Enzymatic activity of potential fungal plant pathogens and the effect of their culture filtrates on seed germination and seedling growth of garden cress (Lepidium sativum L.)

The in vitro ability to produce enzymes and the toxicological influence of culture filtrates from potential fungal plant pathogens on seed germination, sprout growth, stabilization of cell membranes (electrical conductivity of exudates), and growth of seedlings of garden cress (Lepidium sativum L.) were investigated. The fungi used in the study showed significantly different ability to secrete enzymes with different activities. The highest amylolytic activity was shown by Fusarium oxysporum (Fo2), proteolytic activity by F. sulphureum (Fs1564), Gibberella avenacea (Ga2) and G. intricans (Gi2), cellulitic activity by Haematonectria haematococca (Hh776), and pectinolytic activity by strains Fo1 and Fo2 of F. oxysporum. All the fungal filtrates significantly reduced percentages of seed germination, the growth of sprout and seedlings, and destabilization of cell membranes in seedlings. Fusarium poae (Fp2) and G. fujikuroi (Gf1) most strongly reduced seed germination and sprout growth, whereas G. fujikuroi (Gf1) most strongly affected growth and destabilization of cell membranes in seedlings. Fungal enzyme abilities, and in particular pectinase synthesis, do not determine the impact of their culture filtrates on seeds and seedlings. Probably other secondary metabolites synthesized by F. poae (Fp2) and G. fujikuroi (Gf1) have a negative influence on seeds and seedlings of garden cress. The plant used in this study is very sensitive to external factors. Therefore, in the near future, different model plants e.g., cereals, which are less sensitive to external factors, will be used for in-depth characterization of the toxicological influence of culture filtrates from Fusarium spp. and Gibberella spp. on plants.