OBTAINMENT AND CHARACTERIZATION OF RICE CLONES RESISTANT TO STRESS FACTORS

A scheme of cell selection of rice (Oryza sativa L.) for salt toleranc e is developed in the present work. Callus tissue was obtained from ma ture embryos of the Soyuznyi-244 salt-intolerant rice cultivar on MS m edium + 4 mg/liter 2,4-D. Sodium chloride (1.5%), PEG (20%), and ethio nine (0.7 mM) were used as selective factors. Without any mutagen, ada ptive variants were isolated that died in the course of 3-5 subculture s during subsequent subcultivation under selective conditions. Stably resistant cell lines were obtained and characterized after treatment o f callus tissues for a period of 1 h with N-nitroso-N-methylurea in a concentration of 4 mM and subsequent culling under selective condition s. The frequency of their emergence was approximately the same in all selective systems and constituted 10(-6). The selective factor determi ned the type of stabilization of cell lines. Gradual elimination of ad aptive variants occurred where ethionine was used. In osmotically acti ve systems (with NaCl and PEG), actively growing and non-growing colon ies were recorded in the first subcultures. The growth rate of the for mer did not vary throughout the next seven subcultures under selective conditions, whereas non-growing colonies died after checking of stabi lity of the trait. Cross checking of resistance of the obtained clones made it possible to isolate cell lines resistant to two and three sel ective factors.