under similar culture conditions for stem explants, S1S5 showed rapid and abundant callus growth and quick
regeneration, while S4S5 showed much sower callus growth and less regeneration. Further, in S1S5 both diploids
and tetraploids were regenerated, whereas in S4S5 only diploids were regenerated.
Hormonal composition of the medium
The quantitative ratios of auxin and cytokinin appear to influence the composition of the proliferating cell
population and to result in polyploidization of cells in both anther and stem cultures.
Anther culture: Among the regenerated plants in the diploid clone, S12S13,
67% were tetraploids. This is
ascribed to the presence of kinetin in the media used for regeneration, in addition to the prolonged culture.
Stem explants: The calli from triploid of L. peruvianum gave regeneration to a high frequency of hexaploids
because of the presence of a higher concentration of kinetin in the medium, in addition to coconut milk used for
regeneration. Similarly, in the diploid clone, S1S5, more tetraploids were regenerated from the medium containing
kinetin.
Some cases were noted, where a combination of the factors, such as genotype, composition of the medium
and/or physiological condition of the donor plants, appears to have influenced the differentiation. For instance, the
hybrid plants grown in Rome gave regeneration on Gand 1 + CM + K (Ancora, this issue of TGC), whereas the
plants grown in Louvain-la-Neuve (Belgium) did not respond to culture on Gand 1 + CM + K, but gave regeneration
on other different media, A7 and A37 (Cappadocia et al., unpubl). Similarly, the cytochimeras of L. peruvianum gave
regeneration on Gand 5, but not on Nitsch's medium containing adenine. However, the hybrid gave regeneration on
a medium containing adenine (A37) (Cappadocia et al. loc. cit.), but not on Gand 5.
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