Agrobacterium rhizogenes-mediated transformation of Witloof chicory – In vitro shoot regeneration and induction of flowering

Stable transformation and expression of transgene was
achieved in Witloof chicory (Cichorium intybus L.
cv. Lucknow local) using Agrobacterium rhizogenesmediated
system. Transformation frequencies varied
with use of different types of strains of A. rhizogenes,
concentration of A. rhizogenes and age of explants.
The transfer of rolA gene into chicory genome was
confirmed by PCR analyses. The supplementation of
putrescine at 40 mM level with 2¢-3¢-O-isopropylidene
adenosine (2-iP) (2 mg l–1) and, gibberellic acid (GA3)
(0.5 mg l–1) to MS medium resulted in increased shoot
multiplication and shoot growth in untransformed
plants compared to the transformed plants of C. intybus.
Putrescine at 40 mM level also resulted in flowering in
both the systems on the 28th day, in untransformed
and transformed plants. The supplementation of
AgNO3 at 40 μM level to the untransformed axillary
buds of C. intybus on MS media with 2-iP (2 mg l–1)
and GA3 (0.5 mg l–1) resulted in higher shoot multiplication
(36.9 ± 2.63 shoots per culture) and higher
growth of shoots (7.82 ± 0.76 cm) in comparison
to transformed ones for shoot multiplication (11.6
± 0.89 shoots per culture) and growth of shoots (3.2
± 0.24 cm). Moreover, 40 μM AgNO3 treated cultures
showed in vitro flowering on the 28th day in both the
systems. The information generated in terms of transformation
protocols, in vitro morphogenesis including
flowering will make genetic transformation easier for
chicory crop improvement.