Proceedings of the XLVI Italian
Society of Agricultural Genetics - SIGA Annual Congress
Giardini
Naxos, Italy - 18/21 September, 2002
ISBN 88-900622-3-1
Poster
Abstract - 1.19
MOLECULAR CYTOGENETICS OF VITIS VINIFERA L. AND FICUS
CARICA
L: LOCATION OF rDNA SEQUENCES
FALISTOCCO
E., ANTONIELLI L.
Dipartimento
di Biologia Vegetale e Biotecnologie Agroambientali, Borgo XX Giugno 74, 06121
Perugia, Italy
grapevine,
fig, fluorescent in situ hybridization, ribosomal genes, triploidy
Grapevine (Vitis vinifera L.) and fig (Ficus carica L.) are among the oldest fruit trees
cultivated in the Mediterranean regions. The thousands varieties of grapevine
actually existing derive from the single species V. vinifera which originated in Mid Asia. Compared
to other crops of similar importance, genetic studies in this species began
only recently. Nevertheless, the molecular approach used in the last years has
contributed to a very rapid increase in the knowledge of the grape genome. F.
carica is very
widespread species mainly because of the rusticity and the high capability of
adaptation of its wild form: the caprifig. The species is usually considered
gynodioecious rather than dioecious since it comprises female plants having
only female flowers and plants with separate male and female flowers. These
plants, althought hermaphrodite, are considered functionally male because
produce pollen. Althought the species is very interesting from a biological
point of view, genetic studies are very scanty, paricularly those concerning
chromosomes, a situation common to many tree species of agricultural interest.
The development of molecular cytogenetic techniques, such as in situ hybridization with fluorochromes (FISH),
has given a tremendous impulse to chromosome studies with great benefit of
species which are unsuited to conventional cytological treatments. The physical
mapping of repetitive genes is often the first step to acquire information on
genome structure of species almost unexplored from the cytogenetic point of
view.
In this study the physical location of
18S-5.8S-25S and 5S ribosomal genes on chromosomes of V. vinifera and F. carica was analyzed by using the probes pTa71
and pXVI in double target in situ
hybridization. Ten accessions of grapevine and fifteen of fig were investigated.
The chromosome numbers 2n=38 and 2n=26
were confirmed for V. vinifera
and F. carica,
respectively. One plant of fig resulted to be triploid with 2n=3x=39. The
results of FISH revealed that in the genome of V. vinifera there are two pairs of sites of
18S-5.8S-25S genes presumedly associated to the secondary constrictions. A
certain difference in the intensity of the signals of the hybrid sites was
observed among accessions. Only one pair of loci of 5S genes was instead found.
In all the accessions these loci appeared very small and were difficult to
detect. The distribution of the rDNA sequences in F. carica was similar to that of grapevine with
two pairs and one pair of 18S-5.8S-25S and 5S gene sites respectively. However
in this species the 5S loci have a remarkable size and were always clearly
distinguished. The results of this study is providing information on the
chromosome organization of these species, in order to realize a molecular
karyotype of both V. vinifera
and F. carica.