Sterilisation procedure with DICA proved to be better
for all three genotypes. In the case of first genotype sterilised
with DICA, 38.2% of uninfected plants were obtained. The
sterilisation of the second genotype was less successful and
only 24.7% explants survived the sterilisation with DICA,
whereas the percentage of non vital explants was the highest,
reaching 49.5%. We can conclude that the concentration of
DICA was too high, or time of treatment was too long for
this genotype. The most successful sterilisation was obtained
in the third genotype, where 86.9% uninfected and vital
explants were obtained. The percentage of contaminated and
non vital explants was much higher after the sterilisation
with sodium-hypochlorite for all three genotypes (Table 1).
Results show that successful induction of in vitro culture
dependents not only on sterilisation method used but it is
also very specific for each genotype. Valles (1987) sterilised
explants of 12 different rose genotypes and the number of
infected plants depended strongly on the genotype used.
In his study, the percentage of infected plants appeared in
range from 2.5 to 58.3%. The occurred infections of plant
material after chemical sterilisation can be caused by internal
infections (micro-organisms present inside the plant itself),
which can be reduced with the use of appropriate antibiotics.
Other reasons for later occurrence of infections could be
inaccurate work (non-sterile forceps or scalpels; working
surface not sterilised with 96 % alcohol; not sufficiently
sterilised nutrient media; etc.) (Pierik 1998). It is well known,
that the growth and proliferation of roses depend strongly on
cultivar (Kane 2000). Horn et al. (1988) reported that nodal
explants showed better results than shoot tips and that the
subcultured shoots with long internodes were more suitable
than subcultures from compact shoots with short internodes
(in means of growth, number, length and fresh weight of
newly obtained shoots).