In the Institute of Plant Protection Branch in Sośnicowice an investigation was performed on establishing novel methods for testing biological activity or seed dressings against snow mould (Microdochium nivale). Seeds of winter wheat used for the experiments in artificial conditions were disinfected in sodium hypochlorite, subsequently infected with the pathogen, and treated with seed dressing fungicides (Baytan Universal 19.5 WS, Zaprawa Funaben T, Maxim 025 FS, Raxil Extra 515 FS and Vitavax 200 FS). In laboratory tests inoculation with conidial suspension was applied, and in climatic chamber experiments either conidial suspension or inoculum grown on sand-cornmeal medium was used. The field experiment with the same seed dressings was carried out on naturally infested plots, and the disease developed under snow cover lasting for 58 days. Two novel climatic chamber methods (Z and PK) proved to be suitable for testing biological activity of seed dressing fungicides against snow mould (M. nivale) as correlation coefficients with field results at P=0.05 were 0.9760 and 0.9453. Method Z was recognised as more suitable. Differences between seed dressings were statistically insignificant. The laboratory method was recognised as useful for controlling the pathogen (M. nivale), but its usefulness for controlling the disease (snow mould) may not be sufficient under a range of different winter conditions.
Winter hardiness of plants is limited mainly due to sensibility to Iow temperature and winter fungus damages. Snow mould is a disease that affects many species of winter cereals, turf and forage grasses. In Poland it is caused mainly by the common and economically important fungal pathogen Microdochium nivale causing pink snow mould, destructive disease of seedlings, stem bases and ears. The aim of the study was to investigate the dynamie of Microdochium nivale infection and cytological changes in cold-hardened Lolium perenne Danish cv. Darius. Plants were inoculated with mycelium. The studied plants demonstrated fast defence response to fungus attack, accumulating phenolics already one day after inoculation, however no infecting hyphae within leaf tissue at this time were detected. The first infection hyphae in plants were observed two days after inoculation. Microscopy observations revealed sheaths of the youngest leaves located in the crowns as the main infection way. These observations showed that Microdochium nivale hyphae uptake nutrients from the host by haustoria damaging the protoplasts of mesophyll cells causing their strong plasmolysis. This type of feeding is characteristic for biotrophic and hemibiotrophic parasites. Our observation proved that Microdochium nivale is a hemibiotrophic pathogen and inoculation with its mycelium is very effective and fast and causes serious damages of Lolium perenne cells.
The aim of the study was to investigate changes in activity of catalase (CAT) and non-specific peroxidase (PX) in leaves of chosen forage grasses during pathogenesis evoked by Microdochium nivale and to state if the activity of these antioxidants could be recognized as the physiological marker of grass resistance to snow mould. Plants of Festuca pratensis cv. Skra, Festuca arundinacea cv. Kord, Festulolium braunii cv. Felopa, Lolium multiflorum cv. Tur, Lolium perenne cvs Darius and Taya were hardened and then inoculated by snow mould caused by Microdochium nivale. The leaf samples were collected prior to infection, and 2, 4 and 8 days after inoculation. Each plant cultivars demonstrated specific activity of catalase and non-specific peroxidase. Skra and Taya recognized as more tolerant to M. nivale showed inhibited CAT activity during pathogenesis, however the infected plants of cv. Skra were characterized by a lower CAT activity than the control during the whole time of experiment, while cv. T aya 4 and 8 days after inoculation. No universal pattern of PX activity for all studied plant species was found. Skra cv. demonstrated the highest PX activity especially 8 days after the infection. Grass resistance to M. nivale may be evaluated on the basis of activity of both catalase and non-specific peroxidase. Plants more resistant to this disease are characte-rized by inhibited activity of catalase and activation of cell wall peroxidases.
Among winter grain crop diseases, snow mould is one of the most serious diseases, causing considerable yield losses. In 2002–2009, harmfulness of snow mould in winter triticale and efficiency of seed dressing products in controlling the disease were studied. Yielding of winter triticale for different degrees of infection by snow mould was determined. The result of performed studies revealed that yield losses ranged from 7.3 to 42.4% depending on the degree of infection. The calculated relative coefficient of disease harmfulness was 0.77±0.12%, and the harmfulness threshold for snow mould – 27.7±8.0%. Fungicides Maxim SC and Kinto Duo FC showed the best results in controlling snow mould and preventing plant death.
Effect of shade, nutrition, height of mowing and density of turf on snow mould (Microdochium nivale) prevalence on Lolium pereme under turf maintenance were studied in 2000-2004 at Radzików (central Poland). The materials for studies were cultivars of L. perenne originated from Poland and abroad. The turf experiments were performed in three series of trials where each factor were analysed independently. The cultivars were assessed for: density of turf, the first symptom of disease and snow mould injury in spring. The investigations revealed that shade as well as high nutrition applied in autumn and high mowing of grass influenced significantly snow mould prevalence on L. perenne. The cultivars expressed a wide range of susceptibility to snow mould. The cultivars with high density of turf were the most injured by snow mould. Disease occurred at different periods of autumn and winter, usually before snow fall. Winter weather conditions had a slight effect on changes in snow mould injury of L. perenne in subsequent years.
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