In our research, the induction of organogenesis and the regeneration of the sweet potato
plants took place on the same medium, with no passage. The primary explants of
‘Carmen Rubin’ began to develop organs after 4 days, while the ‘White Triumph’ ones
– about 3 days later. In most cases, shoots and roots developed simultaneously. Within
four weeks, all the primary explants grew into plants consisting of one or two shoots,
the explant and roots (fig. 1C). It was observed that numerous explants of both cultivars
began to develop a number of shoots, but only one of these shoots achieved a larger
(normal) size, while the rest usually remained in the form of buds – structures smaller
than 0.5 cm, and some reached a length of 2–3 cm. The percentage of plants with
2 shoots depended on the cultivar and the composition of the medium (tab. 1). On the
medium contained kinetin and gibberellin, 2 shoots were developed by 13.3% of ‘Carmen
Rubin’ plants and 15.7% of ‘White Triumph’ plants, while on the medium with
auxin – by 16.7% of ‘Carmen Rubin’ plants and 55.5% of ‘White Triumph’ plants.
Plants produced three or more shoots were not observed. The average weight of ‘Carmen
Rubin’ plants was significantly larger than that of the ‘White Triumph’ ones (tab. 1).
The weight of the plants regenerated on the medium containing 0.1 mg dm-3 KIN and
1 mg dm-3 GA3 was larger than that of these regenerated on the medium with
0.5 mg dm-3 IAA. The explants retained the green colour, while some of them produced
small amounts of dense green callus (about 7%). There were no significant differences
in the weight of explants between the two cultivars. The dominant shoots of ‘Carmen
Rubin’ were characterized by longer stems, while the number of nodes was similar in
both cultivars. The root systems usually consisted of one long root and several shorter
ones. Two roots of similar length or a single long root were observed very rarely. On
average, ‘Carmen Rubin’ plants had more roots than the ‘White Triumph’ ones. There
was no difference in the length of the dominant root between the two cultivars. The
plants grown on the cytokinin and gibberellin medium had more roots and longer stems
than these regenerated on the auxin medium. The hormonal composition of the media
had no effect on the number of nodes (tab. 1).
The number of explants obtained from sterile plants was similar to the number of
nodes (tab. 1). The secondary explants were much smaller then the primary ones
(fig. 1A). The average weights of secondary and primary explants depended on the
cultivars (‘Carmen Rubin’: 22,5 and 153.1 mg, ‘White Triumph’: 21,2 and 146.5 mg,
respectively).
In the second experiment, the onset of the development of shoots and roots
(5% explants) was observed after 10 days in the ‘Carmen Rubin’ plants and 4 days later