PhD

The study entitled "Assessment and induction of variability in Plumbago species
for high plumbagin content" was carried out in the Department of Plant Breeding and
Genetics, College of Horticulture, Vellanikkara during 2005-2009. The main objective of
the study was to induce variability in Plumbago species for high plumbagin content
through -in vitro mutagenesis. A detailed survey was conducted throughout Kerala and
accessions of Plumbago were collected from different ecogeographical regions ranging
from Western Ghats to coastal regions of Kerala. The species Plumbago rosea seemed to
be mainly distributed in highlands and medium altitude especially in the midlands of
Kerala. The passport data of the collected accessions were prepared and indigenous
collection(IC) numbers were obtained from NBPGR, New Delhi. Twenty five accessions
of Plumbago rosea and one accession of Plumbago zeylanica were catalogued.
Twenty six accessions thus collected were evaluated in replicated trial for genetic
variability with respect to their biometrical traits and quality. To know the causes of
failure of seed set in Plumbago rosea floral biology of the two species of Plumbago was
studied . .The data were subjected to statistical analysis and results interpreted. The twenty
six accessions were grouped into seven clusters which showed that there is no parallelism
between the geographical distribution and clustering pattern. The path coefficient
analysis indicated that large sized leaves and increased dry root weight contributed
maximum to plumbagin content. Based on the ranking for dry root weight and plumbagin
content three accessions were subjected to in vitro mutagenesis.
In vitro regeneration through direct organogenesis and indirect organogenesis was
standardised in Plumbago rosea in MS medium. Nodal segments were identified as best
explants showing direct regeneration. The in vitro regenerated plants from nodal cultures
on cultivation produced significantly large tuberous roots with moderate plumbagin
content compared to conventional rooted cuttirigs. The callus derived from leaves,
regenerat~d shoots, and roots. Thus, mass multiplication of Plumbago rosea through
tissue culture was standardised.


In vitro mutagenesis of selected accessions of P. rosea was successfully carried
out. Based on percentage of regeneration, LDso values of 20 Gy and 40 Gy were fixed for
nodal cultures and callus cultures respectively. The hardened plants obtained from
selected accessions through in vitro mutagenesis showed significant variation for leaf
number and size. Based on these characters variants were selected and carried over for
field establishment in pot culture. The tissue culture variants on field establishment
showed wide variability with respect to its stature, plant type and other morphological
traits. Three in vitro mutants having plant type with large leaves and short stature for high
plumbagin content were identified. The plumbagin content of these in vitro mutants have
to be evaluated for its commercial exploitation.