Simplified construction and performance of a device for particle bombardment

A modified particle inflow gun (PIG), that utilized a plastic vacuum chamber, was compared with a conventional PIG by bombarding cantaloupe (Cucumis melo L.) cotyledon basal quarters with plasmid pBI221 (Clontech Inc.) containing a β-glucuronidase (GUS) gene adsorbed onto tungsten particles. Both guns produced an equivalent number of transient GUS 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 lower pressure and/or the greater distance generally produced significantly fewer GUS-positive foci. The plastic PIG was convenient to operate and could be built with simple hand tools in less than 40 minutes, using readily available parts.