Biological control of fungal diseases in a forest nursery : impact on the fungal community, species abundance and some fungal pathogens

Abstract: There is a large production of regeneration material in Sweden, where modernization and new technologies have made it possible to produce a large number of high-quality seedlings. To provide the whole forestry sector with seedlings for regeneration, forest nurseries must as well make sure that the management generate healthy seedlings. Fungal diseases have for a long time been a constant problem for nurseries, but kept under control using chemical fungicides. As chemicals are gradually reduced in the Swedish forestry sector, new methods of disease management must be found and tested. The environment in forest nurseries are suitable for many pathogens, and controlling and changing the climate to disfavor them seems like an impossible task, not economically feasible. However, pathogens like Botrytis sp., Phoma. sp. and Sydowia sp. must be controlled in some way, where one alternative to chemical fungicides are biological control agents. In this study, the four biological control products Binab, Serenade, Prestop and Mikroferm are tested in a forest nursery with pine seedlings. A negative control, which included seedlings sprayed with water, was included in the study. DNA from needles as well as the growth substrate, was extracted and by using sequencing of the ITS2 region it was possible to identify the presence of fungi on seedlings. Phoma sp. was the most commonly identified fungal species among all samples (12 % of all sequences) and Botrytis cinerea and Sydowia polyspora were among the five most common species in needle samples. The fungal community composition differed a lot between needle and peat samples. However, when the fungal community composition of the samples belonging to each treatment were compared, there were no significant differences shown. The fungal community composition changed during time, and significant differences of the fungal community composition was shown when data from four different timepoints were compared. In conclusion: the biological control products did not have a significant effect on the fungal community structure, or certain pathogens studied. Stronger were the effects of time, where certain fungal species increase and decrease during time. In general, the management in connection to this trial generated healthy seedlings.