In this work we addressed the main limiting step of DH
production in eggplant through microspore culture: the
regeneration of entire DH plants from microspore-derived
calli. After testing several media previously proposed in the
literature to regenerate eggplant plantlets from explants of
different origins, the results presented hereby clearly point
to the use of M1 (Miyoshi 1996) to obtain the highest rate
of shoot-producing organogenic calli. However, this
medium alone is not sufficient to promote shoot growth.
According to our results, we propose the repeated subculture
(approximately on a monthly basis) of the microsporederived
calli in M1, and then the repeated subculture of the
excised shoots in basal MS medium (M11) to promote the
development of new normal-appearing organs and the
rooting of shoots, and therefore the formation of entire
plantlets. As shown in Table 1, this procedure allowed us
to obtain 7.6 plants every 100 cultivated calli, which represents
a remarkable improvement (*49) compared with
the 2 % obtained in the only previous reference of entire
plant regeneration from eggplant microspore-derived calli
(Miyoshi 1996). We also showed that media supplemented
with GA3, and in particular M13, produced more elongated
shoots, ready for rooting, than any other media. However,
the inability of this medium to promote root growth, and
the increased time and expenses associated to the use of an
additional step with M13, make us to discourage its use.
Finally, we obtained a high frequency of DH individuals
(69.3 %), which is also higher than those previously reported
for eggplant DHs coming from both anther and
microspore culture. To increase this frequency, the genome
of the 5.7 % haploids might be duplicated with colchicine
or oryzalin (Dhooghe et al. 2011). However, *70 % of
DHs seems a percentage good enough for most breeding
programs, and makes us propose to discard the addition of
a step for genome doubling of the haploid individuals,
which can just be disposed of.