Characterization of a zucchini yellow mosaic virus isolate with a deficient helper component.

Two isolates of zucchini yellow mosaic virus (ZYMV) were found to be either highly (HAT) or poorly (PAT) aphid-transmissible. The inefficient transmission of ZYMV-PAT was independent of the virus source plant or aphid species used. The ZYMV-PAT and ZYMV-HAT, from which the former was derived, did not differ in their host range or serological properties. Purified virions of either ZYMV-HAT or ZYMV-PAT were readily transmitted by aphids when crude or concentrated helper component (HC) from ZYMV-HAT was provided, but were not transmitted when mixed with crude or concentrated HC from ZYMV-PAT (...)