A COMPARISON OF METHODS FOR DIRECT GENE-TRANSFER INTO MAIZE (ZEA-MAYSL.)

Techniques for transforming intact tissues of cereals were evaluated f or their efficacy in transforming immature embryos and Type II callus of maize (Zea mays L.). The techniques used were particle bombardment, tissue electroporation. tissue electrophoresis, and silicon carbide f ibers, Each method was assessed in terms of transient beta-glucuronida se (GUS) expression, High levels of GUS expression sere observed in A1 88 Type II callus using both tissue electroporation and particle bomba rdment, with means of 417.8 and 954.5 blue expression units (beu) per g fresh weight (FW) callus, respectively. Only particle bombardment re sulted in high transient gene expression in immature embryos, with a m ean transformation frequency of 34.8 b.e.u. per embryo. Very low level s of GUS expression were achieved with silicon carbide-mediated gene t ransfer. even when employing tissues used in the original publication (Black Mexican Sweet suspension cells). GUS expression was not obtaine d following tissue electrophoretic gene delivery.