Studies On Chromosome Behavior In Three Pinaceous Genera

Pinaceae is the largest family of gymnosperms and the most widespread trees throughout the Northern Hemisphere. It is also the significant material in studies on plant evolution and speciation.Karyotypes of the pinaceous species are unusually conservative, with little differentiation among species except Pseudotsuga menziesii and Pseudolarix amabilis. Almost all the chromosomes of the pinaceous species are metacentric or submetacentric, making it difficult to be distinguished merely by comparing the mitotic chromosome features. Analyses of meiotic behavior will provide with constitutional information between homologous chromosomes or genomes.In our studies, meiotic behavior, such as meiotic index, average paring configurations and frequency of meiotic aberrance, was investigated using microsporocytes (pollen mother cells, PMCs) in three genera of the Pinaceae, including eleven species, a variety and an interspecific hybrid (F₁) in Pinus, three species in Picea, and one specie in Cedrus. Furthermore, using FISH method, nrDNAs were localized on bivalents of the F₁ hybrid in order to find the chromosomal differentiation between the parental species of the interspecific hybrid.I. homologous arm paring configurations and comparison on meiotic behaviorThere is little difference in frequency of chiasma, average configuration, meiotic index and frequency of meiotic aberrance among most species in the Pinaceae. It is difficult to analyze meiotic behavior of different species comparatively. In our studies, we compared the frequency of ring bivalents, rod bivalents, univalents and multivalent among the species involved using the homologous arm paring configuration, which was firstly used in meiotic behavior as a parameter. The index...