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(Hs) representing the higher part of total diversity tion (Gemmill 1998). Thus, a knowledge of the levels
(Ht) (60% for B. incana, 62% for B. rupestris and and distribution of genetic diversity of threatened or
58% for B. villosa). The coefficient of genic differen- endangered species is an important element in arrang-

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