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(Hs) representing the higher part of total diversity
(Ht) (60% for B. incana, 62% for B. rupestris and
58% for B. villosa). The coefficient of genic differen-
tiation (Gst) is comprised between 0.30 and 0.37.
These mean values were comparable with those re-
ported by Lanner-Herrera et al. (1996) for B. oleracea
populations which ranged between 0.11 and 0.50 and
with those reported by Lazaro and Aguinagalde
(1998a) for B. rupestris group (0.11–0.31). In the
Sicilian taxa the Gst values show high variability for
each polymorphic locus varying from 0.03–0.06 to
0.70–0.79. High values as 0.72 (Pgm-2 ), 0.56 (6Pgd-
1 ) in B. rupestris, 0.52 (Pgm-2 ), 0.49 (Aco-4 ), 0.47
(Aco-2 ) in B. villosa, 0.79 (Lap-1 ), 0.70 (Pgm-2 ) in
B. incana, show that these loci play an important role
of differentiation among the populations.
Concerning the genetic distances, B. incana popu-
lations (in the same group) show a clear separation
from the villoso-rupestris populations. B. mac-
rocarpa, too, forming a separate clade, is very dif-
ferentiated from the other Sicilian species. This evi-
dence is confirmed by RAPD analyses (Geraci et al.
2001) because in these taxa specific genomic zones
were found. Also Lazaro and Aguinagalde (1998a,
1998b) realized by isozymes and molecular markers,
found B. incana more strictly related to B. montana-
B. oleracea group even if taxonomically it belongs to
B. rupestris group (Go´mez-Campo 1980, 1999). B.
villosa and B. rupestris populations, showing distance
values very heterogenous, are not separated as well as
by morphological characters and under geographical
and ecological data (Raimondo et al. 1991). It shows
the close relationship between these species that
partly overlap and then can hybridize. However, also
Lanner-Herrera et al. (1996) studying North-Euro-
pean wild populations relatives of B. oleracea, ob-
served that with isozyme analysis populations of the
same country were not always related.
In conclusion, isozyme analysis was very useful to
characterize Brassica sect. Brassica populations as
regards allelic structure and variability within-popula-
tion.
Enzymatic study was very interesting to assess the
genetic structure of the populations. In fact, genetic
variation within a taxon could be critical for the long
term survival and continuous evolution of a popula-
tion or a species (Huenneke 1991). Population genetic
theory predicts that a decrease of heterozygosity will
lead to reduced individual fitness and population
viability and that a decrease in allelic diversity will
limit the ability of a species to track changing selec-
145
tion (Gemmill 1998). Thus, a knowledge of the levels
and distribution of genetic diversity of threatened or
endangered species is an important element in arrang-
ing conservation programs.
These genetic data have a great importance in
leading conservation actions for these species, rela-
tives to kale crops, that are in some case endangered
or threatened and to provide information necessary for
maximization of genetic diversity which is an im-
portant consideration at the intraspecific and specific
level (Loo et al. 1999). Concerning conservation
methods, Gillies et al. (1997) suggested that in situ
conservation strategies should seek to conserve popu-
lations that show interpopulational genetic variation,
to prevent the loss of genetic diversity within a taxon.
On the other hand, ex situ conservation measures
should include the collection of germplasm from
separated populations with significant genetic differ-
ences (Mart´ın et al. 1997). Our observations suggest
that is necessary to preserve in situ the populations as
dynamic conservation. That should be accompanied
by the threat prevention and by periodic monitoring
(ecologically, genetically) of the status of these popu-
lations. On the other hand these data could be very
useful in ex situ conservation programmes in order to
quantify and to document the diversity that can be
present in a collection and at the same time to use
these information to allow to maximize per accession
of genetic diversity (Lamboy et al. 1994). In this case,
considering that the level of diversity inter- and intra-
populational were comparable could be useful to
conserve a large sample of a large number of popula-
tions as well as a large number of individuals within
each population. Moreover populations showing ex-
clusive alleles deserve particular attention as well as
those made up by few individuals that are threatened
in their natural habitat.
Acknowledgements
The authors are grateful to Prof. C. Go´mez-Campo for
the interesting discussions and to Prof. M. Gustafsson
for the revision of the manuscript and the helpful
suggestions.
References
Arus P. and Orton T.J. 1983. Isozyme and linkage relationships of
isozyme loci in Brassica oleracea. J. Hered. 74: 405–412.