• Journal of Plant Biotechnology
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• v.5 no.1
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• pp.43-49
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• 2003

Resistant cell lines to azetidine-2-carboxylic acid (AZCA) were selected through rice embryo culture after mutagenic treatment of callus irradiated with 30,50,70,90 and 120 Gy. The optimum AZCA concentration for the selection of resistant cell lines was 3 or 4 mM AZCA considering $LD_{50}$ and the fresh weight of callus. Survival rate of the AZCA resistant callus showed remarkable increase in the callus irradiated with 50 and 70 Gy. Regeneration rate of the AZCA resistant callus was much lower on the whole. Ninety and 120 Gy increased the regeneration rate for calli selected from 3 and 4 mM AZCA, respectively. Based on fresh weight, survival rate and regeneration for selection of the AZCA resistant cell line, 50-90 Gy was considered as the optimum range of gamma irradiation. Irradiated calli selected from AZCA were more tolerant to NaCl than those from non-irradiated calli. It suggests that elevated resistance to osmotic stress resulted from mutagenic treatment. The level of free proline content in the AZCA resistant cell line was increased up to 3.5 times compared with that in the control. Proline content in the regenerant derived from the AZCA resistant cell line also increased to 1.7 times that from the control plants regenerated from callus grown in AZCA free medium. Selection of proline overproducing cell lines by in vitro mutagenesis was successful and seems to be useful for improvement of stress tolerance in this crop.