Abstract
Information on chromosomes is essential for the progress of genetic and biotechnological studies. In this paper, recent progress on studies of chromosome observation in deciduous fruit trees is reviewed. (1) An enzymatic maceration method, preparing good chromosome samples from plants with small chromosomes, was developed for Prunus, Pyrus, Malus, and Diospyros. (2) Some morphologically similar chromosomes could be distinguished by means of the banding technique using fluorochrome staining in Prunus and Pyrus. In addition, the divergence of chromosome configuration seems to be very low or non-existent in view of fluorescent banding patterns in both genera. (3) The number and location of 5S and 18S-5.8S-25S rDNA sites were detected by fluorescent in situ hybridization (FISH) in Prunus, Pyrus, Malus, and Diospyros. The sites of retrotransposons were also visualized by FISH in Pyrus. These results provided fundamental information on the chromosomes. Chromosomal location of the S (self-incompatibility) locus in Malus was also revealed by FISH. In Diospyros, the results of FISH as well as genomic in situ hybridization (GISH) offered new findings on the phylogenetic relationships in this genus and chromosome composition of somatic hybrids.
