Molecular Genetic Features of Polyploidization and Aneuploidization Reveal Unique Patterns for Genome Duplication in Diploid Malus

Polyploidization results in genome duplication and is an important step in evolution and speciation. The Malus genome confirmed that this genus was derived through auto-polyploidization, yet the genetic and meiotic mechanisms for polyploidization, particularly for aneuploidization, are unclear in this genus or other woody perennials. In fact the contribution of aneuploidization remains poorly understood throughout Plantae. We add to this knowledge by characterization of eupolyploidization and aneuploidization in 27,542 F1 seedlings from seven diploid Malus populations using cytology and microsatellite markers. We provide the first evidence that aneuploidy exceeds eupolyploidy in the diploid crosses, suggesting aneuploidization is a leading cause of genome duplication. Gametes from diploid Malus had a unique combinational pattern; ova preserved euploidy exclusively, while spermatozoa presented both euploidy and aneuploidy. All non-reduced gametes were genetically heterozygous, indicating first-division restitution was the exclusive mode for Malus eupolyploidization and aneuploidization. Chromosome segregation pattern among aneuploids was non-uniform, however, certain chromosomes were associated for aneuploidization. This study is the first to provide molecular evidence for the contribution of heterozygous non-reduced gametes to fitness in polyploids and aneuploids. Aneuploidization can increase, while eupolyploidization may decrease genetic diversity in their newly established populations. Auto-triploidization is important for speciation in the extant Malus. The features of Malus polyploidization confer genetic stability and diversity, and present heterozygosity, heterosis and adaptability for evolutionary selection. A protocol using co-dominant markers was proposed for accelerating apple triploid breeding program. A path was postulated for evolution of numerically odd basic chromosomes. The model for Malus derivation was considerably revised. Impacts of aneuploidization on speciation and evolution, and potential applications of aneuploids and polyploids in breeding and genetics for other species were evaluated in depth. This study greatly improves our understanding of evolution, speciation, and adaptation of the Malus genus, and provides strategies to exploit polyploidization in other species

Changes of genetic structure between parental and offspring populations in a seed stand of Scots pine [Pinus sylvestris L.]

Eight isozyme gene loci were used to compare genetic structure and variation of parental and offspring populations of Scots pine (Pinus sylvestris L.) in the seed tree stand located in the Woziwoda Forest District of the Tuchola Forest. Although, the estimated parameters indicate small reduction of heterozygosity in offspring populations, the stand may be considered as a valuable seed source for reforestation

Geographic patterns of genetic diversity of Pinus mugo (Pinaceae) in Central European mountains

The genetic diversity within and among twelve populations (379 individuals) of Pinus mugo from the Giant Mts., Carpathians and Alps was analyzed using ten chloroplast microsatellite markers. A stepwise mutation model (SMM) for microsatellite loci was used in order to estimate divergence between populations and provenances from three mountain ranges. High levels of genetic diversity and significant differentiation were found among the three population groups. The populations from Giant Mts., Carpathians and Alps were strongly differentiated between each other, while differences among populations within these massifs were much lower. The pattern of genetic structure observedin dwarf mountain pine can be characteristic in conifers with a disjunctive geographic distribution. The significant genetic structuring among isolated parts of the geographic range of the species may be a result of an ancient fragmentation andlong lasting geographic isolation between the Giant Mts., Alpine and Tatra populations of P. mugo