INTRASPECIFIC VARIATION IN CS-137 ACTIVITY CONCENTRATION IN SPOROCARPS OF SUILLUS-VARIEGATUS IN 7 SWEDISH POPULATIONS

Following the Chernobyl accident in 1986, sporocarps of Suillus varieg atus in Sweden showed a large amount of individual variation in concen tration of Cs-137 activity. Our aim was to determine the degrees to wh ich this variability in sporocarp Cs-137 levels could be explained by differences between (i) local populations, (ii) fungal genets and (iii ) locations within genets. Five populations in a 100-yr-old Scots pine forest, located within a 1 km(2) area, and two populations in Scots p ine/Norway spruce forest, located 40 km northwest of Uppsala, were inv estigated. In total, 154 sporocarps were analysed to determine their C s-137 content. Of these, the genetic affiliations of 86 were successfu lly characterized using somatic incompatibility reactions. Twenty-six genets were found which, on average, consisted of 65 sporocarps. The g enets averaged 7.5 m in size, measured as the length between the most distant sporocarps. The mean sporocarp Cs-137 level was 67.1 +/- 2.8 k Bq kg(-1) D.W. (range between 13.6 and 182). According to analyses of variance, within-population variation accounted for 60% of the total v ariation in Cs-137 levels, while 40% was ascribed to variation among p opulations. Within a population, Cs-137 levels did not generally diffe r significantly between genets. Plausible reasons for intraspecific va riation in radiocaesium content in sporocarps are discussed.