|GONG, JUNSU - Chungnam National University|
|JU, HYEKYOUNG - Chungnam National University|
|KIM, IK-HYUN - Chungnam National University|
|SEO, EUN-YOUNG - Chungnam National University|
|CHO, IN-SOOK - Chungnam National University|
|HU, WEN-XING - Chungnam National University|
|HAN, JAE-YEONG - Chungnam National University|
|KIM, JUNG-KYU - Chungnam National University|
|LIM, YOUNG PYO - Chungnam National University|
|LIM, HYOUN-SUB - Chungnam National University|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2019
Publication Date: 4/5/2019
Citation: Gong, J., Ju, H., Kim, I., Seo, E., Cho, I., Han, J., Kim, J., Lim, Y., Hammond, J., Lim, H. 2019. Sequence variations among 17 new radish isolates of turnip mosaic virus showing differential pathogenicity and infectivity in Nicotiana benthamiana, Brassica rapa, and Raphanus sativus. Phytopathology. 109:904-912. https://doi.org/10.1094/phyto-12-17-0401-r.
Interpretive Summary: Plant viruses reduce yield and quality in many crops, and are spread through seed, mechanical transmission or vectored transmission. Turnip mosaic virus (TuMV) has a wide host range, including ornamental crops as well as many vegetables crops. A number of resistance genes are available in various brassicaceous crops, including turnip, cabbage, and radish, but isolates of TuMV able to overcome several of these resistance genes have emerged, and new resistance genes must be identified to maintain crop yields and quality. Scientists in Korea collaborated with ARS scientists to study infectious clones of multiple isolates of TuMV isolated from Korean radish crops. They discovered three classes of mild isolates of TuMV and screened some of the isolates against commercial radish varieties. Further comparisons of the isolates may allow combining of resistance genes to obtain more durable TuMV resistance in radish and other brassica crops.
Technical Abstract: Infectious clones were generated from 17 new turnip mosaic virus isolates. Pairwise analysis of full-length sequences revealed genomic nt and polyprotein aa identities of >87.9% and >95.7%, respectively, with highest nt identities in CP, P1, and HC-Pro, and highest aa identities in HC-Pro (99.48%), CI (99.14%), and NIa-Pro (99.26%) genes. Phylogenetic analysis showed that all 17 TuMV isolates belong to the basal-BR group, together with three previously characterized Korean isolates (Han et al. 2016), divided between two subclades, and most closely related to isolates from Japan, Italy, Turkey, and China. Five clones (HJY1, HJY2, KIH2, BE, and prior isolate R007) had lower sequence similarities than other isolates and produced mild symptoms in Nicotiana benthamiana, falling into three sequence classes (HJY1, HJY2 and R007; KIH2; and BE) whereas the remaining isolates induced systemic necrosis. Symptom severity in radish and Chinese cabbage was not correlated with that in N. benthamiana, with difference between cultivars; Chinese cabbage cv. Norang was not infected by any isolate, whereas cv. Chusarang was infected by all. Isolates GJS1, DJ1, DJ6, and mild isolate K1H2 were unable to infect radish cultivar Iljin, but no specific residues could be associated with avirulence in this host.