# Virome Analysis of Lemon Plants with Vein Clearing Symptoms Reveals Mixed Infection of Citrus Vein Clearing Virus, Iris Domestica Betaflexivirus 1 and Hop Stunt Viroid

## TL;DR

This study found that lemon plants with vein clearing symptoms are infected by multiple viruses and a viroid, including a previously unreported virus.

## Contribution

The first report of IDBV in lemon plants and evidence of mixed infections contributing to disease symptoms.

## Key findings

- Mixed infection of CYVCV, IDBV, and HSVd was identified in lemon plants with vein clearing symptoms.
- IDBV was confirmed in two additional lemon plants using specific primers.
- Phylogenetic analysis suggested possible origins of the viruses and viroid in lemon.

## Abstract

Citrus yellow vein clearing virus (CYVCV) is the causative agent of the yellow vein clearing disease (YVCD), a worldwide and highly destructive disease in lemon (Citrus lemon) and sour orange trees (C. aurantium). The typical symptoms of vein clearing are believed to be associated with CYVCV infection in citrus, so virus-specific diagnostic systems are currently used to confirm infection. In the present study, virome analysis based on high-throughput sequencing (HTS) on a lemon plant showing YVCD revealed mixed infection of CYVCV, iris domestica betaflexyviridae 1 (IDBV), and hop stunt viroid (HSVd). This multiple infection was confirmed in other two lemon plants with similar symptoms using virus/viroid specific primers. This is the first report of IDBV in lemon. Through molecular characterization and the reconstruction of phylogenetic relationships, a possible origin of the viruses/viroid identified in lemon has been hypothesized. Such mixed infections raise new questions about their role in the expression of YVCD symptoms observed on lemon.