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Letter to the Editor

Persistence: A Vector Relationship Not Applicable to Fungal Vectors. R. N. Campbell. Department of Plant Pathology, University of California, Davis 95616. Phytopathology 83:363-364. Accepted for publication 8 January 1993. Copyright 1993 The American Phytopathological Society. doi:10.1094/Phyto-83-363.

As the study of fungal vectors of plant viruses developed, two types of virus-vector relationships were established (3,6,13,18,19). These relationships, which have been reviewed in detail (4), were defined by whether the virus was acquired in vivo or in vitro and by whether the virus survived externally or internally to the resting spores in the absence of a living host plant. Because these characteristics were correlated, only two groups were defined: one in which the viruses were acquired in vitro and survived externally to the resting spore and one in which viruses were acquired in vivo and survived internally. Hence, the groups can be designated either by the method of acquisition or by the site of virus survival. Both groups have been confirmed (1,9,15). The only qualification to this terminology is recognition that in vitro acquisition is not restricted to a laboratory environment but also occurs in a natural setting when a virus is adsorbed by zoospores in soil water (4).