SIMPLIFIED CONSTRUCTION AND PERFORMANCE OF A DEVICE FOR PARTICLE BOMBARDMENT

A modified particle inflow gun (PIG), that utilized a plastic vacuum c hamber, was compared with a conventional PIG by bombarding cantaloupe (Cucumis melo L.) cotyledon basal quarters with plasmid pBI221 (Clonte ch Inc.) containing a beta-glucuronidase (GUS) gene adsorbed onto tung sten particles. Both guns produced an equivalent number of transient G US foci when tested at 410 kPa (60 psi), 620 kPa (90 psi) or 830 kPa ( 120 psi) helium and at a 10, 15 or 20 cm gap between the specimen and DNA/particle holder screen. For both guns, treatments utilizing the lo wer pressure and/or the greater distance generally produced significan tly fewer GUS-positive foci. The plastic PIG was convenient to operate and could be built with simple hand tools in less than 40 minutes, us ing readily available parts.