCK1, CsMKK1, and CsMPS1 play important roles in mycelial growth, conidiation, appressorium formation, plant infection, and stress adaption of C. scovillei. These findings will contribute to a better understanding of the roles of the CWI signaling pathway in the development of pepper fruit anthracnose disease.

• Research in Plant Disease
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• v.22 no.4
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• pp.257-263
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• 2016

Chlorella is known as chlorophyceae which can live autotrophically by photosynthesis, promote the growth of plants and suppress some plant diseases. However, a few researches in inhibition mechanism of plant diseases by chlorella have been carried out. In this study cucumber leaves pre-treated with Chlorella fusca suspension were investigated whether anthracnose by Colletotrichum orbiculare is suppressed or not. Furthermore, in order to illustrate how the algae can restrain the antracnose, the infection structures of C. orbiculare were observed on the cucumber leaves pre-treated with the algae. Consequently, appressorium formation rate was apparently reduced in the cucumber leaves pre-treated with C. fusca compared to untreated control one. Also, the numbers of conidia found at the inoculation sites were significantly reduced compared to untreated one. On the other hand, on the leaves pre-treated with $Benomyl^{(R)}$ appressorium formation were decreased remarkably and numbers of conidia were also reduced similar with those pre-treated with C. fusca. Based on these results, it was revealed that occurrence of anthracnose can be suppressed by C. fusca pre-treatment and suggested that biochmical or structural hinderance by C. fusca resulting in the decline of appressorium formation on the leave surfaces may play an important role in the disease suppression.