﻿AbstractTo have an insight into the karyotype variation of eightCucurbitaceaecrops includingCucumissativusLinnaeus, 1753,CucumismeloLinnaeus, 1753,Citrulluslanatus(Thunberg, 1794) Matsumura et
Nakai, 1916,Benincasahispida(Thunberg, 1784) Cogniaux,
1881,MomordicacharantiaLinnaeus, 1753,Luffacylindrica(Linnaeus, 1753) Roemer,
1846,Lagenariasicerariavar.hispida(Thunberg, 1783) Hara, 1948 andCucurbitamoschataDuchesne ex Poiret, 1819,
well morphologically differentiated mitotic metaphase chromosomes were prepared using the
enzymatic maceration and flame-drying method, and the chromosomal distribution of
heterochromatin and 18S-5.8S-26S rRNA genes (45S rDNA) was investigated using sequential
combined PI andDAPI(CPD)
staining and fluorescencein situhybridization (FISH) with 45S
rDNA probe. Detailed karyotypes were established using the dataset of chromosome
measurements, fluorochrome bands and rDNAFISHsignals.
Four karyotype asymmetry indices,CVCI,CVCL, MCAand Stebbins’ category, were measured to
elucidate the karyological relationships among species. All the species studied had
symmetrical karyotypes composed of metacentric and submetacentric or only metacentric
chromosomes, but their karyotype structure can be discriminated by the scatter plot of
MCAvs.CVCL. The karyological relationships among these species revealed
by PCoA based onx, 2n,TCL, MCA,CVCLandCVCIwas basically in
agreement with the phylogenetic relationships revealed by DNA sequences.CPDstaining revealed all
45S rDNA sites in all species, (peri)centromeric GC-rich heterochromatin inC.sativus,C.melo,C.lanatus,M.charantiaandL.cylindrica, terminal GC-rich
heterochromatin inC.sativus.DAPIcounterstaining afterFISHrevealed pericentromericDAPI+heterochromatin inC.moschata. rDNAFISHdetected two 45S loci in five species and five 45S loci in three species. Among these 45S
loci, most were located at the terminals of chromosome arms, and a few in the proximal
regions. InC.sativus, individual chromosomes can
be precisely distinguished by theCPDband and 45S rDNA signal patterns, providing an easy
method for chromosome identification of cucumber. The genome differentiation among these
species was discussed in terms of genome size, heterochromatin, 45S rDNA site, and
karyotype asymmetry based on the data of this study and previous reports.