Identification of Tobacco streak virus in Cranberry and the Association of TSV with Berry Scarring

Characterization of Blueberry shock virus, an Emerging Ilarvirus in Cranberry

Blueberry shock virus (BlShV), an Ilarvirus sp. reported only on blueberry, was associated with scarring, disfigurement, and premature reddening of cranberry fruit. BlShV was detected by triple-antibody sandwich enzyme-linked immunosorbent assay and reverse-transcription polymerase chain reaction, and isometric virions of 25 to 28 nm were observed in cranberry sap. The virus was systemic, although unevenly distributed in plants. The coat protein of BlShV from cranberry shared 90% identity compared with BlShV accessions from blueberry on GenBank. Phylogenetic analysis of isolates of BlShV from cranberry collected from Wisconsin and Massachusetts did not indicate grouping by state. BlShV was detected in cranberry pollen, and seed transmission of up to 91% was observed. Artificial inoculation of cranberry flowers by pollination did not cause virus transmission. In some Nicotiana spp., rub inoculation of leaves with homogenized BlShV-positive cranberry flowers resulted in systemic infection. Cranberry plants recovered from symptoms the year after berry scarring occurred but continued to test positive for BlShV. The virus caused significant reduction in the average number of marketable fruit and average berry weight in symptomatic cranberry plants but recovered plants yielded comparably with healthy plants. Although recovery may limit the immediate economic consequences of BlShV, long-term implications of single- or mixed-virus infection in cranberry is unknown.

Recovery of Cranberry Plants Infected With Tobacco streak virus and Incidence and Distribution of TSV in the Field

Tobacco streak virus (TSV) has been detected in cranberry plants in Wisconsin, New Jersey, and Massachusetts, and is associated with berry scarring symptoms. In the current study, cv. Mullica Queen plants that produced scarred, symptomatic, TSV-positive fruit in one year produced nonscarred, asymptomatic, TSV-positive fruit in subsequent years, consistent with the "recovery" phenomenon previously documented in other ilarvirus-woody plant interactions. In field trials, fruit set and berry weight were significantly reduced (P < 0.05) in symptomatic, TSV-positive cranberry shoots but not in recovered, TSV-positive shoots compared with healthy, TSV-negative shoots. Likewise, return bloom in the first year following berry scarring was not negatively impacted in recovered shoots. Detection of TSV in various plant parts throughout the growing season was more variable in symptomatic shoots than in recovered shoots. Of all plant parts tested, TSV detection was lowest in berries at the time of harvest in both symptomatic and recovered shoots. Minimal increases in incidence of TSV-infected shoots in cranberry beds from one year to the next, and spatial autocorrelation of TSV-infected shoots, suggest that most new infections result from TSV spreading within a bed, rather than frequent introductions of the virus from external sources.