Chronic radiation exposure modifies temporal dynamics of cytogenetic but not reproductive indicators in Scots pine populations

Genetic polymorphism of Plantago major populations from the radioactive and chemical polluted areas

The variability of nine microsatellite loci was studied for Plantago major L. populations from radioactive (East-Ural Radioactive Trace, EURT) and chemical (Karabash Copper Smelter, KCS) contaminated areas (Urals, Russia). The absorbed dose rates in the EURT area were 178-1455 times higher than background, and the indices of the total toxic load in the KCS area were 13-42 times higher than background values. In total, 65 alleles were identified in P. major populations, while the number of alleles per locus in the EURT and KCS samples was lower than in the background samples. The expected heterozygosity in all loci significantly exceeded the observed, indicating a high level of inbreeding. The largest number of rare alleles (11-21) was found in background samples, of which 3-7 alleles were private. In the technogenically disturbed zones, 8-11 rare alleles (1-2 private) were noted. The Bayesian analysis (K = 3) showed that no unique groups were found in any of the areas; descendants of all founders (pioneers) were represented in each population, but in different proportions. However, only 4.1% of the variability was distributed between local P. major populations (F_ST = 0.041) and 95.9% was concentrated within the samples. A pairwise comparison revealed genetic differentiation between all EURT samples. In the KCS area, there was no significant differentiation in pairs of samples that were at a distance of 3-4 km from each other. For samples from the KCS and background sites, the Mantel test showed a statistically significant relationship between geographical and genetic distances, therefore, the intensity of migration flows between these areas is high. For samples from the EURT and background areas, no such dependence was found. In both impact zones, P. major populations showed reduced genetic diversity. This article discusses the causes of this phenomenon.

Scots pine as a promising indicator organism for biomonitoring of the polluted environment: A case study on chronically irradiated populations

In this paper the main results of long-term (2003-2016) observations on Scots pine populations inhabiting sites affected by the Chernobyl accident are presented. Populations growing for many years under chronic radiation exposure are characterized by the enhanced mutation rates, increased genetic diversity, changes in the gene expression and in the level of genome-wide methylation, alterations in the temporal dynamics of cytogenetic abnormalities and genetic structure of populations. However, significant changes at the genetic level had no effects on enzymatic activity, morphological abnormalities, and reproductive ability of pine trees. The results presented increase our understanding of the long-term effects of chronic radiation exposure on plant populations in the wild nature and provide important information for the management and monitoring of radioactively contaminated territories.