First reports of Apple Luteovirus 1, Apple rubodvirus 1 and Apple hammerhead viroid infecting apples in Belgium.
For a pilot study on germplasm collections, leaves were collected from six apple trees (Malus domestica) numbered Q9, Q27, Q35, Q37, Q39 and Q41 in a Belgian experimental orchard (CRA-W) in June 2019 and June 2020. At the time of sampling and during subsequent visits, no viral symptoms were observed on the trees. However, Apple Luteovirus 1 (ALV-1) has been identified in trees with rapid apple decline, Apple rubodvirus 1 (ARWV-1) is associated with apple rubbery wood disease, and Apple hammerhead viroid (AHVd) infection presents variable symptoms including swelling or limb flattening. Double-stranded RNA (dsRNA) was extracted from all trees except Q9, reverse-transcribed and amplified (RT-PCR) for high-throughput sequencing. Total RNA was extracted from tree Q9 using the RNeasy Plant Mini Kit. BLASTn analysis and RT-PCR confirmed the presence of ARWV-1, ALV-1, and AHVd. This is thought to be the first report of ARWV-1, ALV-1, and AHVd in Belgium.