Effects of Gamma Radiation on In Vitro Multiple Shoot Formation of Aromatic Rice Seeds (Oryza sativa L.)

Abstract

The effect of exposure dose of gamma radiation on multiple shoot formation of aromatic rice seeds (Oryza sativa L. cv. Khao Dawk Mali 105) was investigated . The seeds were irradiated by gamma radiation with varying exposure doses of 0, 4, 8, 12, 16, 20, 25, 28, 32, 36, 40 and 44 krad. After irradiation, the seeds were surface sterilized and cultured on Murashige and Skoog medium supplemented with benzyladenine 25 mg/l to induce multiple shoot formation. After 5 weeks cultured the number of multiple shoot – forming seeds and the number of shoots per seed were counted. It was found that the number of multiple shoot-forming seeds was increased from 45.9% in the control to 83.3% in seeds irradiated at 24 krad. At the exposure dose of 28 krad the number of multiple shoot –formation seeds was decreased to 80% and was lowest (11.4%) at 40 krad. Multiple shoots formation was completely inhibited at the highest exposure dose of 44 krad. The exposure dose required to reduce the number of multiple shoot – forming seeds by 50 percent (RD50) was 38 krad. Similarly, the number of shoots per multiple shoot-forming seed was increasing as the exposure dose increased from 5.7 shoots in the control to 21.3 shoots in seeds irradiated at 40 krad, The number of shoots per seed was zero at the exposure dose of 44 krad. The multiple shoots regenerated from irradiated seeds were rooted. Then the M₁R₁ plantlets were transplanted into pots grown under greenhouse conditions.