Abstract
Solanum nigrum L., root calli have been induced on an axenic hypocotyl explants excisized from surface sterilized germinated seeds under tissue culture techniques using MS-medium supplemented with 0.3 mg.L-1 NAA and 2.0 mg.L-1 kinetin. Calli were then removed and exposed to different doses of fast neutrons (105, 106, 107, 108, and 109 n/cm2). The control and fast neutrons irradiated calli were then transferred and subcultured on MS media for 6 weeks and kept growing at 26oC under low light intensity. Callus irradiated with 107 n/cm2 fast neutrons produced the highest yield of callus on salt free medium as compared with the control. The irradiated calli with fast neutrons fleunces and the control were removed and subcultured on MS media containing different concentrations (0.0, 0.5, 1.0, 1.5 and 2.0 %) of NaCl and CaCl2 solution (9 :1 v/v). After 6 weeks of growth at 26oC under light intensity (1500 Lux). The calli exposed to 107 and 108 n/cm2 fast neutrons exhibited more salinity tolerance, and were able to continue their growth even under the higher level of salinity (2 % NaCl + CaCl2 (9 :1 v/v). However, calli exposed to 109 n/cm2 fast neutrons could not continue their growth under the higher level of salinity (2.0 %) and stop growth after salinity 1.0%. The data also revealed that salinity tolerance was positively associated with high accumulation of osmoprotectants, i.e. sucrose and proline into calli. The data also showed that, increasing the salinity level, induced an accumulation of Na+ content in the root calli; in contrast K+ and Ca++ contents exhibited a decrease in the root calli. The results obtained in the present work seem to indicate that fast neutrons can be successfully applied to improve salinity tolerance in Solanum nigrum root calli.

Key words: fast neutrons, salt tolerance, tissue culture, Solanum nigrum L.