Viral satellite RNAs for the prevention of cucumber mosaic virus (CMV) disease in field-grown pepper and melon plants

A benign viral satellite RNA, in combination with a mild strain of cucumber mosaic virus (CMV-S), was used as a "vaccine" or "preinoculum" to demonstrate the feasibility of protecting pepper (Capsicum annuum cv. California Wonder) and melon (Cucurbita melo cv. Janus des Canaries) against two severe CMV strains, CMV-D and CMV-16, in the final 2 years of a 4-year pilot field and greenhouse experiment. In the field, healthy pepper and melon seedlings challenged with CMV-D and CMV-16 reduced yields by 33 to 60%; CMV-S caused only limited yield reduction in pepper and had no effect on the yield of melon. Different time intervals between preinoculation of pepper and melon seedlings with CMV-S and challenge inoculation with the severe CMV strains were tested. All plants challenged 3 weeks after vaccination showed nearly complete protection from subsequent infection by severe strains. The yield from preinoculated and challenged pepper plants was 80% that of untreated plants, while the yield from preinoculated and challenged melon plants was increased slightly over the untreated control plants. The use of this technology for biological control of plant viruses is discussed.