Induction and evaluation of genetic variability in chethikoduveli

Abstract

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.

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.