Irregular Occurrence of Rhabdoviruslike Particles in Tissues of Fragaria vesca Plants Infected with Strawberry Crinkle Virus

Abstract

AbstractWhen evaluated by electron microscopy, rhabdoviruslike particles (RLP) were found most frequently in petioles, less frequently in midribs, and not at all in roots or petals of Alpine strawberry plants leaflet graft‐inoculated with strawberry crinkle virus (SCV). In graft‐inoculated plants RLP were found only in mesophyll and phloem parenchyma cells and in sieve tubes. Numbers of RLP detected were highest within one week of the onset of symptoms, decreased with time, and were extremely variable, both among identically treated Alpine seedlings that showed similar crinkle disease symptoms and within Alpine clones. Through electron microscopy we were not able to predict if a given petiole sample from a graft‐inoculated Alpine plant showing typical symptoms of crinkle disease would have no, moderate, or many RLP. The percentage of Alpine plants developing crinkle symptoms after leaflet graft inoculation with symptom‐bearing leaves from a crinkle source was higher in summer than in winter. It was not increased after the source plants had broken dormancy in the spring, compared to plants kept vegetative all winter, and was not dependent on the length of time a symptom‐bearing source plant had been infected. When symptomless leaves from SCV‐infected Alpine plants were grafted to healthy Alpine indicator plants, no symptoms developed on the latter.