Genetic variation in two heavily polluted stands of Norway spruce (Picea abies [L.] Karst.) as indicated by nuclear and organelle DNA markers

In two polluted neighbouring stands of Norway spruce, "tolerant" and "sensitive" adult trees were selected in pairs and genotyped by recently developed codominant EST markers as well as by chloroplast microsatellites. The results were compared with data previously obtained from isoenzyme gene markers. Larger allelic multiplicities are indicated in the two sensitive subsets as compared to the tolerant ones, i.e. a mean surplus of 11.5% at 6 EST loci and of 27.2 at 19 isoenzyme gene loci. Frequency distributions of genetic types deviate considerably between tolerant and sensitive subsets but statistical significance is indicated by only one of the EST loci tested. Another EST locus is the only one to reveal statistically significant deviations between the observed heterozygosities of the tolerant and the corresponding sensitive subset of the most heavily polluted stand (38% vs. 15%). Based on allelic distances, both categories of nuclear markers reveal a cluster of three subsets in contrast to one and the same sensitive subset which is part of the most heavily polluted stand. A different cluster is indicated by chloroplast markers: the two sensitive and the two tolerant subsets, respectively, reveal greater allelic similarities than the sensitive and tolerant subsets of each stand. Generally, the applied molecular markers appear to be more indicative for the genetic response of Norway spruce to the given environmental stress than isoenzyme gene markers. Different pollution intensities at the two locations are assumed to account for the observed deviations in the genetic response of the two stands.