ISOLATION OF DAMPING-OFF FUNGI IN NATURALLY REGENERATING PINUS SYLVESTRIS FORESTS OF NORTHERN SCOTLAND. W BODLES l, S WOODWARD l and C LEIFERT 2 l Department of Forestry, University of Aberdeen, MacRobert Building, 581 King Street, Aberdeen AB24 5UA, Scotland, UK; 2 Department of Plant and Soil Science, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 5UD, Scotland, UK Background and objectives Damping-off diseases are common and serious problems in forest nurseries and naturally regenerating forests throughout the world. In Finnish forestry nurseries uni- and binucleate Rhizoctonia and unidentified oomycetes were identified as the main pathogens causing damping-off [1]. Surveys of diseased roots in Norwegian and Finnish forest nurseries and subsequent pathogenicity trials have shown that the most serious attacks occur when Rhizoctonia spp. and Pythium spp. are found together in a complex [2]. Because of the potential impact of these damping-off diseases on the natural regeneration of native forests, the main objective of this study was to identify the pathogenic fungi involved in the decline of the fine root system in naturally regenerating Scots pine (Pinus sylvestris) forests in Scotland. Materials and methods The study was conducted at the following native Pinus sylvestris woodlands in Scotland where natural regeneration is occurring :- Glen Dye, Culbin Sands, Balmoral Estate, Glen Strathfarrar National Nature Reserve (NNR), Beinn Eighe National Nature Reserve (NNR). Soil samples were taken from each of the five areas, encompassing the range in conditions to be found within the area: dry areas to wet areas, hill sides and level plains. The fungi were isolated directly from the soil utilising a variety of susceptible baits and by the soil dilution plate method. Once isolated the fungi were transferred to selective media to place them into preliminary categories. Morphological and molecular identification techniques utilising ITS primers were employed to further identify the isolates into Pythiumspp., Phytophthora
  • spp. or Rhizoctoniaspp.. ln vitro pathogenicity trials were set up to identify the primary pathogens among the fungal strains isolated from the soils. Results and conclusions A total of fifty five fungi were isolated using the soil dilution plate method. Highest numbers of isolates were obtained from Culbin sands and Glen Dye with, respectively, 19 and 18 isolates each from 50g of soil. Fewer fungi were isolated from Balmoral (5 isolates), Strathfarrar (7 isolates) and Beinn Eighe (6 isolates). Most of these isolates were identified as Mortierella spp. a fungal genus not previously described as being pathogenic to pine seedlings. The absence of the three types of pathogenic fungi, described by previous research into damping-off diseases in pine, suggests that they are either absent from the soil in these areas or have been suppressed/outgrown by Mortiereiia spp. during the isolation process. Results from pathogenicity tests with Mortierella spp. and trials comparing soil isolation and pine/lupin/cucumber seed/seedling baiting methods for the isolation of primary pathogens will be discussed. References 1. Liija A, 1994. European Journal of Forest Pathology 24, 181-192. 2. Liija A, Liija S, Poteri M and Ziren L, 1992. Scandinavian Journal of Forest Research 7, 547-556.