Zorica Popović

Larvicidal and antifeedant activity of some plant-derived compounds to Lymantria dispar L. (Lepidoptera: Limantriidae)

Ethanol solutions of essential oil of Ocimum basilicum and its main component, linalool (both isomer forms), all in three concentrations, as well as botanical standard Bioneem (0.5%), were tested for their toxicity and antifeedant activity against the second instar gypsy moth larvae in the laboratory bioassay. The essential oil of O. basilicum was subjected to gas chromatography analysis, and totally 37 compounds were detected, of which linalool was predominantly present. All tested solutions showed low to moderate larvicidal effect in both residual toxicity test and in chronic larval mortality bioassay. Chronic mortality tests showed that obtained mortality was a consequence of starving rather than ingestion of treated leaves. However, antifeedant index achieved by application of tested solutions in feeding choice assay was remarkable. Foliar application of all tested compounds deterred feeding by L2 in the same percent as Bioneem. Antifeedant index was relatively high at all tested treatments (85-94%); moreover, the larval desensitization to repelling volatiles has not occurred after five days of observation. Low toxic and high antifeedant properties make these plant-derived compounds suitable for incorporation in integrated pest management programs, especially in urban environments.

Josephson effect and spin-triplet pairing correlations in SF1F2S junctions

We study theoretically the Josephson effect and pairing correlations in planar SF1F2S junctions that consist of conventional superconductors (S) connected by two metallic monodomain ferromagnets (F1 and F2) with transparent interfaces. We obtain both spin-singlet and -triplet pair amplitudes and the Josephson current-phase relations for arbitrary orientation of the magnetizations using the self-consistent solutions of Eilenberger equations in the clean limit and for a moderate disorder in ferromagnets. We find that the long-range spin-triplet correlations cannot prevail in symmetric junctions with equal ferromagnetic layers. Surprisingly, the long-range spin-triplet correlations give the dominant second harmonic in the Josephson current-phase relation of highly asymmetric SF1F2S junctions. The effect is robust against moderate disorder and variations in the layers thickness and exchange energy of ferromagnets.

Population density of Diabrotica virgifera virgifera LeConte beetles in Serbian first year and continuous maize fields

A 5‐year field survey examined western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte) beetle density in Serbia from 2002 to 2006. First‐, second‐, third‐, fourth‐ and fifth‐year maize fields were sampled; they represented 64.61%, 21.66%, 9.45%, 3.53% and 0.75% of all sampled fields respectively. Results showed that the mean WCR beetle population density from 794 maize fields differed depending on cropping history. Minimum mean WCR/trap/day was 0.0 in the first‐year maize fields in 2002 and 2006. Maximum mean WCR/trap/day was registered in the fourth‐year and the fifth‐year maize fields (27.8 and 21.2 respectively). Mean population density of WCR adults increased with the number of years of continuous maize from 1.17, 4.61, 6.41, 10.30 up to 13.53 WCR/trap/day for first‐fifth‐year maize fields respectively. Mean WCR/trap/day ± SE exceeded the economic population threshold of >6 WCR/trap/day in third‐year continuous maize fields. Out of 794 maize fields, 697 (87.78%) registered a mean population density below the <6 beetles/trap/day threshold. In only 97 fields was WCR population density >6 beetles/trap/day, a finding that predicts a risk of economic damage to a subsequent maize planting. These data are representative of the Serbian situation from 2002 to 2006; they indicate that WCR are well dispersed across commercial maize fields in Serbia. These results provide new insight into the current low WCR population densities in maize fields managed by crop rotation, a finding that can help in creating long‐term management strategy.

Sand topography influences the distribution of xerohalophytic vegetation on a southern Adriatic beach in Montenegro

Abstract Totally, 26 xerohalophytic species belonging to the associations Cakilo-Xanthietum italici and Echinophoro-Elymetum farcti were registered at the Velika plaža beach (Montenegro); they were distributed following the spatial succession common in this type of habitat. Three transects of different terrain morphology (positioned perpendicularly to the shoreline) were surveyed to establish if there were any differences in the floristic composition and species distribution due to the configuration discrepancy. Moreover, each transect was divided into zones: The first zone from 0 to 30 m inland, the second zone from 30 m to 60 m inland, and the third zone from 60 m to the end of beach (75–115 m, depending on transect length). The floristic composition was relatively uniform in the different transects. However, the number of individuals per species differed significantly among these transects. An analysis of the qualitative composition of transects/zones showed high differences between zones within transects I and II, whereas species composition of zones within transect III was mostly similar. When analyzing the quantitative composition of species, a positive correlation between the distance from the shoreline and the number of individuals per species in transects I and II was registered for most analyzed species (Spearman correlation, p < 0.001). This indicates that terrain configuration affected the ability of present species to become established and propagate.

Ecologically Acceptable usage of Derivatives of Essential Oil of Sweet Basil, Ocimum basilicum, as Antifeedants Against Larvae of the Gypsy Moth, Lymantria dispar

Abstract Ethanol solutions of five fractions obtained from essential oil of sweet basil Ocimum basilicum L. (Lamiales: Lamiaceae) (F1–F5) were tested for their antifeedant properties against 2nd instar gypsy moth larvae, Lymantria dispar L. (Lepidoptera: Lymantriidae), in laboratory non-choice and feeding-choice experiments. Prior to bioassays, the chemical composition of each fraction was determined by gas chromatography analyses. Significant larval deterrence from feeding was achieved by application of tested solutions to fresh leaves of the host plant. The most effective were were F1 (0.5%), F4 (0.05, 0.1, and 0.5%), and F5 (0.1 and 0.5%), which provided an antifeedant index > 80% after five days. A low rate of larval mortality was observed in no-choice bioassay. In situ screening of chlorophyll fluorescence as an indicator of plant stress level (assessed by the induced fluorometry) confirmed that the tested compounds did not cause alternations in the photosynthetic efficiency of treated leaves.

Significance of diarylheptanoids for chemotaxonomical distinguishing between Alnus glutinosa and Alnus incana

Abstract Diarylheptanoids are a group of secondary metabolites widely distributed in the Betulaceae family and characteristic for Alnus species. In this study, the chemotaxonomic power of diarylheptanoids, such as hirsutanonol-5-O-β-d-glucopyranoside, rubranoside A, oregonin, platyphylloside, alnuside A and hirsutanonol, has been investigated in combination with principal component analysis (PCA) for differentiation of Alnus species. Concentrations of six diarylheptanoids in the bark extracts of two natural populations of Alnus glutinosa (black alder) and Alnus incana (gray alder) were determined by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). PCA clearly shows the separation of three groups. Populations I (A. glutinosa) and II (A. incana) both consisted of individuals of the corresponding species. Four individuals from both sampled populations formed a separate group (population III), which possibly represents a hybrid group. Accordingly, diarylheptanoids may serve in combination with PCA as chemotaxonomic markers at the species level, which may also reveal hybrid species.

Quasiparticle Transport Properties of d-Wave Superconductor/Ferromagnet/d-Wave Superconductor Junctions

Solving the time-dependent Bogoliubov–de Gennes equations, we calculate current–voltage characteristics (CVC) and conductances (G) of clean d-wave superconductor/ferromagnet/d-wave superconductor (DFD) junctions with transparent D/F interfaces. Due to the suppression of Andreev reflection (AR) by the exchange energy \(h\) in the ferromagnetic barrier and by the presence of gap nodes in the d-wave superconductor electrodes, there is a striking difference in shape and amplitude of CVC with respect to the case of isotropic s-wave superconducting banks. This provides an indication of the superconductor order parameter symmetry. The influence of AR is much better seen in the conductance dependence on the bias voltage \(G(V)\). The conductance curves have a rich nonlinear structure in low-voltage multiple AR region. At higher voltages, the curves are almost flat, with characteristic dips located at \(eV=[2\Delta(T)\mp h]/n\), with n=1, 2, ..., Δ(T) being the maximum order parameter at the temperature \(T\). Obs...

Geographic variability of selected phenolic compounds in fresh berries of two Cornus species

Key messageThe contents of quercetin glycosides and neochlorogenic acid in fresh berries of Cornelian cherry and Common dogwood were assessed through LC–MS/MS analysis to determine chemical differentiation between two distant populations of each species.AbstractThe aim of this study was to investigate the chemical variability of Cornus mas and Cornus sanguinea on the basis of the content of six selected phenolic compounds in fruit extracts. Fruits were sampled at the time of full ripening, mid-September, from two localities that differed in terms of orographic and environmental conditions. Fresh fruit extracts were analyzed by LC–MS/MS to determine the presence and contents of neochlorogenic acid, quercitrin, isoquercetin, hyperoside, rutoside and querciturone. While all of the tested compounds were detected in both species, their content was several times higher in C. sanguinea. Locality-dependent differences were tested by appropriate statistical tests, which confirmed that the contents of all compounds significantly differed in C. mas, whereas the content of only one compound differed in C. sanguinea. Differences between populations were also revealed by PCA analyses. Both species showed clear separation of populations based on the analyzed phenolic compounds. The results showed that a specific environment can significantly affect the contents of certain secondary metabolites, as in the case of C. mas, and/or that the synthesis of these compounds can be to a lesser extent influenced by external factors, as in the case of C. sanguinea.

Chemical Composition and Interpopulation Variability of Essential Oils of Taxus baccata L. from Serbia

The composition of the essential oil of the twigs and needles of Taxus baccata L. from three natural populations in Serbia has been determined by GC/MS analysis. Of the 91 detected compounds, 87 were identified. The most abundant compound classes were aliphatic alcohols, terpenes, aliphatic hydrocarbons, and aliphatic aldehydes, which together comprised ca. 86.92% of the total oil composition. The dominant constituents were oct‐1‐en‐3‐ol (23.48%), (3Z)‐hex‐3‐en‐1‐ol (11.46%; aliphatic alcohols), and myrtenol (11.38%; oxygenated monoterpene). The PCA of 22 selected compounds revealed differentiations of populations based on geographic distribution. The CA showed that Populations I and II from the Dinaric Alps were similar, and that Population III from the Balkan mountain system was distinct. This was the first investigation of interpopulation variability of T. baccata populations based on essential oil composition. The results of this study were compared with those of previous studies concerning volatile compounds produced by Taxus species. The results indicate that the essential oil content of T. baccata populations from this study is unique, mostly resembling the population from southeast Serbia.

Essential-Oil Variability in Natural Populations of Pinus mugo Turra from the Julian Alps.

The composition and variability of the terpenes and their derivatives isolated from the needles of a representative pool of 114 adult trees originating from four natural populations of dwarf mountain pine (Pinus mugo Turra) from the Julian Alps were investigated by GC‐FID and GC/MS analyses. In total, 54 of the 57 detected essential‐oil components were identified. Among the different compound classes present in the essential oils, the chief constituents belonged to the monoterpenes, comprising an average content of 79.67% of the total oil composition (74.80% of monoterpene hydrocarbons and 4.87% of oxygenated monoterpenes). Sesquiterpenes were present in smaller amounts (average content of 19.02%), out of which 16.39% were sesquiterpene hydrocarbons and 2.62% oxygenated sesquiterpenes. The most abundant components in the needle essential oils were the monoterpenes δ‐car‐3‐ene, β‐phellandrene, α‐pinene, β‐myrcene, and β‐pinene and the sesquiterpene β‐caryophyllene. From the total data set of 57 detected compounds, 40 were selected for principal‐component analysis (PCA), discriminant analysis (DA), and cluster analysis (CA). The overlap tendency of the four populations suggested by PCA, was as well observed by DA. CA also demonstrated similarity among the populations, which was the highest between Populations I and II.