The diversity of plant-associated bacteria is vast and can be determined by 16S rRNA gene metabarcoding. Fewer of them have plant-beneficial properties. To harness their benefits for plants, we must isolate them. This study aimed to check whether 16S rRNA gene metabarcoding has predictive power in identifying the majority of known bacteria with plant-beneficial traits that can be isolated from the sugar beet (Beta vulgaris L.) microbiome. Rhizosphere and phyllosphere samples collected during one season at different stages of plant development were analyzed. Bacteria were isolated on rich unselective media and plant-based media enriched with sugar beet leaves or rhizosphere extracts. The isolates were identified by sequencing the 16S rRNA gene and tested in vitro for their plant-beneficial properties (stimulation of germination; exopolysaccharide, siderophore, and HCN production; phosphate solubilization; and activity against sugar beet pathogens). The highest number of co-occurring beneficial traits was eight, found in isolates of five species: Acinetobacter calcoaceticus, Bacillus australimaris, B. pumilus, Enterobacter ludwiigi, and Pantoea ananatis. These species were not detected by metabarcoding and have not previously been described as plant-beneficial inhabitants of sugar beets. Thus, our findings point out the necessity of a culture-dependent microbiome analysis and advocate for low-nutrient plant-based media for high-yield isolation of plant-beneficial taxa with multiple beneficial traits. A culture-dependent and -independent approach is required for community diversity assessment. Still, isolation on plant-based media is the best approach to select isolates for potential use as biofertilizers and biopesticides in sugar beet cultivation.

This study explores the functional traits of Pseudomonas spp. isolated from rhizospheric soils and their potential as plant growth-promoting rhizobacteria (PGPR). Four isolates were selected and characterized based on morphological, physiological, and biochemical parameters. The results demonstrated their tolerance to various abiotic stresses, resistance to heavy metals and pesticides, and ability to produce plant-beneficial compounds, including siderophores, hydrogen cyanide, and indole-3-acetic acid. Although certain PGPR traits were absent, the overall profile indicates the potential utility of these isolates in sustainable agriculture and stress-prone environments.

The experiment evaluated fruit weight and the content of primary metabolites (soluble solids, total sugars, invert sugars, total acids, pH, and sucrose) in berry fruits (raspberry, blackberry, strawberry, blueberry, and black currant). During the experimental period, significant differences in the tested parameters were observed among species. The highest fruit weight was recorded in the strawberry, whereas the lowest values were found in the blackberry and black currant. Soluble solids ranged from 8.24 (blackberry) to 15.1% (black currant). A high content of total and invert sugars was determined in blueberry, whereas black currant exhibited a high level of total acids. Strawberry and blueberry samples had the highest pH values, indicating lower acidity, while the lowest pH was measured in black currant, reflecting its higher acid content. The sucrose content in the berries varied among species, ranging from 0.26 to 0.82%. Principal component analysis (PCA) analysis showed the correlation among species and identified group patterns based on multiple fruit quality traits. Pearson’s correlation coefficient revealed a significant correlation between fruit weight and primary metabolites. The present results indicate that berry fruits are rich in primary metabolites and can be used in primary agricultural production, as well as in the pharmaceutical and food industries.

Using beneficial bacteria from the plant microbiome to combat pathogens is an environmentally friendly strategy for biological control. Although significant progress has been made in characterizing microorganisms with biocontrol potential, the optimal methods for applying such biological preparations to achieve maximum effectiveness against plant pathogens remain insufficiently defined. Our goal was to select rhizobacteria from the sugar beet microbiome and analyze their biocontrol capacity in both indirect and direct applications to protect the plant from Pseudomonas syringae pv. aptata P21. The methodological approach differed: indirect application involved seed priming with selected strains, Bacillus safensis MRh275, B. pseudomycoides JRh226, Stenotrophomonas maltophilia JRh266, or the T2 consortium (MRh275 and JRh266), while direct application involved simultaneous treatment of both the pathogen and the biocontrol strain. Although the direct approach resulted in a greater reduction in lesions and a lower concentration of H₂O₂, the indirect approach showed higher activity of peroxidase and superoxide dismutase as antioxidant enzymes, as well as phenylalanine ammonia-lyase, which is involved in the phenylpropanoid pathway and plant defense mechanisms. Infected plants showed higher expression of NPR1, MYC2, and LOX defense-related genes only under indirect biocontrol with all three strains, except in the T2 application. The T2 consortium performed best in direct biocontrol, where it most effectively reduced lesions. Since encounters between plants and pathogens cannot be accurately predicted, and the application of biological preparations should be easy and accessible for farmers, this study highlights the use of indirect biocontrol through seed priming to enhance the plant’s intrinsic defense capacity.