PhD

The present study "Induction and evaluation of genetic variability
in Chethikoduveli (Plumbago rosea L.) was undertaken in the Department
of Plant Breeding and Genetics, College of Agriculture, Vellayani during
1995-1998. The study was undertaken through the conduct of two
experiments. (i) Germplasm collection and evaluation (ii) induction of
variability. Two noded semi-hardwood cuttings of seven ecotypes of
Plumbago rosea and one related species, Plumbago zeylanica were used
for the first experiment. The ecotype of P. rosea from College of
Horticulture, Vellanikkara was used for the second experiment. The
cuttings were treated with six doses of gamma rays (0.25, 0.50, 0.75,
1.00, 1.25 and 1.50 kR) and M I V I generation was evaluated.
Pollen germination was not noticed in P. rosea whereas the pollen
grams of P. zeylanica germinated. The germination of seeds was more
quickly in scarified seeds of P. zeylanica than seeds with intact seed
coat. All the pollination techniques failed to give any positive result on
seed set in P. rosea. Normal pairing of chromosomes were observed in
meiotic cells of both the species.








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All characters studied had significantly high genotypic correlation
with yield. High estimates of heritability (broad sense) was observed
for all characters studied. High estimates of heritability coupled with
high genetic advance was observed for plant height and root length which
indicate that direct selection for improvement of these traits will be
effective. Path coefficient analysis showed that dry root yield had
maximum direct effect on plumbagin content of roots and plant height had
maximum direct effect on fresh and dry root yield. The index score for
selection was highest for P zeylanica followed by the ecotype of P rosea
from Kottayam.
EDso of gamma rays for the stem cuttings of P rosea was 1.685 kR.
The sprouting percentage of cuttings was significantly decreased
with increased doses of mutagen. Progressive delay in sprouting was
noticed as the level of dose increased. The percentage lethality was
higher in mutagen treated population than in the control. The optimum
dose for inducing maximum yield and yield attributing characters ranged
between 0.70 kR and 0.85 kR of gamma rays. High yielding mutants
were observed in plants treated with 1.0 kR of gamma rays.
The highest values for yield and yield attributing characters were
obtained for 0.75 and 1.00 kR gamma rays.
Gamma rays at 1.0 kR was most effective in inducing variability
for root yield.