Rosa spp. Extracts as a Factor That Limits the Growth of Staphylococcus spp. Bacteria, a Food Contaminant.

Due to their richness of bioactive substances, rose hips are a valuable raw material for obtaining extracts with potential antimicrobial activity. The aim of the study was to determine the antagonistic potential of whole pseudo-fruit and flesh extracts of three Rosa sp. varieties against Staphylococcus spp. bacteria isolated as food contaminants. The biological material in this study consisted of seven strains of bacteria from the genus Staphylococcus. Two strains-Staphylococcus aureus ATCC 25923 and Staphylococcus epidermidis DSMZ 3270-were used as reference strains. The other five strains were food-derived isolates-S. epidermidis A5, S. xylosus M5, S. haemolyticus M6, S. capitis KR6, and S. warneri KR2A. The material was the pseudo-fruits of Rosa canina, Rosa pomifera Karpatia, and Rosa rugosa. The polyphenols were extracted from the fleshy part and the whole pseudo-fruit for all rose varieties. The tested preparations differed significantly in their polyphenol composition. The sum of polyphenols ranged from 28 862 to 35 358 mg/100 g of lyophilisate. The main groups of polyphenols found in the preparations were flavanols and ellagitannins. All of the tested extracts inhibited the growth of staphylococci at a concentration of 500 mg/mL. Rosa rugosa fruit extract showed the strongest antimicrobial properties among the studied extracts. For all the strains, the growth inhibition had a diameter of 20.3-29.0 mm. Moreover, six out of the seven tested strains showed the highest inhibition with the use of this extract. The MIC of rose extracts was in the range of 3.125-500 mg/mL and was strictly dependent on the bacterial species, the species of the rose, and the part of the fruit from which the extract was obtained. Correlations were assessed between the main groups of polyphenols in the extracts and their inhibition of bacterial growth. In the case of pseudo-fruit extracts, the inhibitory effect on bacterial growth positively correlated with the content of ellagitannins, and this effect was observed for almost all the tested strains. The results presented herein follow the current trend of minimising the use of chemical preservatives in food; from this point of view, rose extracts are very promising.

The Effect of Supplementary LED Lighting on the Morphological and Physiological Traits of Miniature Rosa × Hybrida 'Aga' and the Development of Powdery Mildew (Podosphaera pannosa) under Greenhouse Conditions.

We investigated the growth traits, flower bud formation, photosynthetic performance, and powdery mildew development in miniature Rosa × hybrida 'Aga' plants grown in the greenhouse under different light-emitting diode (LED) light spectra. Fluorescence-based sensors that detect the maximum photochemical efficiency of photosystem II (PS II) as well as chlorophyll and flavonol indices were used in this study. Five different LED light treatments as a supplement to natural sunlight with red (R), blue (B), white (W), RBW+FR (far-red) (high R:FR), and RBW+FR (low R:FR) were used. Control plants were illuminated only by natural sunlight. Plants were grown under different spectra of LED lighting and the same photosynthetic photon flux density (PPFD) (200 µmol m-2 s-1) at a photoperiod of 18 h. Plants grown under both RBW+FR lights were the highest, and had the greatest total shoot length, irrespective of R:FR. These plants also showed the highest maximum quantum yield of PS II (average 0.805) among the light treatments. Red monochromatic light and RBW+FR at high R:FR stimulated flower bud formation. Moreover, plants grown under red LEDs were more resistant to Podosphaera pannosa than those grown under other light treatments. The increased flavonol index in plants exposed to monochromatic blue light, compared to the W and control plants, did not inhibit powdery mildew development.

Apple Autotetraploids with Enhanced Resistance to Apple Scab (Venturia inaequalis) Due to Genome Duplication-Phenotypic and Genetic Evaluation.

Among the fungal diseases of apple trees, serious yield losses are due to an apple scab caused by Venturia inaequalis. Protection against this disease is based mainly on chemical treatments, which are currently very limited. Therefore, it is extremely important to introduce cultivars with reduced susceptibility to this pathogen. One of the important sources of variability for breeding is the process of polyploidization. Newly obtained polyploids may acquire new features, including increased resistance to diseases. In our earlier studies, numerous tetraploids have been obtained for several apple cultivars with 'Free Redstar' tetraploids manifesting enhanced resistance to apple scab. In the present study, tetraploids of 'Free Redstar' were assessed in terms of phenotype and genotype with particular emphasis on the genetic background of their increased resistance to apple scab. Compared to diploid plants, tetraploids (own-rooted plants) were characterized with poor growth, especially during first growing season. They had considerably shorter shoots, fewer branches, smaller stem diameter, and reshaped leaves. In contrast to own-rooted plants, in M9-grafted three-year old trees, no significant differences between diplo- and tetraploids were observed, either in morphological or physiological parameters, with the exceptions of the increased leaf thickness and chlorophyll content recorded in tetraploids. Significant differences between sibling tetraploid clones were recorded, particularly in leaf shape and some physiological parameters. The amplified fragment length polymorphism (AFLP) analysis confirmed genetic polymorphism of tetraploid clones. Methylation-sensitive amplification polymorphism (MSAP) analysis showed that the level of DNA methylation was twice as high in young tetraploid plants as in a diploid donor tree, which may explain the weaker vigour of neotetraploids in the early period of their growth in the juvenile phase. Molecular analysis showed that 'Free Redstar' cultivar and their tetraploids bear six Rvi genes (Rvi5, Rvi6, Rvi8, Rvi11, Rvi14 and Rvi17). Transcriptome analysis confirmed enhanced resistance to apple scab of 'Free Redstar' tetraploids since the expression levels of genes related to resistance were strongly enhanced in tetraploids compared to their diploid counterparts.