First report of constricta yellow dwarf virus infecting Lobelia in the United States and the world.

Abstract

Blue cardinal (Lobelia siphilitica L., family: Campanulaceae) is a popular perennial ornamental plant. Lobelia spp. have been reported as hosts of economically important viruses including cucumber mosaic virus (Nameth and Fisher, 2001), turnip mosaic virus (Lockhart et al., 2002), and tomato spotted wilt virus (Brown, 1988). During fall 2022, in a garden in Fayetteville, Arkansas, USA, yellow speckling, chlorosis, and dwarfing were observed on several cardinal plants. Three symptomatic plants were sampled, and RNA was isolated as described in Poudel et al. (2013) and pooled. Material was sequenced using the MinION platform as described by Liefting et al. (2021). A total of 56,700 raw reads (mean-length 326) were analyzed using VirFind (Ho and Tzanetakis, 2014) revealing 23 contigs ranging from 209-12,776 nucleotides (nt) which showed 96.2-98.4% identity with constricta yellow dwarf virus (CYDV; genus Alphanucleorhabdovirus, KY549567) and 16 contigs ranging from 201-531 nt with 83.4-95.7% identity with hydrangea chlorotic mottle virus (HdCMV; genus Carlavirus, EU754720). A total of 6,387 reads were mapped to the CYDV genome (KY549567) with 181x average coverage per nucleotide, and the consensus sequence of 12773 nt shared 98.1% identity to KY549567. The results were verified by RT-PCR and sequencing of the amplicons using primers 8825F: 5'-ACCCTGAGACAGGCATTGTG-3' and L2 9760: 5'-GCCGTACTATGAGAAGGGGC-3' for CYDV and 6495F: 5'-CAAGTACGTCTGTGTGAGGT-3' and 6630R 5'-CTTTTTGATAGTGTCATTGCTACC-3' for HdCMV. RNA was subsequently extracted from eight symptomatic and 12 symptomless samples. All symptomatic samples tested positive for CYDV but none of the 20 was positive for HdCMV indicating that CYDV is possibly the causal agent of the observed symptoms. Amplicons were CYDV specific and showed 91-98% nt identity (99-100% amino acid identity) (accession No. OP998261-63) with the CYDV isolate from Solanum tuberosum (KY549567). To the best of our knowledge, this is the first report of CYDV infecting L. cardinalis in the USA and the world. CYDV has been reported as an important pathogen of potato in the USA and recent reports indicate that emergence and re-emergence of rhabdoviruses on new hosts worldwide may threaten agricultural production (Bejerman et. al., 2021). Given the lack of monitoring of cardinal plants for viruses, this could serve as a reservoir of CYDV for several vegetables and ornamental crops (Jang et al., 2017).