Studies on radiation sensitivity in some Bougainvillea cultivars

Abstract

The present investigation was on relative radiation sensitivity, sprouting behavior, morphological variations, pollen fertility and finally selection of desirable mutants in three Bougainvillea cultivars viz., ‘Dr.R.R.Pal’, ‘Lady Mary Baring’ and ‘Stanza’. The survival percentage estimated in three cultivars was found to vary widely. The LD 50 for ‘Lady Mary Baring’, it was 2.0 kR. Detailed studies on the morphological abnormalities with exposure to gamma rays revealed that the cuttings were very sensitive to radiation. The abnormalities observed in leaves include asymmetrical development of leaf blade, variation in size, notching, mottling and bilobed conditions in some of the leaves of the cuttings treated with more than 1.0 kR of gamma rays. Stimulation in plant height was observed at 1.0 kR in ‘Dr.R.R Pal,’ and ‘Stanza’ and in ‘Lady Mary Baring’ at 2.0 kR of gamma rays. An interesting induced somatic mutant in cv. ‘Lady Mary Baring’ was observed with changes in flower and bract colour in one of the well established plants at 3 kR of gamma rays. The bract colour was completely changed to light pink as compared to Indian yellow in the parent cultivar. The flower tube was changed to light green and star colour was changed to light yellowish green with the backside of star changed to pink. In ‘Stanza’ one of the interesting features observed was partial leaf variegation in two of the leaves at 2.kR. The mature leaves showed cream yellow variegation on one side of the margin. However, other leaves in this branch were normal. Rooting behavior varied widely in the cultivars after exposure to gamma rays. In Dr.R.R Pal, the development of adventitious and lateral roots was minimum at 1.0 kR, followed in ‘Lady Mary Baring’ at 1.5 kR and ‘Stanza’ at 2.0 kR. The pollen fertility estimated in all the three cultivars in the treatments showed that the pollen grains were shriveled and deformed and they failed to take the stain confirming sterility as in the parent cultivars.