Wheat is a staple crop and the key source of vegetable protein in human diet. Fungal phytopathogens significantly reduce the yield potential. The most common and harmful wheat pathogens in Ukraine are Fusarium graminearum Schwabe, Fusarium nivale Ces (Microdochium nivalе), Puccinia triticina Erikss. & Henn, Puccinia graminis sp. tritici Erikss. & Henn, Pyrenophora tritici-repentis (Died.) Drechsler, Septoria tritici Rob. et Desm. Selection of resistant genotypes in the breeding programs as well as diagnostics of diseases relies on combination of immunological, microscopic, and biochemical tools. This work aims at assessing the influence of fungal infection on the biochemical protective reactions in commercial wheat varieties, introgressive lines of winter wheat generated through several rounds of crossing of primary lines, landraces, or amphiploids generated using Aegilops tauschii as one parent with modern wheat varieties at the Plant Breeding and Genetics Institute-National Center of Seed and Cultivar Investigation.

Analysis of the varieties demonstrated that Pyrenophora tritici-repentis caused increase of lipid peroxidation, catalase activity and content of reduced glutathione, sugars and flavonoids. The total protein, chlorophyll-a and chlorophyll-b content as well as glutathione peroxidase activity were lower in infected plants. Elevation of lipid peroxidation could trigger protective mechanisms, including higher catalase activity, and accumultion of flavonoids and reduced glutathione. Infection with Fusarium nivale Ces also causes lipid peroxidation accompanied by two folds higher peroxidase activity, whereas activity of superoxide dismutase and catalase was reduced. Infection with Septoria tritici Rob lead to higher hydrogen peroxide content and superoxide dismutase activity. We also examined peroxisome abundance as a proxy of oxidaive stress and found increae of peroxisome abundance in some genotypes in respose to fungal pathogens.

In case of the introgressive lines, response to Fusarium graminearum comprised higher activity of trypsin inhibitors and lectins. The initial level of trypsin inhibitor activity in the control samples depended on the level of resistance only in case of brown rust. Activation of chitinase and β-1,3 glucanase was detected in response to Fusarium graminearum, brown and stem rust. Measurements of lipid peroxidation products and reduced glutathione content as well as activity of antioxidant enzymes and PR-proteins chitinase and β-1,3 glucanase demonstrated that resistance against Puccinia triticina and Puccinia graminis depends on different mechanisms.

In conclusion, biochemical parameters of fungal pathogen response are genotype-specific. Thus, predicting outcome of a specific host-pathogen interaction requires measuring multiple parameters. Generally, infection caused shifting of the redox homeostasis towards accumulation of hydrogen peroxide and lipid peroxidation products that are toxic to many pathogens. Pathogens also had pronounced impact on peroxisome abundance. These data will contribute to developing strategies for identification of wheat varieties with superior resistance to fungal diseases.