AgNO3 increases type II callus production from immature embryos of maize inbred B73 and its derivatives

Incorporating 10 to 100 μM AgNO3 into Phytagel(™) (0.2%) solidified N6 medium containing 1 mg/L 2,4-D, 100 mg/L casamino acids and 25 mM praline (N6 1-100-25) promoted type II callus production from cultured Zea mays L. immature embryos of FRB73, B73 X A188 and a proprietary B73 BC6 genotype. Under these conditions, approximately 15, 80 and 80% of the respective FRB73, B73 X A188 and B73 BC6 explants produced type II calli after 2 to 3 weeks incubation in the dark at 28 C. In the absence of AgNO3, the type II culture response from B73BC6 immature embryos was 25% on N6 1 100-25 solidified with Phytagel(™) (0.2%) as compared to 0% for that solidified with 0.8% agar. Duncan's medium was tested using 10 to 100 μm AgNO3 and generally promoted type I callus initiation, although up to 6% of the explants produced type II cultures in the presence of 0.2% Phytagel(™). Ethylene emanation rates of up to 370 and 115 nL g-1 h-1 were detected from B73 X A188 immature embryos and calli, respectively, cultured on N6 1-100-25.