Post-transcriptional gene silencing (PTGS), or RNA silencing, is one of the key mechanisms of antiviral defence used by plants. To counter this defence response, viruses produce suppressor proteins that are able to inhibit the PTGS pathway or to interfere with some of its function. The aim of this study was to evaluate the RNA silencing suppressor (RSS) activity of P0 proteins from selected European isolates of the beet-infecting poleroviruses beet chlorosis virus (BChV) and beet mild yellowing virus (BMYV) using two different experimental systems: (i) agro-infiltration of Nicotiana benthamiana green fluorescent protein-positive plants and (ii) mechanical inoculation of Chenopodium quinoa using a beet necrotic yellow vein virus (BNYVV, genus Benyvirus) RNA3-based replicon. The results demonstrated that P0 of most BMYV isolates exhibited RSS activity, although at various efficiencies among isolates. Conversely, P0 of BChV isolates displayed no RSS activity in either of the two systems under the experimental conditions used. These results are the first reported evidence that P0 proteins of two closely related beet poleroviruses show strain-specific differences in their effects on RNA silencing.

Helichrysum italicum (Roth) G. Don. is one of the most important cosmetic and medicinal plants originating from the Mediterranean region of Europe. The aim of this study was to assess the chemical profile as well as antioxidant and antibacterial potential of the species cultivated in the temperate climate of Central Europe. The analyses were carried out using herbs and inflorescences. The content of essential oil ranged from 0.25 g × 100 g−1 in the herb to 0.31 g × 100 g−1 in the inflorescences. Neryl acetate, accompanied by α-pinene in the herb (10.42%), and nerol in inflorescences (15.73%) were the dominants here. Rutoside, as well as rosmarinic, chlorogenic, neochlorogenic, isochlorogenic b and cichoric acids, were detected in both raw materials using HPLC-DAD. Within this group, cichoric acid was the dominant (2647.90 mg × 100 g−1 in the herb, 1381.06 mg × 100 g−1 in the inflorescences). The herb appeared to be more abundant in phenolics in comparison with the inflorescences. When given antioxidant activity (determined using DPPH and ABTS assays), both methanolic extract and essential oil obtained from the herb indicated higher potential than those originating from the inflorescences (74.72, 61.38 and 63.81, 58.59% in the case of DPPH, respectively). In turn, regarding antimicrobial activity, the essential oil from inflorescences was distinguished by stronger bacteriostatic power than the herb essential oil. Gram-positive bacteria were more sensitive to both essential oils in comparison with Gram-negative ones, with S. aureus ATCC 25923 as the most susceptible (MIC 1; MBC 16 mg × mL−1) among tested strains.

Key message Comprehensive management of urban greenery is a key approach to control fungal diseases of trees and shrubs to avoid the deterioration in their health status. Abstract Preliminary investigations on the health status related to fungal diseases of trees and shrubs growing in four green squares in Warsaw were conducted in 2017–2019. The examined plants were affected by diseases that are commonly identified in urban greenery, e.g., powdery mildew (causal agents: Sawadaea tulasnei, S. bicornis, Podosphaera leucotricha, Podosphaera sp., Erysiphe alphitoides, E. magnifica, E. berberidis, E. flexuosa and E. adunca), rusts (Gymnosporangium sabinae, Melampsora laricis-populina), apple scab (Venturia inaequalis), tar spot of maple (Rhytisma acerinum), and oyster mushroom (Pleurotus ostreatus). The causal agents of the diseases were identified based on their morphological (macro- and microscopic) features. Preventing and managing fungal plant diseases and reduction of their effects are the key tasks in conscious management of urban greenery. To address this issue, the study presents basic guidelines based on the application of various recommended actions and good practices, which constitute a comprehensive and sustainable strategy for integrated protection of trees and shrubs against these diseases. The implementation of the strategy for complex management of urban greenery is a crucial measure aimed at maintenance of a high health status of urban plants.

Different field isolates of the 'beet poleroviruses' Beet mild yellowing virus (BMYV) and Beet chlorosis virus (BChV) (genus Polerovirus, family Luteoviridae) collected in France and Poland were evaluated for transmissibility from and to sugar beet plants by different aphid species. In general, both BMYV and BChV were efficiently transmitted by Myzus persicae and by a French clone of Macrosiphum euphorbiae. In contrast, transmissibility of the two poleroviruses by an English clone of M. euphorbiae was evidently weaker, although the aphid samples contained the virus as demonstrated by RT-PCR. None of the BMYV or BChV isolates was transmitted by Aphis fabae or Myzus ascalonicus. In attempting to correlate biological properties with molecular variations, the RT proteins were sequenced. Some amino acid point variations, presumably affecting aphid transmissibility, were identified.

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Some histological changes were observed in blueberry stems infected by the fungus G.cassandrae. Dead cells of subepidermal collenchyma and cortical parenchyma filled with brown flocculent deposits were seen in the lesion areas. Pycnidia characteristic for the conidial stage of the fungus (Topospora myrtilli) were found in the collenchyma layer. The diseased tissues were found to be separated from the healthy ones by a layer of cork cells which was initiated under the epidermis and ended under the pericycle. Beneath this cork layer lamellar collenchyma and collenchyma-like phelloderma formed. Similar histopathological changes were observed in blueberry stems infected by seven other fungi