Effects of reduced nitrogen source and sucrose concentration on varietal differences in rice [Oryza sativa] cell culture

Effects of changes in medium composition on callus proliferation vvere examined in five varieties including Koshihikari and Norin No. 1, which could not be easily handled in cell culture. Calluses were induced from mature embryos and were transferred into liquid media with various compositions. Sucrose concentration affected differences ingrowth rates among the calluses from the five varieties. The differences in growth rates were smaller at a concentration of 0.375 % sucrose in any of the four media Tvit.h various compositions of nitrogen sources than at a concen-tration of 3 % sucrose. Reduced nitrogen ssource alsoaffected the varietal differences in growth rates. At a concentration of 0.375 % sucrose, the growth rates of the Koshihikari and Norin No. I calluses were lower than those of the calluses from other varieties in the media con-taining 20 mM potassium nitrate (KN03), 20 mM KNO3 and 2.5 mM ammonium sulfate ((NH4)2S04) or 20 mM KN03 and 5mM glutamine as nitrogen source, while thegroTvth rates of the Koshihikari and Norin No. I caluses were almost identical With those of the calluses from othe varieties in the medium containing 2O mM KNO3 and 5 mM alanine. In the nex. t experiment, changes in the medium pH, which were induced by the growth of the calluses, were monitored at a concentration of 0.375 % sucrose during the culture period and were compared between Nipponbare and Koshihikari.