Kyu-Suk Kang

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.

Balancing Gene Diversity and Nut Production in Corylus avellana Collections

A theory on the balance between gene diversity and level of nut collection was developed and applied to Danish hazelnut (Corylus avellana L.) populations. By controlling female fertility based on the power function F(x)=x a, a trade-off between equalizing maternal contribution and obtaining an acceptable amount of nuts was achieved, and gene diversity during the initial phase of mobilizing the natural gene pool could be managed. Constraints on nut production could be made on maternal proportion as both lower and upper bounds. For a case involving the collection of hazelnuts from 264 individuals, the status number (N s) was estimated to be 149 based on female contribution if all nuts were collected and used. Higher status numbers could be obtained by balancing the number of nuts collected per tree, but such an increase in the status number would result in a substantial loss of nut production. It was decided to truncate the progeny size at 50 nuts, which required restriction of the nut contribution equally from the 14% most fertile individuals to a maximum contribution of 0.74%. This increased the N s from 149 to 201, while 85% of all nuts were included.

Effects of leaf nitrogen allocation on the photosynthetic nitrogen-use efficiency of seedlings of three tropical species in Indonesia

The leaf nitrogen (N) content (NL) and its allocation are major factors that determine the photosynthetic characteristics and photosynthetic N-use efficiency (PNUE) of tree species. In this study, we investigated the allocation of NL to the photosynthetic apparatus (NP) and its effects on the photosynthetic characteristics and PNUE of three tropical tree species (Magnolia montana Blume, Swietenia macrophylla King, and Acacia mangium Willd), which were grown in western Java, Indonesia. A. mangium (the only N-fixing species among three studied species) exhibited a greater NL and NP than other two species, resulting in higher capacities of photosynthetic parameters such as the light-saturated photosynthetic rate (Pmax), maximum carboxylation rate (VCmax), and maximum electronic transport rate (Jmax). However, S. macrophylla and A. mangium displayed a similar fraction of leaf N allocated to NP (NP/NL) and showed a higher NP/NL ratio than M. montana. Accordingly, S. macrophylla presented a higher PNUE than M. montana. Although A. mangium exhibited a similar PNUE to S. macrophylla, A. mangium showed a higher NL than the other two species, which resulted in a lower PNUE at a given NP. In addition, stomatal conductance was positively correlated with PNUE, but the slopes of the correlations between species presented a negative relationship with the leaf mass per area (LMA), which caused a longer pathway to the photosynthetic apparatus. Our results suggested that the variation of PNUE between species was affected by various factors, including the fraction of NL allocated to NP and morphological characteristics such as LMA.

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.

Estimation of genetic gain and diversity under various genetic thinning scenarios in a breeding seed orchard of Quercus acutissima

Genetic gain and diversity were estimated based on three simulated thinning scenarios at various thinning intensities in a breeding seed orchard of Quercus acutissima. The seed orchard was composed of 32 families with 744 individual trees with volume at age 15. The three thinning scenarios were individual thinning (IT) which thinning was based on the individual performance, family thinning (FT) with the removal of inferior families regardless of individual performance, and family + within family thinning (FWF) with family first and then individual from inferior families. The genetic gain was estimated based on stem volume. Expected genetic gain (volume at age 15) under IT was higher than FT and FWF at all thinning intensities. The FWF provided higher genetic gain than FT but lower than IT. The FT gave the lowest genetic gain compared to the other thinning scenarios at all thinning intensities. The loss of gene diversity (GD), estimated by coancestry and family size, was higher under FWF and lower under FT at moderate thinning intensities. The study showed that genetic gain estimation and GD loss were inversely coupled. The IT gave highest genetic gain but lowest GD at the highest thinning intensity.