The substrate had a significant effect on the formation of
potato microtuber. Only one microtuber can regenerate from
each cutting. Data fromTable 1show that the highest formation
of rate microtuber (95%) was recorded when explants were
cultivated on solid media. However, higher fresh weight and
diameter of microtuber were obtained in explants cultured on
one-storeyin vitrohydroponic system with filter paper or cotton
layer substrate in comparison with cultivation in solid media.
All the microtubers yielded from thein vitrohydroponic system
were uniform in size and yellow in color. These results clearly
showed that both filter paper and cotton layer may be
successfully used as substrates in one-storeyin vitrohydroponic
systems in order to produce potato microtubers. Furthermore,
our results revealed that the MS medium, which is always used
for conventionalin vitrosolid media, is effective also when it is
used as a liquid medium without agar for the formation of
microtubers inin vitrohydroponic system, where an inorganic
nutrient solution is usually used. The rich nutrient composition
of the MS medium promotes the early development of potato
cutting nodes and the microtuber formation. The microtubers
formed in the one-storeyin vitrohydroponic system are bigger
and weightier (Fig. 3d) due to the fact that they could uptake
and accumulate nutrient components and plant growth
regulators (PGRs) from the carrier substrates, especially from
cotton layer, easier than from the solid media