Gamma ray induced small flower mutant in Hibiscus rosa-sinensis

Induced somatic mutation breeding has been highly effective in the improvement of vegetatively propagated ornamental crops, which has greatly contributed to India's economic growth. Most ornamentals are in great demand, for their aesthetic appeal as well as for their multifarious uses. Hibiscus rosa- sinensis, family Malvaceae, a native of China, is grown as an ornamental plant throughout India. It is an evergreen, woody, glabrous, showy shrub, 5-8 feet high, leaves bright green, flowers solitary axillary, bell shaped, large, 4-6 inches in diameter with pistil and stamens projecting from the center, capsule roundish and many seeded. Cuttings propagate this plant because it never produces seed in India. The flowers are eaten either raw or pickled in China and the Philippines. Crushed flowers produce a dark purplish dye that was used for polishing shoes in China and other countries, and also used for coloring hair and eyebrows. The flowers contain carotene and plants are also used as fodder. Recent research has shown that the flowers have post-coital antifertility activity. The presence of potent antiestrogenic activity in flowers may be responsible for terminating pregnancy, as tested and reported for rats. The cuttings (size 12 cm) of Hibiscus rosa- sinensis were irradiated with 60Co source of gamma rays at 5, 10, 20, 30, 50, 70 and 100 Gy to induce mutation. Three replicates of 20 cuttings each for every dose were separately planted in 6-inch earthen pots with equal number of cuttings for control to raise the VM1 generation and all replicates were maintained under glasshouse condition. All flowers produced throughout the blooming period in control and irradiated plants were carefully examined to detect the somatic mutations in flower shape and size. No changes were observed in control population. The variants for different morphological characters were isolated from VM1 generation. At 10 Gy a mutant plant was detected, which produced 5 flowers in the first blooming season and all of them were significantly small in size as compared to the control. The average length of petals in control was 5.2 cm while that of the mutant was 3.3 cm and the width at the broadest point was 3.0 cm for control and 1.6 cms for the mutant. The color and aestivation of the mutant was like the control. The mutant was a chimera, as out of 22 cuttings of the mutant plant used to raise VM2 population, only 2 plants (9%) produced small flowers and these are being further multiplied. Floral variants obtained at other doses showed variation in the length and orientation of the style, number and size of anthers and also flower colour and are being studied