Cercospora leaf spot (CLS) caused by the fungus Cercospora beticola is the most common and destructive disease of sugar beet in Poland. Strobilurin (Quinone outside inhibitors—QoI) fungicides are widely used for CLS control. In Poland for several years, a gradual increase in QoI tolerance has been observed. In 2015, most of the tested isolates (56%) collected from several independent locations were able to grow in a PDA medium supplemented with 1 µg/ml of azoxystrobin. An additional test showed that the EC₅₀ value for the most resistant isolates was ≥100 µg/ml, while for the sensitive ones it was ≤0.01 µg/ml. The results of cytochrome b partial DNA sequencing revealed that all resistant isolates contained single guanine to cytosine substitution (G/C), predicting the conversion of glycine to alanine at the 143 codon position (G143A). To our knowledge, this is the first report in a peer-reviewed paper on G143A mutation determining the strobilurin resistance of C. beticola in Poland.

The plants have developed several defense mechanisms to counteract pathogens. Among others, it includes activation of antioxidant enzymes likeβ-glucosidase and guaiacol peroxidase (GPX). These proteins participate in the oxidation of phenolic compounds, contributing to their increased fungitoxicity. The study aimed to analyze changes in the activity ofβ-glucosidase and GPX in four genotypes of winter oilseed rape (Mendel, Monolit, Polka, line L1425) inoculated with seven isolates:Alternaria brassicicola,Alternaria brassicae,Alternaria alternata(3 strains),Ulocladium chartarum(syn.A. chartarum), andCladosporium cladosporioides. We noted that the varieties of oilseed rape, tested fungal species, and time of the plant material collection had significant (P < 0.001) effect on the activity ofβ-glucosidase and GPX per protein and fresh matter content comparing to the control group.A. brassicicolacaused the highest mean increase inβ-glucosidase and GPX activity in all examined genotypes, while other pathogens had a lower impact. Significantly lowerβ-glucosidase activity inoculated by various pathogens was noted between the L 1425 line and other varieties. GPX activity was in the opposite, the lowest activity was recorded in the Mendel variety, and the highest in the L 1425 line.

High-throughput sequencing (HTS) has revolutionized phytopathology by overcoming many limitations of traditional diagnostic methods, as it permits precise pathogen monitoring, identification, and control, with ribosomal DNA (rDNA) regions serving as reliable markers for fungal classification. In this study, next-generation sequencing (NGS) was used, targeting the ITS1 and ITS2 regions to explore fungal diversity and pathogen presence in winter wheat grain samples and identifying 183 OTU sequences across 115 taxa. The ITS1 analysis yielded 249,743 reads, with Fusarium sp. (61%) as the dominant pathogenic taxon, followed by Sporobolomyces sp. (14%), Cladosporium sp. (3%), and other yeast-like or saprotrophic fungi, such as Cryptoccocus spp., F. wieringae, and B. alba. Sequencing of ITS1 also permitted the detection of F. acuminatum and the quarantine-regulated pathogens T. caries and T. triticoides. The ITS2 analysis produced 179,675 reads, with F. culmorum (47%) as the most abundant taxon, confirming significant grain contamination with this pathogen. Other frequently detected taxa included yeast-like fungi such as C. tephrensis (21%) and V. victoriae (13%), along with saprotrophic species like S. roseus and Davidella sp. ITS2 provided better resolution for the identification of Fusarium species by the detection of more pathogenic taxa associated with cereal diseases, including F. culmorum, as well as F. cerealis, F. poae, and F. tricinctum. The analysis revealed a diverse fungal community, including other pathogens such as A. porri, B. cinerea, and C. herbarum, as well as various non-pathogenic and saprotrophic fungal taxa. These findings underscore the complementary utility of ITS1 and ITS2 in profiling fungal diversity and detecting critical pathogens using HTS, highlighting the potential of these DNA regions for monitoring and managing cereal crop health.