II. 15. Enhancement of gamma ray-induced mutation frequency in barley by post-treatment with Ethidium bromide (EB).
J. Singh, B. N. Singh and R. M. Singh, Department of Genetics and Plant Breeding, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi 221 005, India.
In recent years, studies on combined treatment with different mutagens have shown that the efficiency of one mutagen can be modified by combining it with another mutagen. The acridine compound, ethidium bromide (EB) has been reported to induce nuclear as well as cytoplasmic mutations in higher plants (Levy and Ashri, 1975; Burton and Hanna, 1976). In the present study, EB (2, 7-Diamino-10-ethyl-0-phenyl-phenanthridinium Bromide) was chosen as the mutagentic agent in combination with gamma rays to evaluate its efficiency in producing chlorophyll mutations in barley (Hordeum vulgare L.).
Seeds of a six-rowed hull-less barley var. 'IB 165' were irradiated with 15 kR doses of 60Co gamma rays. Half the irradiated seeds and fresh control seeds were presoaked in distilled water for 1 hr and then treated with 1000 ppm solution of EB for 6 hr at 23°C + 1°C. Another lot of fresh seeds were soaked in distilled water to serve as control. The treated and control seeds were grown in the field and at maturity, all the M1 plants were harvested treatmentwise. During the rabi season of 1981, the M2 generation was grown in the field. At the seedling stage, different types of chlorophyll mutations were scored and reported as per 1000 M2 seedlings.
It is evident from Table 1 that in treatment with 15 kR gamma rays various chlorophyll mutants occurred at a frequency of 6.62 per 1000 M2 seedlings, but treatment with EB alone produced no mutations. However, in combined treatment of EB with gamma rays, a significant enhancement in M2 chlorophyll mutation frequency (16.29 per 1000 M2 seedlings) and spectrum were observed. It has been suggested that mutagens in combined treatments, besides initiating changes in DNA, may also affect the fixation or recovery of potential mutations (Sharma, 1970; Singh et al. 1977).
The results of the present study suggest that using EB as post-treatment in combination with gamma rays will achieve a higher mutation frequency and spectrum in barley.
References:
Burton, G. W. and W. W. Hanna. 1976. Crop Sci. 16:731-732.
Levi, A. and A. Ashri. 1975. Mutation Res. 28:397-404.
Sharma, R. P. 1970. Indian J. Genet. 30(1):180-186.
Singh, R. M., J. Singh and A. N. Srivastava. 1977. BGN 7:60.
