Soil tillage and crop rotation are considered important tools in wheat leaf disease control; however, the results of investigations are inconsistent. The aim of the present study was to determine the effect of the soil tillage system and cropping sequence on the development of winter wheat leaf diseases in 2012–2017. The disease development was assessed in a two-factor experiment: (a) soil tillage system; and (b) crop rotation. Foliar fungicides were used uniformly in all variants. The results showed that tan spot (caused by Pyrenophora tritici-repentis) dominated in 2012, 2013, and 2016, but the level of Septoria tritici blotch (Zymoseptoria tritici) was essentially lower and exceeded the severity of tan spot only in 2015. The agronomic practice used significantly influenced only the development of tan spot. Reduced soil tillage and continuous wheat sowing substantially increased tan spot severity, especially when both practices were used simultaneously. Short crop rotation (only wheat and oilseed rape) provided sufficient control of tan spot in ploughed fields, whereas in non-ploughed fields, the level of this disease did not decrease. The results could be explained by differences in the pathogens’ life cycle: P. tritici-repentis ascospores in wheat debris is the main source of infection; in contrast, Z. tritici spreads by conidia from living plants.

Winter wheat (Triticum aestivum) is a crop of which production is associated with rather large investments for nitrogen fertilization and disease control. The aim of this study was to estimate the effect of five variants of fungicide application and four levels of N (nitrogen) top-dressing rate on the yield and grain quality of winter wheat. Field trials were carried out in Latvia (56° 31′ N; 23° 42′ E) for four seasons. Grain yield and quality depended significantly on the conditions of the trial year, as three of them were characterized by drought in varying degrees. Although the average four-year grain yield increased significantly in all fungicide application variants, the effect of this factor was different in individual years. The application of fungicides increased the yield significantly in one year, decreased significantly in another year, while it had no significant effect on the yield in remaining two seasons. The enhancement of N top-dressing rate increased the grain yield significantly every year. The interaction between both examined factors was significant; however, the use of higher N rates not always means that also spraying with fungicides has to be more intensive. A clear effect of fungicide application was observed on 1000 grain weight and volume weight, while the effect of N top-dressing rate was observed on the crude protein, wet gluten and starch content, and Zeleny index.

Wheat stem base disease (WSD) is an important disease complex which can be caused by various pathogens with variable life cycles, ecological requirements and sensitivities to fungicides. Agronomic practices are considered important tools to control this disease complex and influence the spectrum of fungal communities in infected wheat stems. The aim of the present study was to determine the impact of crop rotation schemes and soil tillage methods on the development of WSD and to elucidate the spectrum of causal agents of this disease. The development of WSD was assessed in a two-factorial (soil tillage practice and crop rotation) experiment. The incidence of WSD was evaluated at the BBCH growth stages 83–85. Causal agents of WSD and other fungi were identified using molecular methods. The soil tillage method did not influence the development of WSD, but the impact of crop rotation was significant, and the cropping system where oilseed rape, barley and faba beans were included decreased disease levels. Members of the genera Oculimacula and Fusarium were the most prevalent fungi associated with WSD. Moreover, fungi from other taxonomic groups were detected, with Phaeosphaeria spp. being prevalent. An increasing occurrence of Microdochium spp. was also observed. In conclusion, agronomic practices influenced the level of WSD, but no distinct impact on the fungal spectrum was identified. Further investigation is required to clarify the roles that pathogens and fungi from other taxonomic groups play in the fungal–wheat relationship.

Pyrenophora tritici-repentis is a major wheat pathogen in all wheat (Triticum spp.) growing areas worldwide. Up to date, eight P. tritici-repentis races have been described based on chlorosis, necrosis, or both symptoms caused on race differential wheat genotypes: ‘Glenlea’, 6B662, 6B365, and ‘Salamouni’. Symptom development on differential genotypes depends on the interaction of the pathogen’s necrotrophic effectors named Ptr ToxA, Ptr ToxB, and Ptr ToxC with host susceptibility genes. Ptr ToxA is encoded by the single copy gene ToxA and induces necrosis on sensitive wheat cultivars. Ptr ToxB causes chlorosis and is encoded by the multicopy gene ToxB. The Ptr ToxC is the non-proteinaceous, polar, low molecular mass molecule that also induces chlorosis, but up to date, the gene encoding this toxin is unknown. Races producing Ptr ToxA are predominant in the global Ptr population. There are several reports about new putative races of P. tritici-repentis that do not conform with the current race system, so further research is required. This study aims to collect and systematise available information about the virulence and races of P. tritici-repentis.

Pyrenophora tritici-repentis (Ptr), family Pleosporaceae, is a common wheat pathogen in all wheat-growing regions around the globe. It is widely studied in North America, South America, and North Africa, while data about the fungus genetic diversity in Europe is still insufficient. This study aimed to describe the variation of morphological traits and toxin production of strains collected in Latvia and Belarus. Twenty-one isolates from Latvia, and 12 from Belarus were sampled in 2019 for morphological evaluation in culture and necrotrophic effector gene determination by PCR. All isolates were grouped into nine different morphotypes. Five of these morphotypes were unique for isolates from Latvia, one for Belarus, and three morphotypes were occurring in both countries. No association between the host and the pathogen morphotype was observed. ToxA gene was detected in 44% of the analysed isolates. For 52% of the isolates, PCR did not confirm the presence of any known effector genes of Pyrenophora tritici-repentis. ToxB and toxb were found only in one isolate from Latvia. The studies need to be continued to evaluate the diversity of the pathogen depending on the host species.