First report of nerine latent virus in ornamental crinum in the United States

Authors: Jordan, Ramon; WINGERT, MITCH - Biotechnology Academy; LOUDEN, CHASE - Biotechnology Academy; GUARAGNA, MARY ANN - Former ARS Employee

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2018
Publication Date: 1/24/2018
Citation: Jordan, R.L., Wingert, M., Louden, C., Guaragna, M. 2018. First report of nerine latent virus in ornamental crinum in the United States. Plant Disease. 102:1469. doi.org/10.1094/PDIS-09-17-1512-PDN.
DOI: https://doi.org/10.1094/PDIS-09-17-1512-PDN

Interpretive Summary: Ornamental flower bulbs (including true bulbs, bulbils, corms, tubers and rhizomes) are important floriculture crops in the U.S. Crinum is a large genus of herbaceous perennial flowering bulbs grown primarily in the summer for their large, showy, fragrant flowers. In 2015, ARS scientists in Beltsville, MD discovered mosaic symptoms on the leaves of several Crinum plants growing at the US National Arboretum, Washington, DC. They isolated a virus from these symptomatic plants and determined that the disease-associated virus was a unique isolate of Nerine latent virus (NeLV). NeLV had previously been reported in several other ornamental plants in Australia, China, the Netherlands, and Taiwan. To our knowledge, this is the first report of NeLV infecting Crinum and the first report of NeLV in the United States. The information and tools developed in this work will be useful to state and federal regulatory officials to make timely and appropriate recommendations in safeguarding the movement of horticultural products into and throughout the U.S.

Technical Abstract: Ornamental flower bulbs (including true bulbs, bulbils, corms, tubers and rhizomes) are increasingly important floriculture crops. Crinum is a large genus of herbaceous perennial flowering bulbs in the family Amaryllidaceae. Most of the Crinum species are grown in the summer and have large, showy, white, pink, deep rose, or even striped fragrant flowers borne on 2- to 5-foot stalks. Only a few viruses have been reported to infect cultivated Crinum. These include three potyviruses: Nerine yellow stripe virus in India, Hippeastrum mosaic virus in the U.K., and Crinum mosaic virus in Australia, DC, FL and HI, and a tospovirus. In April, 2015, mosaic symptoms were observed on the leaves of several Crinum plants growing at the US National Arboretum, Washington, DC. Typical filamentous virus-like particles were observed by electron microscopy of leaf-dip preparations from symptomatic leaves. However, these samples were negative in ELISA tests using our POTY Group Test monoclonal antibody PTY-1. Three independent samples of total RNA from leaves of one individual Crinum plant (cultivar Mo’Pon) were isolated and used for custom cDNA library preparation, which included rRNA depletion, and using NEBNext Ultra RNA Library Prep protocols. Three cDNA libraries (consisting of ~300bp fragments) were sequenced using paired-end next-generation protocols on an in-house Illumina MiSeq. Raw sequence reads (8,798,332 250bp reads) were trimmed of adaptor linkers using MiSeq software and de novo assembled into contiguous sequences using Geneious Pro R9. Contig sequences were subjected to BLASTX analysis against known viral sequences in GenBank (NCBI) databases. An 8,333 bp contig showed 78-96% identity with carlavirus Nerine latent virus (NeLV) sequences. A total of 269,897 reads could be mapped against a reference NeLV genome sequence (GenBank #NC_028111) with a maximum coverage of 7,662-fold. Pair-wise analyses of the predicted 297 AA coat protein (CP) sequence had 90-99% sequence identity with NeLV isolates from other ornamentals such as Hippeastrum (Netherlands, Taiwan), Ismene (Netherlands), Lycoris (Taiwan), Narcissus (Australia, China, Taiwan), and Nerine (Netherlands); and, only 33-48% sequence identity with other carlaviruses infecting Amaryllis, Helleborus, Hippeastrum, Narcissus and Nerine. To confirm the presence of NeLV in the original Mo’Pon sample and three other crinum plants: NeLV-specific CP primers were designed from the consensus full genome sequence and used in RT-PCR reactions with total RNAs isolated from these four Crinum plants. NeLV was detected in the original and one other plant. To our knowledge, this is the first report of NeLV infecting Crinum and the first report of NeLV being detected in the US.