FIELD TESTING OF A SATELLITE-CONTAINING ATTENUATED STRAIN OF CUCUMBER MOSAIC-VIRUS FOR TOMATO PROTECTION IN JAPAN

A potentially useful, attenuated cucumber mosaic virus (CMV), CMV-KO2, was isolated from a tomato field in Japan. The virus had an associated nonnecrogenic satellite RNA (SatRNA) containing 368 nucleotides with microsequence heterogeneity and a unique sequence in positions 79-87 compared to previously reported SatRNAs. Experimental infections in tomato plants showed that the concentration of CMV-KO2 was maintained stably at low levels, and it was not transmitted from tomato to tomato by Myzus persicae. A host-range study of 32 cultivars of 20 species from eight families showed that CMV-KO2, in general, caused either no symptoms or mild symptoms on those plants. No synergistic effect caused by mixed infections of CMV-KO2 and tobacco mosaic virus or potato virus Y was observed in tomato plants. Field tests during 1989 and 1990 revealed that tomato plants treated with CMV-KO2 had a 20-200% higher yield (20-40 t/ha) compared to nontreated plants in CMV-infested fields. Collectively, the results indicate that CMV-KO2 is useful and safe to use.