Soybean [Glycine max (L.) Merrill] embryogenic cultures: The role of sucrose and total nitrogen content on proliferation

To improve proliferation of soybean cultures in liquid medium, the effects of sucrose; total inorganic nitrogen; content of NO3-, NH4+, Ca2+, PO43-, K+; NH4+/NO3- ratio; and medium osmotic pressure were studied using cv. Jack. Sucrose concentration, osmotic pressure, total nitrogen content, and ammonium to nitrate ratio were found to be the major factors controlling proliferation of soybean embryogenic cultures. Growth decreased linearly as sucrose concentration increased from 29.7 mM to 175.3 mM. A sucrose concentration of 29.2 mM, a nitrogen content of 34.9 mM at 1 to 4 ammonium to nitrate ratio were found to be optimal for the fastest proliferation of soybean embryogenic cultures. There was no significant effect on proliferation of cultures when concentrations of NH4+, Ca2+, PO43-, and K+ were tested in the range of 3.50 to 10.50, 1.02 to 3.06, 0.68 to 2.04, and 22.30 to 36.70 mM, respectively. The relative proliferation of embryogenic cultures of four soybean genotypes was evaluated in Finer and Nagasawa medium and in the new medium formulation. Despite genotype-specific differences in growth, the genotypes tested showed a biomass increase in the new formulation equal to 278, 269, 170, and 251% for Chapman, F138, Jack, and Williams 82, respectively, relative to their growth on standard FN medium. Due to its lowered sucrose and nitrogen content, we are referring to the new medium as FN Lite.