Gal-On, A., Department of Virology, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
Meiri, E., Department of Virology, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
Huet, H., Department of Virology, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
Hua, W.J., Department of Virology, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
Raccah, B., Department of Virology, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel
Gaba, V., Department of Virology, Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50-250, Israel

Particle bombardment is a very efficient method for transfecting plants with a cloned RNA virus, or with transcripts. An infectious full-length cDNA clone of the RNA genome of the potyvirus zucchini yellow mosaic virus (ZYMV) was constructed under the control of the cauliflower mosaic virus 35S promoter. Inoculation by particle bombardment at the cotyledon stage with the cloned cDNA of ZYMV infected 100% of squash, cucumber, melon, and watermelon plants, compared to mechanical inoculation (0-19%). Bombardment technology is one million times more effective than mechanical inoculation. Due to the huge increase in efficiency, non-infective constructs now become infective i.e. infection by cDNA under the control of the 35S promoter without the NOS terminator and with an addition of 127 nucleotides between the promoter and the 5′ end of the viral cDNA. The infectivity of capped transcripts becomes 100%. Inoculation by particle bombardment produced visual symptoms rapidly (3-4 days), allowing the detection of viral coat protein after 2 and 3 days in systemic infected leaf and inoculated cotyledon respectively. Bombardment technology therefore permits rapid biological evaluation of constructs encoding viral genomes, and of transcripts from such constructs.