Using trace elements in otoliths to discriminate between wild and farmed European sea bass (<Emphasis Type="Italic">Dicentrarchus labrax</Emphasis> L.) and Gilthead sea bream (<Emphasis Type="Italic">Sparus aurata</Emphasis> L.)

Trace elements in otoliths of sea bass (Dicentrarchus labrax L.) and sea bream (Sparus aurata L.) from fish farms and coastal wild populations in the western Mediterranean Sea were analysed by inductively coupled plasma-mass spectrometry. Results showed that concentrations of Mg, K, and Mn differed significantly between wild and farmed sea bass, while concentrations of Mg, K, Mn, Fe, Zn, Sr, and Ba varied significantly between wild and farmed sea bream. Discriminate analysis and cross-validation classification showed that the trace element profile in otoliths can be used to separate farmed fish from wild stocks with high accuracy on both sea bass (individuals correctly classified: 90.7 %) and sea bream (individuals correctly classified: 96.6 %). Moreover, trace elements in otoliths resulted to be useful to discriminate among wild fish stocks within each species.     

First report of invasive brown marmorated stink bug Halyomorpha halys (Stål, 1855) in Croatia

The brown marmorated stink bug, Halyomorpha halys (Stål, 1855) (Hemiptera: Heteroptera: Pentatomidae), has been spreading over Europe since the first documented records from Liechtenstein in 2004 and Switzerland in 2007. It is considered to be a pest in many agricultural crops and a household nuisance. In 2017 the species was observed in Croatia for the first time, in the city of Rijeka on the north Adriatic coast. Halyomorpha halys has already been recorded in three nearby countries (Italy, Hungary and Serbia), and therefore the arrival of this species had been expected from neighbouring populations or from distant sources via trading goods. To identify the pathway of entry, the haplotypes of H. halys (Stål, 1855) individuals were analysed by comparing a part of the mitochondrial COI gene with other haplotypes present in the GenBank database. Individual specimens shared the most common haplotype with nearby Italian and Hungarian populations.     

Viruses affecting tomato crops in Serbia

In a two-year survey (2011–2012), 3220 samples were collected and analyzed in order to determine the presence and distribution of viruses in tomato crops at 56 localities of 18 districts in Serbia. Out of 12 viruses tested, Cucumber mosaic virus (CMV), Potato virus Y (PVY), Alfalfa mosaic virus (AMV), Tomato spotted wilt virus (TSWV), Tomato mosaic virus (ToMV) and Tobacco mosaic virus (TMV) were detected in 42.1, 40, 11, 8.6, 2.3 and 1.3% of the total tested samples, respectively. The results revealed that CMV was prevalent in 2011 and PVY in 2012. CMV and PVY, apart from being predominant, were also the most widespread viruses. In general, single infections were the most frequent type of infection. Additionally, the most common mixed infections were double infections and the most prevalent combination was CMV and PVY. In 2011, the incidence of diseases and the percentage of all infection types were significantly higher than in 2012. Furthermore, in 2011, regardless of total single infections being prevalent compared to mixed infections, two prevailing viruses were commonly detected in mixed infections. The additional molecular testing of ELISA-negative samples using virus specific primers did not reveal the presence of Pepino mosaic virus (PepMV), Tomato yellow leaf curl virus (TYLC), Tomato infections chlorosis virus (TICV) and Tomato chlorosis virus (ToCV).     

Biochemical and physiological responses to long‐term Citrus tristeza virus infection in Mexican lime plants

Reactions that occur when a plant is subjected to Citrus tristeza virus (CTV) infection often result in triggering of numerous defence mechanisms to fight the infection. The reactions vary according to virus strain, host genotype, time of exposure to the infection and environmental conditions. To date, no study has examined in detail the consequences of 10‐year exposure to CTV infection on the biochemical and physiological status of susceptible Mexican lime plants (Citrus aurantifolia). To understand the reaction of such plants, changes in nutrient status, total proteins, enzyme activity involved in scavenging of reactive oxygen species, photosynthetic and transpiration rates, chlorophyll content, membrane permeability and water content were analysed in plants infected with different CTV isolates and in healthy plants. The activity of superoxide dismutase and polyphenol oxidase significantly decreased in the infected leaves, and membrane permeability was lower in the infected plants. Macro‐ and micronutrient elements were significantly changed: concentrations of leaf nitrogen, zinc, magnesium and iron were elevated but potassium concentration depressed in comparison to noninfected control leaves. Levels of other analysed nutrient elements, enzymes, photosynthesis and stomatal conductance, chlorophyll content and relative water content were unchanged. Clear physiological changes were found among infected and noninfected control plants but none between plants infected with different CTV isolates. The data suggest that some of the defence mechanisms investigated here were suppressed due to the continuous and long‐term pressure of biotic stress.     

Biostimulation as a process aiding tebuconazole degradation in soil

Purpose

The purpose of this study was to compare effects of two biostimulating substances (compost and bird droppings) on the proliferation of microorganisms, enzymatic activity, and resistance of spring barley in soil exposed to tebuconazole fungicide. Both biostimulating substances were also assessed for their efficacy in tebuconazole degradation in soil.

Materials and methods

A pot vegetation experiment was performed with soil belonging to the Eutric Cambisols to test the effect of tebuconazole on the biological activity of soil. Its adverse effect on the biological properties of soil was minimized through the use of biostimulating substances (compost and bird droppings), the effect of which was expressed with the IF_C/BD index. The RCh index was used to determine the effect of tebuconazole on the proliferation of soil microorganisms and enzymes, the BA₂₁ index was used to express soil fertility based on the activity of soil enzymes, whereas the RS index—to express the resistance of spring barley to the administered doses of tebuconazole. Finally, analyses were conducted to determine the efficacy of soil amendment with biostimulating substances in tebuconazole degradation.

Results and discussion

Study results demonstrate that tebuconazole caused significant changes in the proliferation of the tested groups of microorganisms, in the activity of soil enzymes, and in spring barley yield. It was especially noticeable in pots in which the soil was exposed to its highest dose, i.e., 2.499 mg kg^?1. Soil supplementation with bird droppings had a positive effect on the development of soil microorganisms and on the enzymatic activity in the soil. In turn, compost addition to soil exerted various effects on the biological properties of soil. Both biostimulating substances failed to improve spring barley yield. Tebuconazole degradation was more intense in the soil fertilized with bird droppings than with compost.

Conclusions

Results of this study suggest that tebuconazole can affect the stability and health status of soil ecosystems by modifying their biological properties. The high sensitivity of soil microorganisms and enzymes to stress conditions makes them reliable environmental bioindicators. The strive for eliminating the adverse impact of fungicides on soil microbiome through the use of appropriate remediation methods, like, e.g., biostimulation, is of greater concern from the ecological perspective.

     

Species selection maintains self-incompatibility

Identifying traits that affect rates of speciation and extinction and, hence, explain differences in species diversity among clades is a major goal of evolutionary biology. Detecting such traits is especially difficult when they undergo frequent transitions between states. Self-incompatibility, the ability of hermaphrodites to enforce outcrossing, is frequently lost in flowering plants, enabling self-fertilization. We show, however, that in the nightshade plant family (Solanaceae), species with functional self-incompatibility diversify at a significantly higher rate than those without it. The apparent short-term advantages of potentially self-fertilizing individuals are therefore offset by strong species selection, which favors obligate outcrossing.