A novel caulimovirus associated with a complete fruit drop symptom in 'Bluecrop' blueberry

Here we describe the nucleotide sequence and genome organization of a novel virus in the family Caulimoviridae from 'Bluecrop' blueberry plants that exhibited fruit drop symptoms. The virus is tentatively named Blueberry fruit drop associated virus (BFDaV). Blueberry fruit drop disease (BFDD) was first observed near Abbotsford, British Columbia, Canada in the late 1990s, and subsequently in a single field in northern Washington state in the US in 2012. Infected bushes drop fruit several weeks prior to harvest and at harvest the affected plants appear taller than healthy ones as there is no fruit weighing down the branches. The virus was amplified initially from diseased material using rolling circle amplification. The full genome of BFDaV was 9,850 bp in length, and contained a single open reading frame, encoding for a polyprotein and contains a large noncoding region. Based on phylogenetics and the genome size and organization, BFDaV is proposed as a new member of the family Caulimoviridae, and will likely represent a new genus. When mapping part of a field with BFFD, there was a nearly perfect correlation between the presence of the virus and fruit drop symptoms. Additionally, the fruit drop symptoms have only been observed in the cultivar 'Bluecrop' and other cultivars in adjacent blocks have tested negative for BFDaV after 6-20 years of exposure.