Symptomless infection by strawberry virus 1 (StrV-1) leads to losses in strawberry yields

High-throughput sequencing has opened up possibilities of detecting new plant pathogens, especially viruses, with relative ease. However, information about biological characteristics and relevance to plant production is usually lacking. Recently, a new strawberry cytorhabdovirus named strawberry virus 1 (StrV-1) was described and characterized at a molecular level. The virus can be transmitted by aphids and is commonly found in commercial plantations. Here, we studied the impact of a sole StrV-1 infection on production in two strawberry cultivars—Darselect and Karmen. All plants infected with StrV-1 remained symptomless during the experiment. In general, Darselect was more resilient to StrV-1 infection, and the average yield per plant was nonsignificantly lowered by 11.7% over the 2-year experiment. In contrast, StrV-1 infection in cultivar Karmen led to a significant yield loss of 31.8%, indicating that the genetic background plays a role. While the average fruit weight and diameter were relatively unaffected, lower yields in infected plants stemmed from a significantly reduced number of inflorescences, by 23.6% and 29.6% in Darselect and Karmen, respectively, which resulted in a reduction in the average number of flowers per plant (decreased by 16.5% and 27.3%, respectively), and hence the number of fruits per plant (by 14.5% and 27.6%, respectively). The StrV-1 load was higher in spring than in autumn, and generally higher in the second year after infection, which corresponded to higher losses in the second harvest, especially in cultivar Karmen.