Replication and Movement of a Coat Protein Mutant of Cymbidium Ringspot Tombusvirus. Tamás Dalmay. Agricultural Biotechnology Center, P.O. Box 170, H-2101 Gödöllö, Hungary. Luisa Rubino(2), József Burgyán(1), and Marcello Russo(2). (1)Agricultural Biotechnology Center, P.O. Box 170, H-2101 Gödöllö, Hungary; and (2)Dipartimento di Protezione delle Piante, Universitá degli Studi and Centro di Studio del CNR sui Virus e le Virosi delle Colture Mediterranee, 70126 Bari, Italy.. MPMI 5:379-383. Accepted 25 June 1992. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1992.

The spread of cymbidium ringspot tombusvirus (CyRSV) in host tissue was studied by using a coat protein gene mutant with a six-nucleotide deletion; the deletion removes two amino acids from the shell domain (S) of the capsid protein. Mutated protein subunits were synthesized in infected cells but could not assemble into virus particles. Virions were formed, however, with inoculation of mutated RNA in transgenic plants expressing normal CyRSV coat protein. The mutant is restricted in long-distance movement in Nicotiana clevelandii, whereas it spreads systemically in N. benthamiana. These results suggest that tombusviruses may spread either as complete virions or in a nonvirion form, depending on the host plant species.