Abstract
Black locust (Robinia pseudoacacia L.) was introduced in Poland over 200 years ago, and its distribution area now covers the whole country, with the highest concentration of occurrence in the western part. Breeding of this species has been started in Poland for about 20 years, albeit on a limited scale, and two selected seed stands, 34 plus trees and two seed orchards have been registered. So far, selection efforts have not been coupled with the recognition of variation in the genetic structure of local populations. To fill the knowledge gap on genetic diversity, we selected the seven qualitatively best populations of R. pseudoacacia for our study. To clarify the origin of the Polish population of R. pseudoacacia, a sample from a seed stand in eastern Germany and from a seed orchard with Hungarian clones from the Oborniki Śląskie Forest District was added. In this study, three microsatellites were used to evaluate genotypes: Rops15, Rops16 and Rops18, with the Rops15 locus (motif AG) showing hypermutability. Moderate or high variability was observed in all microsatellite loci examined, with a total of 27 alleles identified. In all stands, the average observed number of alleles per locus was higher than the average effective number of alleles per locus. Three main clusters have been identified in the genetic structure of the population, one of which is represented by the population from the Regional Directorate of State Forests in Zielona Góra. The second group comprised the populations from Mieszkowice, the populations Pińczów and Wołów, and the population from Germany. The last one included population from Strzelce and Oborniki Śląskie, where the population from Hungary is represented. This may be of great importance for practice. Perhaps it is worth postulating the separation of two seed regions. Under most scenarios, climate change is projected to change the distribution of forest types and tree species in all biomes. It can be assumed that the importance of black locust in times of climate change is likely to increase.