• The Korean Journal of Mycology
• /
• v.47 no.4
• /
• pp.417-425
• /
• 2019

Biocontrol agents (BCAs) are widely used to protect plants from diverse biotic and abiotic stresses in agricultural and ecological fields. Among the various microbes, many subspecies of the gram-positive genus, Bacillus, have been successfully industrialized as eco-friendly biological pesticides and fertilizers. In the current study, we demonstrated that Bacillus thuringiensis C25 exhibited antagonistic effects on the mycelial growth of Rosellinia necatrix, a fungal phytopathogen. Scanning electron microscopy analysis revealed that B. thuringiensis C25 degraded the cell wall structures of R. necatrix mycelia. In the functional genomic analysis of B. thuringiensis C25, we annotated 5,683 genes and selected the gene sets that potentially encoded fungal cell wall degrading enzymes (CWDEs). The growth inhibition effects on R. necatrix were highly correlated with the transcriptional activity of the mycelial cell wall degrading genes of B. thuringiensis C25. The transcript levels of CWDEs, including CshiA, B, and Glycos_transf_2 genes in B. thuringiensis C25, were enhanced following co-cultivation with R. necatrix. In conclusion, our study suggested that B. thuringiensis C25 could serve as a suitable candidate for controlling R. necatrix and could facilitate elucidating the mechanisms underlying the antifungal activities of BCAs against phytopathogens.

• Plant Disease and Agriculture
• /
• v.1 no.1
• /
• pp.37-44
• /
• 1995

This study was carried out to select effective fungicides against white and violet root rot caused by Rosellinia necatrix and Helicobasidium mompa with nine fungicides including thiophanate-methyl from 1993 to 1994. Through laboratory, greenhouse and field trials on inhibitory effect of mycelial growth and disease incidence against the two fungal pathogens, 5 fungicides have been selected finally. Thiopanate-methyl, benomyl, iminoctadine-triacetate and isoprothiolane were proven to have high control effect against R. necatrix. In addition to thiopanate-methyl and benomyl, tolclofos-methyl has been selected for effective control of H. mompa, since it showed prominent control effect in field trial than in laboratory or green house test.

• Research in Plant Disease
• /
• v.15 no.1
• /
• pp.46-50
• /
• 2009

Cytochalasin E (CE) is a secondary metabolite secreted by Rosellinia necatrix, caused by white root rot, and has toxicity to apple as a toxin during disease progress. This study was conducted to demonstrate the relationship between the production of CE and its pathogenicity. CE producing isolates and non-producing isolates of R. nectatrix were isolated from the mycerial mat of diseased roots and was detected on that using a TLC and HPLC analysis and in vivo pathogenicity test. CE non-producing isolates were not pathogenic to apple roots and not detected CE by TLC and HPLC analysis. It was shown that the production of CE was related to the pathogenicity of R. nectatrix.

• The Plant Pathology Journal
• /
• v.33 no.4
• /
• pp.362-369
• /
• 2017

White root rot disease, caused by the pathogen Rosellinia necatrix, is one of the world's most devastating plant fungal diseases and affects several commercially important species of fruit trees and crops. Recent global outbreaks of R. necatrix and advances in molecular techniques have both increased interest in this pathogen. However, the lack of information regarding the genomic structure and transcriptome of R. necatrix has been a barrier to the progress of functional genomic research and the control of this harmful pathogen. Here, we identified 10,616 novel full-length transcripts from the filamentous hyphal tissue of R. necatrix (KACC 40445 strain) using PacBio single-molecule sequencing technology. After annotation of the unigene sets, we selected 14 cell cycle-related genes, which are likely either positively or negatively involved in hyphal growth by cell cycle control. The expression of the selected genes was further compared between two strains that displayed different growth rates on nutritional media. Furthermore, we predicted pathogen-related effector genes and cell wall-degrading enzymes from the annotated gene sets. These results provide the most comprehensive transcriptomal resources for R. necatrix, and could facilitate functional genomics and further analyses of this important phytopathogen.

• The Plant Pathology Journal
• /
• v.19 no.3
• /
• pp.152-158
• /
• 2003

Stromata of the white root rot fungus, Rosellinia necatrix, were produced on diseased roots although they were reported to develop rarely in nature. Forty-two (42) out of 47 samples produced synnemata while 23 developed stromata. Forty-seven (47) isolates obtained from diseased root samples were divided into 24 mycelium compatibility groups (MCGs). Sixteen (16) out of 24 MCGs produced stromata. Single ascospore isolates from 10 stroma samples produced dsRNA-containing isolates from diseased tissue beneath stromata. The frequency of synnema production on axenic culture varied among isolates with different origin. The dsRNA was not transmitted vertically to the ascospore offspring despite the infection of various dsRNA in the parental isolates. The dsRNA was absent in 35 ascospore isolates in two stroma samples that originated from the isolates, in which dsRNA was not eliminated by hyphal tip isolation. Consequently, sexual reproduction in the white root rot fungus was suggested to produce propagules as a new infection source and to have the function to eliminate infectious factors such as mycoviruses.

• Research in Plant Disease
• /
• v.27 no.3
• /
• pp.91-98
• /
• 2021

The current social demand for organic, sustainable, and eco-friendly approaches for farming, while ensuring the health and productivity of crops is increasing rapidly. Biocontrol agents are applied to crops to ensure biological control of plant pathogens. Research on the biological control of white root rot disease caused by a soil-borne pathogen, Rosellinia necatrix, is limited in pears compared to that in apple and avocado. This pathogenic fungus has an extensive host range, and symptoms of this disease include rotting of roots, yellowing and falling of leaves, wilting, and finally tree death. The severity of the disease caused by R. necatrix, makes it the most harmful fungal pathogen infecting the economical fruit tree species, such as pears, and is one of the main limiting factors in pear farming, with devastating effects on plant health and yield. In addition to agronomic and cultural practices, growers use chemical treatments to control the disease. However, rising public concern about environmental pollution and harmful effects of chemicals in humans and animals has facilitated the search for novel and environmentally friendly disease control methods. This review will briefly summarize the current status of biocontrol agents, ecofriendly methods, and possible approaches to control disease in pear orchards.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2002.11a
• /
• pp.93.1-93
• /
• 2002

• Korean Journal of Organic Agriculture
• /
• v.5 no.1
• /
• pp.137-147
• /
• 1996

For the purpose of acquiring microbial agents that can be utilized to biologically control the major airborne diseases to apple trees, such as canker(Botryosphaeria dothidea), bitter rot(Glomerella cingulata), alternaria leaf spot(Alternaria mali), root rot(rosellinia necatrix), canker(Valsa ceratosperma) and gray mold rot(Botrytis cinerea), the effective microorgaisms were isolated, tested for antagonistic activity to the pathogens causing major diseases to apple trees and identifed. Screening of more than 5,000 species of microorganisms collected in nature for them antagonistic action to the pathogens causing 5 major diseases to apple trees resulted in selection of effective species. Out of the 11 species, one species designated as CAP134 demonstrated outstanding activity. The bacterial strain, CAP134 exerted antagonistic efficiency of 57% on an isolated strain and 40% on a donated strain of Botryosphaeria dothidea., 52% on an isolated strain and 46% on a purchased strain of Alternaria mali, 60% on Valsa ceratosperma 25% on Glomerella cingulata, and 64% Rosellinia necatrix. The CAP134 was identified as a bacterial strain to Bacillus subtilis ATCC 6633 based on morephology, culture conditions, and physio-biochemical characteristics.

• Research in Plant Disease
• /
• v.9 no.1
• /
• pp.42-46
• /
• 2003

Conidiomata of the Rosellinia necatrix were induced in axenic culture under near ultraviolet light radiation. Pieces of sterilized Japanese pear twigs were placed on the 7 days-old oatmeal agar culture in plates. The plates were further incubated far 5 days and then illuminated by under near ultraviolet light radiation. Syn-nemata were developed on twigs in 19 out of 20 isolates tested within 5 weeks, and conidia were observed in 12 out of the 19 isolates. The synnemata and conidia produced were morphologically identical to those of Dematophora necatrix.

• The Plant Pathology Journal
• /
• v.35 no.2
• /
• pp.156-163
• /
• 2019

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 Phytophthora cactorum, violet root rot by Helicobasidium mompa, and white root rot by Rosellinia necatrix, causing die-back symptom on apple trees. As a result, the colony growth of Phytophthora cactorum was inhibited completely by soaking over 5 s in 31.25 ml/l available chlorine content of NaOCl. Those of H. mompa and R. necatrix were inhibited entirely by soaking over 160 s in 62.5 and 125 ml/l available chlorine content in NaOCl, respectively. Also, inhibition effect on available chlorine in NaOCl among strains of each soil-borne pathogen showed no significant difference and was similar to or better than that of fungicides.