A study of the mechanisms controlling the host range of plant viruses: II. The host range of hybrid viruses reconstituted in vitro and of free viral RNA

It was found that (1) hybrid virus consisting of cucumber virus 4 (CV4) protein and tobacco mosaic virus (TMV) RNA was able to infect Nicotiana glutinosa L., Chenopodium amaranticolor Coste & Reyn, and Phaseolus vulgaris L. plants resistant to CV4. Interference between CV4 protein and “CV4 protein × TMV RNA” hybrid suggested the presence of CV4-specific receptors in C. amaranticolor cells; (2) hybrid virus consisting of CV4 protein and potato virus X (PVX) RNA was also able to infect N. glutinosa; (3) hybrid virus consisting of TMV protein and bromegrass mosaic virus (BMV) RNA was not able to infect Hordeum vulgare L., Zea mays L. (plants resistant to TMV), or N. glutinosa, although the virus contained RNA able to infect H. vulgare plants. The hybrid virus was able to infect Chenopodium quinoa Willd., a host for both TMV and BMV; (4) hybrid virus consisting of TMV protein and CV4 RNA was able to infect Cucumis sativus L., but not N. glutinosa; (5) hybrid virus consisting of TMV protein and PVX RNA was able to infect Datura stramonium L., Gomphrena globosa L., N. glutinosa, and C. amaranticolor; hybrid viruses consisting of BSMV RNA and TMV or CV4 protein were entirely noninfective. RNA preparations from TMV, barley stripe mosaic virus (BSMV), CV4, and PVX were unable to infect any of nonhost plants tested. The possibility of multiple blocking of virus infection at different stages of replication is suggested.