• The Plant Pathology Journal
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• v.28 no.4
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• pp.409-417
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• 2012

We identified two novel expansin (EXP) genes in the expressed sequence tag database of Bursaphelenchus xylophilus, designated as Bx-EXPB2 and -EXPB3. Novel Bx-EXPBs encoded 150 amino acids and their similarities in coding sequence were 70.7-84.0% to the previously reported EXPB1 of B. xylophilus. Bx-EXPB2 and Bx-EXPB3 were clustered with Bx-EXPB1 and Bm-EXPB1, respectively, forming the independent phylogeny with other nematode EXPs. All identified Bx-EXPBs contained the signal peptide and were only expressed during the propagative stage, suggesting that they are secreted to facilitate nematode migration through hosts by loosening cell walls during infection. Quantitative real-time PCR analysis showed that the relative accumulation of Bx-EXPB3 mRNAs was the highest among the three Bx-EXPs examined and the order of mRNA accumulation was as follows: Bx-EXPB3 > Bx-EXPB2 >> Bx-EXPB1. Homology modeling of Bx-EXPBs showed that the structurally optimum template was EXLX1 protein of Bacillus subtilis, whichshared residues essential for catalytic activity with Bx-EXPB1 and Bx-EXPB2 except for Bx-EXPB3. Taken together, Bx-EXPB1 and Bx-EXPB2 may be involved migration through plant tissues and play a role in pathogenesis.

• The Plant Pathology Journal
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• v.23 no.4
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• pp.318-321
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• 2007

Pine wood nematode, Bursaphelenchus xylophilus, causes pine wilt disease in a number of Pinus species, which is one of the most serious plant diseases in forest, Korea. In the course of a search for nematicidal substances from endophytic fungi, Fusarium oxysporum EF119 out of the 23 fungal strains tested showed the strongest activity to B. xylophilus. Two nematicidal substances were isolated and identified as bikaverin and fusaric acid. Fusaric acid showed somewhat higher nematicidal activity against B. xylophilus than bikaverin; fusaric acid and bikaverin, at $100{\mu}g/ml$, killed B. xylophilus with mortality values of 50% and 43%, respectively. In addition, both compounds acted synergistically. This is the first report on the nematicidal activity of bikaverin and fusaric acid.

• Journal of Korean Society of Forest Science
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• v.104 no.3
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• pp.512-518
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• 2015

Pine wilt disease (PWD) caused by pine wood nematode, Bursaphelenchus xylophilus, has become the most serious threat to pine trees in Korea. This study was subjected to investigate effective biological control agent against PWD. To select nematocidal bacteria against PWD, Bacillus licheniformis MH48 was selected among five bacteria due to its high nematocidal potential. B. licheniformis MH48 was tested for cell growth and protease activity to evaluate its nematicidal potential. In the B. licheniformis MH48, cell numbers were highest three days after incubation, while protease activity was highest after seven days. In the effect of different concentrations of B. licheniformis MH48 culture broth against B. xylophilus, 20% concentration of culture broth showed approximately 80% of pine wood nematode mortality compared to the control. Especially, pine wood nematode's cuticle layers were degraded two days after treatment of B. licheniformis MH48 culture broth. The present study suggests that B. licheniformis MH48 can be one of the potential biocontrol candidates against pine wood nematode due to its ability to produce protease.

• Molecules and Cells
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• v.26 no.2
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• pp.171-174
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• 2008

Flavone (2-phenyl chromone) is a well-known plant flavonoid, but its bioactivity has been little explored. Treatment of Caenorhabditis elegans or C. brissage with flavones induced embryonic and larval lethality that was pronounced in early larval stages. This anti-nematodal effect was also observed in the pinewood nematode, B. xylophilus. $LD_{50}$ values were approximately $100{\mu}M$ for both B. xylophilus and C. elegans. Our results indicate that flavone is an active nematicidal compound that should be further investigated with the aim of developing a potent drug against B. xylophilus.

• The Plant Pathology Journal
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• v.25 no.3
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• pp.241-246
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• 2009

Korean pine (Pinus koraiensis Sieb. et Zucc.), a five-needle pine, has recently been suffering pine wilt disease caused by non-native pinewood nematode, Bursaphelenchus xylophilus. Three-year-old Korean pine seedlings were inoculated with 10,000 pathogenic nematodes in a greenhouse to investigate disease development, water content and the density of nematodes in stems. Needle dehydration, xylem drying and pith browning started 20 days after inoculation (DAI). There were significant differences between seedlings inoculated with nematodes and control seedlings in the relative water content of stems and leaves at 20 and 30 DAI. At 60 DAI, all remaining seedlings inoculated with nematodes had died, but control seedlings all remained alive. The average number of nematodes recovered from stems of Korean pine dramatically increased from 10 to 20 DAI, and then decreased at the end of the experiment at 60 days. This study suggests that the relative water content of stems and leaves in current-year branches could be used as a useful physiological indicator for early diagnosis of pine wilt disease.

• Journal of Forest and Environmental Science
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• v.36 no.3
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• pp.255-258
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• 2020

Pine wilt disease (PWD) caused by pine wood nematode (PWN), Bursaphelenchus xylophilus, which is transmitted by Monochamus alternatus and M. saltuarius, is a serious threat to coniferous forests in the Northern Hemisphere, including Korea. The efficacy of abamectin and emamectin benzoate for preventing the PWD in the field and its effect on the vectors Monochamus alternatus and M. saltuarius (Coleoptera: Cerambycidae) were evaluated. An experimental plot was delimited, of which consists of Japanese red pine (Pinus densiflora) forest in South Korea, and trunk injection trials were made with abamectin and emamectin benzoate. Branches of each tree were collected, and are subsequently subjected to the analysis of residues for both nematicides. Results obtained in this study showed that abamectin and emamectin benzoate showed over 90% mortality at the recommended concentration after 6 days and 8 days, respectively. Consequently, it was found that both insecticides have a higher effect on the susceptibility and persistence of two vectors of PWD, M. alternatus and M. saltuarius feeding on branches of the trees, and its application by trunk injection is confirmed as an option for pine wilt disease management programs in Korea.

• Journal of Digital Contents Society
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• v.18 no.1
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• pp.191-195
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• 2017

In this study, a smartphone application for reporting trees infected with pine wilt disease was developed to prevent the spread of the disease by the disease-carrying pests/insects, which is most damning to the country's pine trees, South Korea's representative tree species, and to ensure the sustained maintenance of the country's forest trees. Such application for handling information on the infected pine trees has three key components, as shown below. (1) Explanation of the pine wilt disease pests/insects, (2) Image capture of the infected pine tree, and transmission of its GPS location, (3) Inquiry on the neighboring area infected with pine wilt disease. It is possible to promptly provide the spatial information of the areas infected with pine wilt disease by developing a dedicated application for reporting trees infected with the disease based on GPS information. If users participate actively in the application and integration with the forest service application is to be realized, the application would be more actively utilized.

• Journal of Korean Society of Forest Science
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• v.94 no.5 s.162
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• pp.334-337
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• 2005

Pine wood nematode isolates from Haman, Gyoungsangnam-do were cryopreserved with three different cryoprotectants (glycerol, ethylene glycol and dimethylsulfoxide), Nematode Growth medium (NGM) and M 9 buffer solution, respectively, and then survival rate, reproduction ability, and pathogenicity of stored nematodes were compared. Survival rates of juvenile was excellent in 15% glycerol solution as $72{\pm}5.3%$. The survival ability of nematodes at juvenile stage was more efficient than that of nematodes at adult stage. Pre-incubation treatment at $4^{\circ}C$ before storing in liquid nitrogen didn't affect the survival ability of pine wood nematode. When the reproduction ability of nematodes was confirmed on Botrytis cinerea agar plates at $28^{\circ}C$ incubator, there was no difference between cryopreserved and non-cryopreserved. Pathogenic ability of cryopreserved nematodes was also evaluated and confirmed by artificially inoculating them on 2-year old red pine seedlings.

• The Plant Pathology Journal
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• v.32 no.4
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• pp.340-346
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• 2016

To understand how Bursaphelenchus xylophilus kills pine trees, the differences between the effects of B. xylophilus and B. mucronatus on pine trees are usually compared. In this study, the migration and attacking ability of a non-pathogenic B. mucronatus in Pinus thunbergii were investigated. The distribution of B. mucronatus and the number of dead epithelial cells resulting from inoculation were compared with those of the pathogenic B. xylophilus. Although B. mucronatus is non-pathogenic in pines, its distribution pattern in P. thunbergii was the same as that of B. xylophilus. We therefore concluded that the non-pathogenicity of B. mucronatus could not be attributed to its migration ability. The sparse and sporadic attacking pattern of B. mucronatus was also the same as that of B. xylophilus. However, the number and area of the dead epithelial cells in pine cuttings inoculated with B. mucronatus were smaller than in those cuttings inoculated with B. xylophilus, meaning that the attacking ability of B. mucronatus is weaker than that of B. xylophilus. Therefore, we concluded that the weaker attacking ability of B. mucronatus might be the factor responsible for the non-pathogenicity.

• The Plant Pathology Journal
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• v.29 no.3
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• pp.344-349
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• 2013

Intraspecific variation in morphometry of pine wood nematodes Bursaphelenchus xylophilus and B. mucronatus in relation to geographical locations in South Korea was investigated using morphometric characters (body length, a, b and c ratio, stylet length, and spicule length for a male nematode and V (%) value for a female nematode). B. xylophilus was isolated from Pinus thunbergii in Jinju (1998), Ulsan (2000), Yangsan (2000), Mokpo (2001) and Jeju (2004), and from P. densiflora in Gumi (2001). B. mucronatus was isolated from P. thunbergii in Jinju (1991) and from P. densiflora in Milyang (2001). The body length of male and female B. xylophilus had the highest coefficient of variability and showed significant differences among geographical locations. The V (%) value for female B. xylophilus showed the lowest coefficient of variability, changing little with geographical area and host plant. All morphometric characters in B. mucronatus except for stylet length and female body length showed no significant differences between locations or hosts, suggesting they may not be affected by geographical area or host plant.