Petäistö, R-L., Lilja, A., Ruhanen, H., Rytkönen, A. and Hantula, J. 2012. Effects of Light and Winter Storage Conditions on Norway Spruce Seedlings with Special Emphasis on the Occurrence of Gibberella avenacea. Baltic Forestry 18 (1): 73-82.

Fusarium-like fungi, together with Herpotrichia, were isolated after winter 2006 from Norway spruce seedlings in a nursery. According to ITS nucleotide sequences and morphology, the most common Fusarium-like species was Gibberella avenacea. Complete (i.e., 100%) conidiospore germination was observed in vitro at 0–25 °C, but its rate and germ tube growth was dependent on temperature.In early July, seedlings were moved outdoors to two conditions: shaded or exposed to sunlight. Thereafter, half of the seedlings were inoculated with Gibberella avenacea asexual spores once a month for four months. Following winter storage in the freezer or outdoors, localized necroses were observed on needles of inoculated and control seedlings. The number of needles and growth rate was higher in seedlings exposed to light. In control seedlings, shoot growth rate and needle dry weight percent were higher in plants stored outdoors compared to those over-wintered in the freezer. On the uppermost shoot quarter, needles were less healthy in seedlings stored in the freezer, whereas needles on the lower shoot quarters of seedlings grown in the shade were healthier than those in light. The damage caused by inoculations was not statistically significant.

Cultures of G. avenacea were obtained almost entirely from inoculated seedlings and identified using ITS sequences and species-specific PCR. The number of G. avenacea isolates was highest in seedlings grown under shade and stored in a freezer as well as in seedlings grown under light and stored outdoors. In shade grown and freezer stored seedlings, G. avenacea was isolated most frequently from tops, whereas it was more often detected in the lower quarters of light seedlings stored outdoors.

Key words: Gibberella  avenacea, Fusarium, Picea abies, container seedlings, overwintering, nursery practice, light, reforestation, Fennoscandian forestry, fusariosis, Fusarium head blight.