Plant biosystematics with the help of cytology and cytogenetics

Abstract

The importance of cytological and cytogenetic information in the investigation of evolutionary history of species, i.e. biosystematics (cytotaxonomy) and cytogeography, is surveyed. The main issues considered are the numbers and morphology of the chromosomes, the distribution and amount of the different types of chromatin in chromosomes, nuclei at interphase stained with classical and molecular cytogenetic methods, e.g. fluorescence in situ hybridization (FISH), genomic in situ hybridization (GISH) and bacterial artificial chromosome (BAC), painting chromosomes, the isolation of large DNA segments using e.g. pulse-field gel electrophoresis, and chromosome disposition in the cell nucleus. A wide ranging biosystematic interest puts emphasis with the help of cytological and cytogenetic methods on getting to know chromosome variation within the family, genus and species connected with the phenomena of hybridization and polyploidization. Chromosome variation among taxa includes differences in the morphology and numbers of chromosomes, the amount of DNA, the sizes of chromosomes, inner chromosome structure, and DNA sequence, often shown in chromosome bands or various proportions of AT and GC pairs. On this basis we can track the course of evolution among taxa and determine reciprocal relationships. One of the main aims of our work, apart from getting to know evolutionary processes, is to create a taxonomic system of organisms.