Results and Discussion
Cultures showed signiicant growth for both experiments.
However, we are summarizing the results for STS-133 only because
results for STS-135 were similar. Growth was observed as
a signiicant percentage increase in area for the in vitro cultures
(Fig. 3). Best results were observed for MS1 with the formation
of pre-embryogenic masses and subsequent shoot formation,
while MS2 produced mostly callus. No contamination was
observed. Genotype and explant type had a direct effect on the
growth of cultures. Jatropha in vitro cultures from Brazil and
India accessions had greater growth (percent area increase) than
cultures from Mexico in both space and ground (Fig. 4). Stem
explants showed greater growth as compared to cotyledon and
leaf explants. Differences in in vitro cell growth for jatropha were
previously reported in preliminary pre-light studies (Vendrame
and Pinares, 2013).
Stem explants provided the greatest growth for both space and
ground environments (Fig. 4). In contrast, in preliminary studies,
stem and cotyledon explants provided the greatest growth of in
vitro jatropha cell cultures (Vendrame and Pinares, 2013). No
signiicant differences were observed in growth for all accessions
when using leaf explants in both space and ground (Fig. 4).
When comparing growth between space and ground samples,
no signiicant differences were observed, except for a greater
growth for cotyledon explants of Brazil accession cultures in
the ground (Fig. 4).
The effects of genotype and explant type for in vitro growth
of cultures in a space environment provides some valuable information
that can be applied for the selection of plant material
that is more suitable for space experiments in the future. It also
provides some germplasm diversity for potential induction of
genetic changes. Genetic variability in jatropha can assist in
jatropha breeding and genetic improvement programs (Bhering
et al., 2013).
Plant regeneration from in vitro cultures is affected by the
type of cells formed, resulting in the need for evaluating different
explant types and their vitro growth. While all explants showed
some undifferentiated type of growth (callus), subsequent shoot
initiation occurred (Fig.5A) with shoot formation observed (Fig.
5B) from cotyledon and leaf explants. For stem explants, structures
similar to pre-embryogenic masses (PEMs) were observed (Fig.
5C), which differentiate into somatic embryos. Somatic embryogenesis
is a desirable in vitro culture system for jatropha, as it