Artichoke yellow ringspot virus as the causal agent of a new viral disease of lettuce: Epidemiology and molecular variability

Abstract

AbstractIn 2015 and 2016, lettuce (Lactuca sativa) plants showing yellow ringspots and line patterns were observed in Argolida (Peloponnese, Greece). Symptoms resembled those caused by nepoviruses, especially artichoke yellow ringspot virus (AYRSV), an endemic virus in artichoke (Cynara scolymus) and onion (Allium cepa var. cepa) crops in this area. The aim of this work was to identify and characterize the viral agent associated with the observed disease. We carried out mechanical inoculations onto Nicotiana benthamiana and lettuce plants and also virus‐specific reverse transcription (RT)‐PCR. Results confirmed the presence of AYRSV in all lettuce plants with symptoms tested, and the natural and experimental host range of the virus was studied. The species Heliotropium europaeum, Solanum nigrum, Origanum vulgare, Lactuca seriola, and Sinapis arvensis, are recorded as hosts of AYRSV for the first time. Also, AYRSV was detected by RT‐PCR in seeds and in the produced seedlings of lettuce, N. benthamiana, N. glutinosa, N. tabacum, and S. nigrum. Sequencing of a partial fragment of the gene encoding the RNA‐dependent RNA polymerase was performed for 29 isolates of AYRSV originating from different hosts (lettuce, artichoke, onion, and arable weeds). Phylogenetic analysis of AYRSV isolates classified them in diverse clusters that exhibited no host grouping. All groups included isolates from cultivated and wild plant species. In this study, AYRSV was associated with a new lettuce disease for the first time, thus increasing the known natural host range of the virus.