Search

Black root rot is a dangerous disease affecting many crops. It is caused by pathogens formerly known as Thielaviopsis basicola and then reclassified as two cryptic species, Berkeleyomyces basicola and B. rouxiae. The aim of this study was to perform species identification, morphological characterization, and pathogenicity tests for fungal isolates obtained from tobacco roots with black root rot symptoms in Poland. DNA sequences of the three regions (ITS, ACT, MCM7) were highly similar to the sequences of B. rouxiae deposited in the NCBI database. Phylogenetic analysis confirmed the assignment of the obtained isolates to this species. The cultures of four representative isolates (namely OT2, OT3, WPT7, WPT8) showed a similar structure and gray/brown color of the mycelium, although their growth rate varied from 3.8 to 5.1 mm/day depending on the isolate. The sizes of the endoconidia and chlamydospores showed a considerable variation, although they fit within ranges previously described for B. rouxiae. Pathogenicity tests performed on young tobacco plants grown in the inoculated peat substrate revealed differences among the four isolates. WPT7 demonstrated the lowest level of aggressiveness for tobacco. In contrast, the remaining three isolates caused severe disease symptoms and significantly reduced shoot and root dry weights of the susceptible cultivar Virginia Joyner. A parallel pathogenicity test performed on cultivar VRG 10TL confirmed the effectiveness of black root rot resistance derived from Nicotiana debneyi.

Fungi have the potential to colonize soybean seeds in the field, during their maturation in the pods and after harvest, during storage. The aim of this study was to identify fungi inhabiting soybean seeds after storage with varying germination capacity and to evaluate their chemical composition. The research material consisted of twelve soybean seed lots collected from the fields in southern Poland and stored over winter. The germination percentage of these lots ranged between 20.67% and 81.33%. The seeds were subjected to analyses of the main chemical components and mycological analysis. Fungal isolates were subjected to taxonomic identification using microscopic methods and DNA sequencing (using internal transcribed spacer region and secondary barcoding regions). A total number of 355 fungal isolates from 16 genera were identified, with Aspergillus, Alternaria, and Fusarium being the most common. Species were successfully identified in 94% of isolates. Twelve examined seed lots varied significantly in the number of isolated fungal species (from 1 to 17). Moreover, they also differed in the isolated species composition. Highly significant positive correlation was found between the number of Aspergillus psedudoglaucus isolates and the content of free fatty acids. In turn, the number of Fusarium spp. isolates correlated negatively with protein and nitrogen content. Similarly, highly significant negative correlation was found between the number of all fungal isolates and the 1000-seed weight, indicating that smaller seeds are more vulnerable to fungal infection. The results obtained in this study identify species of fungi which may be responsible for lowering quality of the seeds obtained in southern Poland.

Wound infections became a great challenge, especially after the emergence of bacterial resistance to commonly used antibiotics. Medicinal plants can be the source of alternative antibacterial agents effective against multi drug resistant (MDR) bacteria. This research aimed to evaluate the effectiveness of different Silybum marianum seed extracts in fighting MDR bacteria that infect wounds. First, thirty purified bacterial cultures obtained from superficial, infected wounds were subjected to antibiotic sensitivity tests. The selected MDR isolates were then used to test the antimicrobial effects of different S. marianum seed extracts. The most potent extract was evaluated for its impact on the ultrastructure of the cells of sensitive bacterial isolates using transmission electron microscopy (TEM). The bioactive ingredients of this extract were analyzed by means of gas chromatography–mass spectroscopy (GC–MS). Then, in-silico absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties were predicted for the main components. The results indicated that four out of 30 bacterial isolates were considered MDR bacteria. Primary morphological features of colonies, secondary (automatic) identification using the Biomerieux Vitek 2 System, and 16S rRNA sequencing of the four isolates confirmed that they represent Staphylococcus aureus, Stenotrophomonas maltophilia, Klebsiella pneumoniae, and Escherichia coli. Among different extracts of S. marianum seeds, ethanol extract showed the strongest inhibitory effect on both Gram-positive and Gram-negative bacteria, with minimum inhibitory concentration (MIC) values between 9.375 and 1.172 mg/mL. However, at concentrations four times higher, this extract was unable to kill bacterial cells, indicating that it had a bacteriostatic effect on the tested MDR strains. TEM revealed denaturation and distorted cell ultrastructure in S. aureus and S. maltophilia after exposure to ethanol extract. In addition, GC–MS analysis of the ethanol extract identified nine compounds known to have important biological activities, and ADMET analysis showed good drug-likeness for two of these compounds. Consequently, S. marianum seeds could be a good source of alternative bacteriostatic agents effective against MDR bacterial strains that cause wound infections.

Fungi belonging to the Fusarium genus are commonly isolated from soybean plants and seeds but not all of them are pathogenic. The aim of this study was to compare the pathogenicity among different Fusarium isolates obtained from soybean plants with disease symptoms originating from an experimental field located in the southeast of Poland. Nineteen fungal isolates were selected for the pathogenicity assay, including eight isolates of F. oxysporum, six isolates of F. graminearum, four isolates of F. culmorum and one isolate of F. redolens. Species identification of these isolates was carried out using microscopic methods and sequencing of two genes: translation elongation factor 1-alpha (TEF1) and RNA polymerase second largest subunit (RPB2). To our knowledge, this is the first report of F. redolens being isolated from soybean in Europe. The pathogenicity test was set up by fungal inoculation of healthy soybean seeds of three cultivars: Abelina, Atlanta and Mavka. Symptoms were assessed seven days after inoculation. Disease area percentage of Fusarium inoculated seeds was significantly higher compared to uninoculated control. Nineteen isolates differed in their aggressiveness as the median disease area percentage ranged between 5.0 and 88.0% depending on isolate. The obtained isolates of four Fusarium species may be used in the future screening of soybean cultivars for resistance to these pathogens.

Soybean [Glycine max (L.) Merrill] plants are potential hosts for different pathogens. Soil-borne diseases, caused by pathogenic fungi, are considered to be the main reason for the loss of soybean yields worldwide. The aim of the research was to isolate fungi inhabiting underground parts of soybean in order to identify potential pathogens present in south-east Poland. Research material comprised of seven soybean cultivars grown in field in 2017-2019. Samples collected in three subsequent vegetative seasons constituted soybean plants with disease symptoms on cotyledons, stems and roots. Fragments of the infected plant tissues were subjected to mycological analysis. A total of 1692 pure fungal isolates were obtained from the sampled plants and almost 80% of these isolates were assigned to Fusarium genus. Among Fusarium spp. isolates, the most frequently detected species was F. oxysporum (71.3%). Other detected Fusarium species included: F. graminearum, F. culmorum, F. avenaceum, F. poae, F. solani (syn. Neocosmospora solani), F. sporotrichioides and F. fujikuroi. Other fungi accounted for approx. 19% of the obtained isolates and their main representatives were: Alternaria alternata, Trichoderma sp., Rhizoctonia solani, Mucor sp., Cladosporium sp. and Rhizopus sp. Comparison of these results with published data from other regions of Poland shows differences in prevalence of different species of soil-borne fungi.

Weeds may contribute to the spread of plant virus epidemics by acting as reservoirs of viruses or/and their vectors. The aim of this research was to study the prevalence of five viral pathogens in weeds in the fields of solanaceous crops in six provinces in Poland differing with soil and climate conditions. Most of the sampled sites were associated with tobacco production. The total number of 157 samples of tobacco and 600 samples of weeds were subjected to DAS-ELISA detection of tomato spotted wilt orthotospovirus (TSWV), cucumber mosaic virus (CMV), potato virus Y (PVY), tobacco mosaic virus (TMV) and tobacco ringspot virus (TRSV). Twenty nine percent of samples of weeds were infected with at least one virus. TSWV and TMV were the most frequently detected in 17.5% and 14.7% of samples, respectively. In most provinces where infected tobacco was found, the same virus was also detected in weeds. Results of this survey are discussed in the context of the current status of virus epidemics in tobacco fields in Poland.