THESIS

some degree from each other and these deviations may stabilize in long-term cultures
(Hawtin et al., 1997). This process indicates that new forms continually develop and
are stabilized under new constant conditions. Diversification within the Solanum spp.
is a continuing process in which new types develop from continually modified
Solanum genotypes under different environmental conditions at different geographical
locations (Hawtin et al., 1997).
With respect to the identification and classification of genebank accessions,
markers promise to be very effective tools for achieving these purposes. Dehmer and
Hammer (2004), indicated by the information on provenance in geographically,
separated subclusters in S. americanum and partially in S. villosum, clues on the
currently unknown origin of accessions from the genebank seem feasible by AFLP
data.
Therefore, the availability of information on the taxonomic status and the
geographic origin of genebank accessions is a vital prerequisite for both the
conservation and effective utilization of plant genetic resources, yet it is often lacking
for Solanum (Spooner et al. 1992; Waycott and Ford 1994).
4. Interspecific hybridization
Interspecific hybridization plays an important role for transferring the
desirable traits from one species to another, increasing genetic variation, producing
new alloploid species, clarifying the taxonomic relationship by testing several
interspecific combinations, investigating natural selection and speciation process,
being a prominent tool for theoretical and empirical studies in evolutionary biology,
and recently being used to construct genetic linkage map (Briggs and Knowles, 1967).
Harton and de Wet (1971) provided a useful practical approach to classify
crop species and their wild relatives using the concepts of primary, secondary and
tertiary genepools. The primary genepool comprise those species which cross freely
with the crop; the secondary are those species which difficult crossing with the crop
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