The Darker the Better: Identification of Chemotype Profile in Soroses of Local and Introduced Mulberry Varieties with Respect to the Colour Type.

Mulberries are the "essence of the past", the so-called Proust effect, for the inhabitants of the sericultural regions who enthusiastically remember feeding silkworms with mulberry leaves and picking the different coloured fruits that were their favourite sweets in childhood. To determine the chemistry behind the colour and taste of mulberry soroses, the main metabolites of the local and introduced varieties were studied. The soroses were classified into five different colour types and the size parameters were determined. The main sugars identified were glucose and fructose, while the predominant organic acids were citric and malic acids, which were highest in the darker varieties, and fumaric and tartaric acids, which were highest in the lighter varieties. A total of 42 phenolic compounds were identified. The predominant phenolic acid was chlorogenic acid, followed by other caffeoylquinic acids and coumaroylquinic acids. The predominant anthocyanins were cyanidin-3-glucoside and cyanidin-3-rutinoside. According to PCA analysis, the colour types showed a clear chemotype character. The sweet taste of the yellowish-white soroses was defined by 49% fructose, followed by 45% glucose and 6% organic acids. The sour character of the black genotypes was characterised by a lower sugar and higher (11%) organic acid content. The colour- and species-dependent effect was observed in the proportion of caffeoylquinic acids and quercetin glycosides, which decreased with increasing colour intensity from 60% of the total to 7%, and from 17% to 1%, respectively. An upward trend was observed for flavanols (5% to 29%) and anthocyanins, which accounted for 62% of the total phenolics in black varieties. This article gives an insight into the metabolite composition of mulberry soroses as the sweets of choice between light and sweet and dark and sour.

The Role of Ascorbate-Glutathione System and Volatiles Emitted by Insect-Damaged Lettuce Roots as Navigation Signals for Insect and Slug Parasitic Nematodes.

The effect of wireworm-damaged lettuce roots on the antioxidative defense system (ascorbate-glutathione cycle, photosynthetic pigments) and movement of insect/slug parasitic nematodes towards determined root exudates was studied in a glasshouse experiment. Lettuce seedlings were grown in a substrate soil in the absence/presence of wireworms (Elateridae). The ascorbate-glutathione system and photosynthetic pigments were analyzed by HPLC, while volatile organic compounds (VOC) emitted by lettuce roots were investigated by GC-MS. Herbivore-induced root compounds, namely 2,4-nonadienal, glutathione, and ascorbic acid, were selected for a chemotaxis assay with nematodes Steinernema feltiae, S. carpocapsae, Heterorhabditis bacteriophora, Phasmarhabditis papillosa, and Oscheius myriophilus. Root pests had a negative effect on the content of photosynthetic pigments in the leaves of infested plants, indicating that they reacted to the presence of reactive oxygen species (ROS). Using lettuce as a model plant, we recognized the ascorbate-glutathione system as a redox hub in defense response against wireworms and analyzed its role in root-exudate-mediated chemotaxis of nematodes. Infected plants also demonstrated increased levels of volatile 2,4-nonadienal. Entomopathogenic nematodes (EPNs, S. feltiae, S. carpocapsae, and H. bacteriophora) proved to be more mobile than parasitic nematodes O. myriophilus and P. papillosa towards chemotaxis compounds. Among them, 2,4-nonadienal repelled all tested nematodes. Most exudates that are involved in belowground tritrophic interactions remain unknown, but an increasing effort is being made in this field of research. Understanding more of these complex interactions would not only allow a better understanding of the rhizosphere but could also offer ecologically sound alternatives in the pest management of agricultural systems.

The Effect of Feeding with Central European Local Mulberry Genotypes on the Development and Health Status of Silkworms and Quality Parameters of Raw Silk.

Silkworm rearing activities ceased in the 1970's in several European countries. Attempts on the re-establishment of ecological and sustainable sericulture in Slovenia and Hungary are ongoing. The aim of the study was to assess the usability of locally adapted mulberry genotypes for sericulture and to estimate connections between leaf compound and silkworm performance parameters. A controlled feeding experiment of silkworms was performed to test the influence of leaves from selected trees on the growth of larvae, the health and microbiological status of larvae (e.g., gut bacterial microbiome, Bombyx mori nucleopolyhedrovirus infection), weight of cocoons and raw silk parameters. The Slovenian and Hungarian mulberry genotypes had significantly higher total protein contents, and lower total phenolic contents and differed significantly in some individual phenolics compared to the reference sericultural and fruit varieties. Significant differences were found in the contents of the macro- and microelements, namely S, Mn, Fe, and Sr. Based on correlative statistics and multivariate analysis, a combined positive influence of proteins, specific phenolics, and microelements on larval growth and silk thread parameters was predicted. The results of the study indicate that selected local Slovenian and Hungarian mulberry varieties are suitable for high-quality silk cocoon and raw silk production.

Response of Berula erecta to Lead in Combination with Selenium.

Tissue culture of Berula erecta is suitable cultivation system for research purposes connected with contamination and phytoremediation studies. In previous investigation we determined the optimal dose concentration at which Se stimulates plant growth and positively affects the antioxidative status in this experimental system. In current study, we investigate its response to exposure to lead (Pb) and further the possible protective effect of Se(IV) against Pb exposure. Plants were grown in 10 and 50 mg Pb L-1 solution without and with added Se (0.1 mg L-1) for six weeks. Plants possessed a high affinity to uptake Pb and Se in roots. Addition of Pb inhibited roots elongations and the plant height. In contrast, the combined effect of Se + Pb treatment was reflected in increased weight of plants when compared to Pb treatment alone. Pb decreased the amount of chlorophylls and consequently photochemical efficiency was lowered, whereas in Pb + Se treatment the photochemical efficiency was higher. Furthermore, Pb treatment caused a gradual increase in glutathione in both roots and shoots, however, to a greater percentage in shoots when compared to controls. Exposure to both Pb and Se did not cause any significant changes in root's glutathione level when compared to Pb treatment alone. In shoots, the combined treatment lowered the glutathione significantly, but the levels remained 50% above those of untreated control samples, reflecting that this might be related with the antioxidative effects of Se treatment.

A temporal analysis of antioxidative defense responses in the phloem of Picea abies after attack by Ips typographus.

The temporal gradation of antioxidants was investigated on the phloem tissue of Norway spruce [Picea abies (L.) Karst.] in response to weather conditions and colonization levels of Ips typographus L. (Col., Scolytidae). Two weeks after pheromone dispensers were placed on trees, the initial reaction of Norway spruce to bark beetle attack resulted in moderately lowered levels of total glutathione (tGSH) and total cysteine. Likewise, the total ascorbic acid dropped slightly below the control levels, whereas the concentration of dehydroascorbic acid increased in comparison to the first sampling date. This transient degradation and oxidation of the glutathione and ascorbate system was accompanied by moderately increased concentrations of total phenolics. One month later, the shift in antioxidant balance after moderate attack differed quantitatively from the reaction after massive attack. An intensification of antioxidant defense occurred within moderately affected bark. Total cysteine and tGSH contents were markedly raised, whereas the concentrations of total ascorbic acid and total phenolics were slightly increased by moderate attack. On the other hand, massive bark beetle colonization caused a strong decrease in tGSH and total phenolics, whereas total cysteine and total ascorbic acid values remained at control level. Dependent upon the intensity and the success of the attack, a progressive degradation of antioxidants was determined at later sampling dates, which was accompanied by an obvious oxidation of the ascorbate and glutathione pools. With an unsuccessful defense upon massive attack, the thiols and total phenolics did not reach a new steady state, but deteriorated until the end of the brood beetles' development. In contrast, the dynamic antioxidative response within the moderately affected trees indicated an acclimation stage in the middle of July. It was characterized by a higher accumulation of tGSH, total ascorbic acid and total phenolics as well as a more reduced redox state of glutathione. A sequence of changes in the endogenous levels of antioxidant defense molecules in the bark beetle-affected Norway spruce showed consistency with the general ecophysiological stress-response concept, and provided important avenues for evaluating the role and effectiveness of antioxidants in systemic acquired resistance against the complex interactive effects of bark beetle attack and environmental factors.