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Genetic diversity pattern in Populus Nigra populations of two major river systems in Turkey

Çiftçi, Asiy
European black poplar (Populus nigra L.) is an important tree species in terms of social, economic and ecological interest in Turkey. Although, poplar plantations in large areas meet the needs of the economy, the natural genetic resources of the species have been highly degraded due to anthropogenic effects and natural biological events. To assess genetic diversity structure of natural populations, 124 naturally distributed European black poplar trees from two major rivers (Kızılırmak and Göksu) in Turkey were sampled and screened using 20 nuclear microsatellite DNA loci. To detect the possibility of natural hybridization, 10 reference Populus deltoides L. trees were also studied with six microsatellite loci. The results from hybrid detection analysis indicated that the majority of individuals from two river systems was found as pure European black poplar. Four trees in Göksu and one tree in Kızılırmak river populations were determined as F2 hybrids according to with high probability calculations with diagnostic and informative alleles. A reduced level of expected genetic diversity (Mean He= 0.55) and the excess of heterozygosity (Mean Ho= 0.80) were detected in the studied populations. The results suggested that all populations experienced a recent bottleneck event which reduced allelic diversity caused to excess of heterozygosity. Kızılırmak river populations were not differentiated significantly from Göksu river population (FST = 0.06). There was little differentiation among four populations of Kızılrımak river (FST = 0.03) due to high level of vegetative material vi (polen, seed and branches) circulation within the river system. Human impact, biological events such as, bottleneck and natural hybridization events caused the eroded genetic diversity and extensive genetic material circulation from P.deltoides polluted local genetic resources. To prevent further genetic degradation and to protect genetic resources of the species, efficient conservation and breeding strategies should be implemented as soon as possible. This study provides the necessary genetic information to develop such strategies.