Sang-Hyun Koh

Fumigant toxicity and acetylcholinesterase inhibitory activity of 4 Asteraceae plant essential oils and their constituents against Japanese termite (Reticulitermes speratus Kolbe).

This study investigated the fumigant toxicity of 4 Asteraceae plant essential oils and their constituents against the Japanese termite Reticulitermes speratus Kolbe. Fumigant toxicity varied with plant essential oils or constituents, exposure time, and concentration. Among the tested essential oils, those from Chamaemelum nobile exhibited the strongest fumigant toxicity, followed by those from Santolina chamaecyparissus, Ormenis multicaulis, and Eriocephalus punctulatus at 2 days after treatment. In all, 15, 24, 19, and 9 compounds were identified in the essential oils from C. nobile, E. punctulatus, O. multicaulis, and S. chamaecyparissus, respectively, by using gas chromatography, gas chromatography-mass spectrometry, or open-column chromatography. The identified compounds were tested individually for their fumigant toxicity against Japanese termites. Among the test compounds, trans-pinocarveol, caryophyllene oxide, sabinene hydrate, and santolina alcohol showed strong fumigant toxicity against Japanese termites. Acetylcholinesterase (AChE) inhibition activity of the identified compounds from C. nobile, E. punctulatus, O. multicaulis, and S. chamaecyparissus essential oils were tested to determine the mode of their action. The IC50 values of (+)-α-pinene, (-)-limonene, (-)-α-pinene, β-pinene, and β-phellandrene against Japanese termite AChE were 0.03, 0.13, 0.41, 0.42, and 0.67mg/mL, respectively. Further studies are warranted to determine the potential of these essential oils and their constituents as fumigants for termite control.

Nematicidal activity of natural ester compounds and their analogues against pine wood nematode, Bursaphelenchus xylophilus.

In this study, we evaluated the nematicidal activity of natural ester compounds against the pine wood nematode, Bursaphelenchus xylophilus, to identify candidates for the development of novel, safe nematicides. We also tested the nematicidal activity of synthesized analogues of these ester compounds to determine the structure-activity relationship. Among 28 ester compounds tested, isobutyl 2-methylbutanoate, 3-methylbutyl 2-methylbutanoate, 3-methylbutyl tiglate, 3-methyl-2-butenyl 2-methylbutanoate, and pentyl 2-methylbutanoate showed strong nematicidal activity against the pine wood nematode at a 1 mg/mL concentration. The other ester compounds showed weak nematicidal activity. The LC50 values of 3-methylbutyl tiglate, isobutyl 2-methylbutanoate, 3-methylbutyl 2-methylbutanoate, 3-methyl-2-butenyl 2-methylbutanoate, and pentyl 2-methylbutanoate were 0.0218, 0.0284, 0.0326, 0.0402, and 0.0480 mg/mL, respectively. The ester compounds described herein merit further study as potential nematicides for pine wood nematode control.

A Combination of Biochemical and Proteomic Analyses Reveals Bx-LEC-1 as an Antigenic Target for the Monoclonal Antibody 3-2A7-2H5-D9-F10 Specific to the Pine Wood Nematode

Pine wilt disease (PWD) is one of the most devastating forest diseases in Asia and Europe. The pine wood nematode, Bursaphelenchus xylophilus, has been identified as the pathogen underlying PWD, although the pathology is not completely understood. At present, diagnosis and confirmation of PWD are time consuming tasks that require nematode extraction and microscopic examination. To develop a more efficient detection method for B. xylophilus, we first generated monoclonal antibodies (MAbs) specific to B. xylophilus. Among 2304 hybridoma fusions screened, a hybridoma clone named 3-2A7-2H5 recognized a single protein from B. xylophilus specifically, but not those from other closely related nematodes. We finally selected the MAb clone 3-2A7-2H5-D9-F10 (D9-F10) for further studies. To identify the antigenic target of MAb-D9-F10, we analyzed proteins in spots, fractions, or bands isolated from SDS-PAGE, two-dimensional electrophoresis, anion exchange chromatography, and immunoprecipitation via nano liquid chromatography electrospray ionization quadrupole ion trap mass spectrometry (nano-LC-ESI-Q-IT-MS). Peptides of galactose-binding lectin-1 of B. xylophilus (Bx-LEC-1) were commonly detected in several proteomic analyses, demonstrating that this LEC-1 is the antigenic target of MAb-D9-F10. The localization of MAb-D9-F10 immunoreactivities at the area of the median bulb and esophageal glands suggested that the Bx-LEC-1 may be involved in food perception and digestion. The Bx-LEC-1 has two nonidentical galactose-binding lectin domains important for carbohydrate binding. The affinity of the Bx-LEC-1 to d-(+)-raffinose and N-acetyllactosamine were much higher than that to l-(+)-rhamnose. Based on this combination of evidences, MAb-D9-F10 is the first identified molecular biomarker specific to the Bx-LEC-1.

Hazard rating of coastal pine forests for a black pine bast scale using self-organizing map (SOM) and random forest approaches

This study examined the effects of environmental factors on the abundance of black pine bast scale (BPBS), Matsucoccus thunbergianae Miller and Park, in coastal disaster prevention pine forests. Geographical factors, soil conditions and forest stand conditions were measured to evaluate the hazard rating for the occurrence of BPBS at 35 plots in the coastal forest stands. A combination of a self-organizing map (SOM), which classified the samples according to their characteristics, and a random forest model, which predicted the probability of the BPBS occurrence from SOM results, were used to assess the hazard rating. Our results showed that climate, tree size, and tree health are major factors determining the abundance of BPBS. BPBS was more common in low latitude coastal forests, suggesting that warmer conditions were favorable to BPBS population buildup. Tree size also influenced the abundance of BPBS, which was higher in forests composed of larger trees (greater DBH). Finally, BPBS was also more abundant in areas with high soil salinity and clay-loam soil, and north-facing slopes where tree vigor was lower. These results can provide useful information for improved coastal pine forests management against BPBS.

An empirical predictive model for the flight period of Platypus koryoensis (Coleoptera: Platypodinae)

Between 2007 and 2009, field studies were conducted in four Quercus mongolica Fischer ex Ledebour forests in Korea to develop an empirical degree-day model for the flight period of the ambrosia beetle, Platypus koryoensis (Murayama). The lower developmental threshold temperature was estimated using an iterative method based on field trap catches and temperatures. The pooled proportion of the total number of beetles found in the traps at the end of the experiment was plotted against the accumulated degree-days at selected baseline temperatures, and these plots were fitted by the Weibull function. The baseline temperature with the highest coefficient of determination was considered the lower developmental threshold temperature, and this was estimated to be 5.8xa0°C. The explanatory power of the model was 89xa0%. Moreover, the model accurately predicted the time distributions of P. koryoensis flights in 2011 and 2012 at one of the sites. The estimated median flight dates in 2011 and 2012 were 4xa0days earlier and 5xa0days later than the corresponding observed flight dates, respectively. The estimated median date of flight advanced progressively during 1970–2010 by a total of 9xa0days due to an increase in annual mean temperature.

Biological Characteristics of Sclerodermus harmandi (Hymenoptera: Bethylidae) Parasitized on Cerambycid

This study was performed to investigate the immature development period, fecundity, emergence rate and sex ratio of Sclerodermus harmandi against different host insects, Monochamus alternatus, M. saltuarius and Psacothea hilaris. Full grown larvae and pupae of host insects were provided with foods. The mean larval period of S. harmandi female was days in larvae and pupae of M. alternatus, days in M. saltuarius, and days in P. hilaris, respectively. S. hilaris adults were emerged at days in female and days in male after pupation when hosted M. alternatus pupa. Development period in male showed shorter one day than in female. Success rate of oviposition against different hosts was higher as 98.6 and 97.5% on full grown larva and pupa of M saltuarius. Emergence rate was higher as 90.1 and 87.3% on M. saltuarius larvae and pupae. Sex ratio of emerged S. harmandi adults was approximately 10:1 (Female : Male), females showed higher emergence rate than males. The period until first oviposition after emergence in S. harmandi female was the shortest in days on M. saltuarius pupa. When three females of S. harmandi were inoculated on M. saltuarius larva, the number of laid eggs was the highest per female.

Host–plant quality alters herbivore responses to temperature: a case study using the generalist Hyphantria cunea

The nutritional quality of host plants is an important determinant of fitness in insect herbivores. However, it remains an open question whether the ingestion of a particular plant will have the same effects on an herbivore under differing thermal conditions. We measured the performance of the generalist‐feeding caterpillars of Hyphantria cunea Drury (Lepidoptera: Arctiidae) raised on one of five natural host plants to determine their nutritional quality: Platanus occidentalis L. (Platanaceae), Sophora japonica (L.) Schott (Fabaceae), Prunus × yedoensis Matsum. (Rosaceae), Cornus kousa Hance (Cornaceae), or Betula platyphylla Sukaczev (Betulaceae). Caterpillars performed well on P. occidentalis, S. japonica, and P. × yedoensis, but poorly on C. kousa and B. platyphylla. The nutritional phenotype of caterpillars varied among host–plant groups, with the proportion of lipid‐free body mass to lipid content being higher for caterpillars raised on P. occidentalis and S. japonica (3.8–4.2:1) than for caterpillars raised on P. × yedoensis (1.6–2.1:1). A multi‐factorial experimental design was employed to investigate the interactive effects of host–plant quality and temperature on the performance of H. cunea caterpillars raised on either P. occidentalis or P. × yedoensis at three rearing temperatures (20, 25, or 30 °C). Caterpillars raised on P. occidentalis displayed a monotonic decrease in development time with increasing temperature, but the development time of those on P. × yedoensis decreased rapidly as temperature rose from 20 to 25 °C and then stayed unchanged despite further increase in temperature. The rate at which body size increased with decreasing temperature was much steeper for caterpillars raised on P. occidentalis than for those on P. × yedoensis. Collectively, these results indicate that host plant can alter the thermal reaction norms for the key life‐history traits of herbivores. This study has implications for understanding the impacts of climate change on herbivore–plant interactions.

Identification and Characterization of Expansins from Bursaphelenchus xylophilus (Nematoda: Aphelenchoididae)

Ilsong Institute of Life Science, Hallym University, Anyang 431-060, Korea(Received on August 7, 2012; Accepted on August 16, 2012)We identified two novel expansin (EXP) genes in theexpressed sequence tag database of Bursaphelenchusxylophilus, designated as Bx-EXPB2 and -EXPB3.Novel Bx-EXPBs encoded 150 amino acids and theirsimilarities in coding sequence were 70.7−84.0% to thepreviously reported EXPB1 of B. xylophilus. Bx-EXPB2and Bx-EXPB3 were clustered with Bx-EXPB1 and Bm-EXPB1, respectively, forming the independent phylo-geny with other nematode EXPs. All identified Bx-EXPBscontained the signal peptide and were only expressedduring the propagative stage, suggesting that they aresecreted to facilitate nematode migration through hostsby loosening cell walls during infection. Quantitativereal-time PCR analysis showed that the relative ac-cumulation of Bx-EXPB3 mRNAs was the highestamong the three Bx-EXPs examined and the order ofmRNA accumulation was as follows: Bx-EXPB3 > Bx-EXPB2 >> Bx-EXPB1. Homology modeling of Bx-EXPBs showed that the structurally optimum templatewas EXLX1 protein of Bacillus subtilis, whichsharedresidues essential for catalytic activity with Bx-EXPB1and Bx-EXPB2 except for Bx-EXPB3. Taken together,Bx-EXPB1 and Bx-EXPB2 may be involved migrationthrough plant tissues and play a role in pathogenesis.Keywords : Bursaphelenchus xylophilus, infections and propagation in host trees. expansin, homo-logy protein modeling, pathogenicity, pine wilt disease The pinewood nematode, Bursaphelenchus xylophilus isthe known agent causative of pine wilt disease (Mamiya,1975; Lee et al., 2011). Bursaphelenchus xylphilus areknown to be transferred from infected pine trees to newones by the pine sawyer beetle, Monochamus alternates(Mamiya, 1975). To express their potent phytopathogeni-city that is associated with infection and maintenance inthe host trees, B. xylophilus must overcome the physicalbarriers such as plant cell walls, which are mainly com-posed of polysaccharides, lipids, and proteins. The architectof plant cell wall is determined by cellulose, made of re-peating glucose molecules joined by β-1,4 glycosidic bonds(McQueen-Mason and Cosgrove, 1994; van den Brink andde Vries, 2011). The cellulose framework of the wall isinterpenetrated by a cross-linked matrix of non-cellulosemolecules, hemicelluloses, or pectin. Even though pinewoodnematode infected trees usually wither and die within acouple of months (Mamiya, 1975), we still do not understandthe molecular and cellular pathophysiology underlying theabilities of pinewood nematodes to infection and propagatein the trees. However, the presence of diverse cell walldegrading enzymes such as endoglucanases (Kikuchi et al.,2004; Smant et al., 1998), pectate lyases (Kikuchi et al.,2006; Popeijus et al., 2000) and expansins (EXPs) (Kikuchiet al., 2009) that to play crucial roles in initiation andprogression of the plant diseases are present in B. xylophilusgenomes suggested that secreted cell wall degrading enzymesfrom B. xylophilus may be important factors involved withEXPs in plants play pivotal roles in a wide variety ofdevelopmental processes by loosening of their cell walls byweakening non-covalent interactions (McQueen-Mason andCosgrove, 1994; McQueen-Mason and Cosgrove, 1995;Whitney et al., 2000), which makes cell walls susceptible todegradation and remodeling by other cell wall degradingenzymes (Cosgrove, 2000; van den Brink and de Vries,2011). While most EXPs were identified from plants, recentfindings that plant-parasitic nematodes express functionalEXPs suggested that they could be one of the major factorsregulating plant-parasite interactions (Qin et al., 2004; vanden Brink and de Vries, 2011). However, compared withEXPs in plants, the understanding of in vivo functions of

Antifungal activities after vaporization of ajowan (Trachyspermum ammi) and allspice (Pimenta dioica) essential oils and blends of their constituents against three Aspergillus species

Abstract The fumigant antifungal activities of ajowan (Trachyspermum ammi), and allspice (Pimenta dioica) essential oils and their constituents were tested against three Aspergillus species: A. ochraceus, A. parasiticus, and A. niger. Ajowan essential oil demonstrated a 100% inhibition rate against these three Aspergillus species at an air concentration of 56 × 10−3 mg/mL. The fumigant antifungal activities of allspice essential oil against A. niger, A. ochraceus, and A. parasiticus were 100, 84.4, and 83.5%, respectively. Gas chromatography-mass spectrometry analysis led to the identification of twelve compounds in ajowan oil and six compounds in allspice oil. Of the compounds tested, thymol, carvacrol, and eugenol showed strong inhibitory activity against the three Aspergillus species. The fumigant antifungal activities of blends of the constituents identified in ajowan and allspice oils indicated that thymol and eugenol were the major contributors to the fumigant antifungal activities of ajowan and allspice oils, respectively.

A Model for Predicting Spring Emergence of Monochamus saltuarius (Coleoptera: Cerambycidae) from Korean white pine, Pinus koraiensis.

ABSTRACT n Monochamus saltuarius Gebler is a vector that transmits the pine wood nematode, Bursaphelenchus xylophilus, to Korean white pine, Pinus koraiensis, in Korea. To reduce the damage caused by this nematode in pine forests, timely control measures are needed to suppress the cerambycid beetle population. This study sought to construct a forecasting model to predict beetle emergence based on spring temperature. Logs of Korean white pine were infested with M. saltuarius in 2009, and the infested logs were overwintered. In February 2010, infested logs were then moved into incubators held at constant temperature conditions of 16, 20, 23, 25, 27, 30 or 34°C until all adults had emerged. The developmental rate of the beetles was estimated by linear and nonlinear equations and a forecasting model for emergence of the beetle was constructed by pooling data based on normalized developmental rate. The lower threshold temperature for development was 8.3°C. The forecasting model relatively well predicted the emergence pattern of M. saltuarius collected from four areas in northern Republic of Korea. The median emergence dates predicted by the model were 2.2–5.9 d earlier than the observed median dates.