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A molecular cytogenetic survey of Cucumis sativus L. revealed a chromosomal polymorphism among 2 European pickling cultivars of ‘Borszczagowski’ and ‘Monastyrski’, and one Japanese cultivar of ‘Zibai’ by fluorescent banding method with chromomycin A3 (CMA) and 4′,6-diamidino-2-phenylindole (DAPI), and fluorescence in situ hybridization (FISH) with the probes of 5S, 45S rDNA and telomere repeat sequences. Heterochromatic banding polymorphism was found in some chromosomes with CMA and DAPI staining, whereas no chromosomal polymorphism was found in FISH. Thus, the FISH allowed us to identify all of homologous chromosomes in each cucumber cultivars, while CMA and DAPI banding showed an easy detection of the polymorphism in cucumber chromosomes, even in close related cultivars between European pickling cultivars.

To resolve the discrepancy among previous karyotype descriptions, chromosome comparative study between two closely related cucumber cultivars, C. sativus L. cv. Borszczagowski and cv. Monastyrski, was performed by chromosome preparation technique with enzymatic maceration, and fluorescent banding method with chromomycin A3 (CMA) and 4′,6-diamidino-2-phenylindole (DAPI). Heterochromatic band polymorphisms were detected in chromosomes 2, 3, 5 and 7, whereas no chromosomal polymorphism was found in chromosomes 1, 4 and 6. In cv. Borszczagowski chromosome 2, CMA+DAPI+ heterochromatic band at terminal region of the long arm was smaller than that of cv. Monastyrski. Chromosome 3 of cv. Monastyrski was characterized by CMA+DAPI+ bands on the terminal regions of both arms, whereas that of cv. Borszczagowski displayed only on the terminal region of long arm. Distinct CMA+DAPI+ band located at terminal region of the long arm in cv. Borszczagowski was larger than that of cv. Monastyrski. In chromosome 7, terminal CMA+DAPI+ band at the short arm was only observed in cv. Monastyrski. This result suggested that inconsistency of karyotypes among previous reports was due to chromosomal polymorphism.

Zamia angustifolia, Z. integrifolia, Z. pumila and Z. pygmaea had the common chromosome number of 2n= 16 and the common karyotype which consisted of 12 median-, 2 submedianand 2 subterminal-centromeric chromosomes. The 4 species showed commonly the CMA-positive band in the centromeric region of 2 median-, 2 submedian-and 2 subterminal-centromeric chromosomes. In contrast, Z. furfuracea, Z. loddigesii, Z. skinneri and Z. vazquezii had commonly the chromosome number of 2n=18 and 10 median-and 2 submedian-centromeric chromosomes in karyotype but exhibited 6 different chromosomes from each other. Zamia furfuracea and Z. loddigesii displayed the CMA-positive band in the centromeric region of 8 median-and 6 acro-centromeric chromosomes. Zamia skinneri performed the CMA-positive band in the centromeric region of 4 acro-and 2 terminal-centromeric chromosomes, while Z. vazquezii performed the CMA-positive band in the centromeric region of 4 median-and 6 terminal-centromeric chromosomes. Zamia muricata had the chromosome number of 2n=23 differed from that of the previous count, the karyotype which consisted of 7 median-and 16 acro-centromeric chromosomes and the CMA-positive band in the centromeric region of 4 median-and 16 acro-centromeric chromosomes. Then, the 9 species of Zamia studied exhibited unclear DAPI-positive bands near the centromeric region of most of their chromosomes. By comparison, the closely related Ceratozamia mexicana had the chromosome number of 2n=16 and the CMA-positive band at the terminal region of 6 chromosomes.