Genetic characterization of Iris yellow spot virus on onion (Allium cepa) and pathogenicity of two IYSV strains on onion and leaf onion (A. schoenoprasum).

Abstract

Iris yellow spot virus (IYSV) was isolated from onion with streaks on leaves in Saga and Chiba prefectures, Japan. Phylogenetic analysis based on the amino acid sequence identities of the nucleocapsid genes showed the presence of two strains, as represented by an isolate from onion in Brazil (IYSVBR) and that from Dutch iris (Iris hollandica) in the Netherlands (IYSVNL), on onion in Japan. Pathogenicity was tested on 11 cultivars of onion and five of leaf onion by mechanical inoculation with either of the two IYSV isolates, which were genetically similar with IYSVBR and IYSVNL, respectively. Both isolates caused the same type of streaks only on inoculated leaves of all onion cultivars tested, and the virus was not detected in upper leaves. None of the leaf onions developed symptoms on either inoculated or upper leaves, even though IYSV was detected in the inoculated leaves. Onion thrips (Thrips tabaci) transmission to onion, leaf onion, wakegi (Allium wakegi) and shallot (Allium grayi) was examined, and IYSV was detected from onion leaves where thrips fed. Bunyaviridae [03506]: Negative Sense ssRNA Viruses, Viruses, Microorganisms; Iridaceae [25325]: Monocotyledones, Angiospermae, Spermatophyta, Plantae; Liliaceae [25345]: Monocotyledones, Angiospermae, Spermatophyta, Plantae; Thysanoptera [75350]: Insecta, Arthropoda, Invertebrata, Animalia Iris yellow spot virus: pathogen; Iris hollandica [Dutch iris]: host, ornamental crop; Allium cepa [onion]: host, vegetable crop; Allium wakegi [wakegi]: host, vegetable crop; Allium grayi [shallot]: vegetable crop; Allium schoenoprasum [leaf onion]: host, vegetable crop; Thrips tabaci [onion thrips]: pest Microorganisms, Negative Sense Single-Stranded RNA Viruses, Viruses; Angiosperms, Monocots, Plants, Spermatophytes, Vascular Plants; Angiosperms, Monocots, Plants, Spermatophytes, Vascular Plants; Animals, Arthropods, Insects, Invertebrates leaf yellow spot: fungal disease, viral disease Brazil, South America, Neotropical region; Japan, Asia, Palearctic region; Netherlands, Europe, Palearctic region Iris yellow spot virus nucleocapsid gene [Bunyaviridae] pathogenicity; genetic characterization 20050920 Bunyaviridae [03506]; Iridaceae [25325]; Liliaceae [25345]; Thysanoptera [75350] 03502, Genetics - General; 03504, Genetics - Plant; 03506, Genetics - Animal; 31500, Genetics of bacteria and viruses; 33502, Virology - General and methods; 36006, Medical and clinical microbiology - Virology; 36008, Medical and clini…