Carlavirus isolates from cultivated Allium species represent three viruses

Abstract

From 12 cultivated and mostly vegetatively propagated Allium species and varieties tested for carlavirus infections, 94 virus isolates were obtained which varied greatly on indicator hosts. Chenopodium amaranticolor, C. quinoa, Celosia argentea vat. plumosa 'Geisha', Nicotiana hesperis accession 67A and N. occidentalis accession P1 proved valuable for detection, isolation and propagation of part of the isolates. The latter three species are new experimental hosts for carlaviruses of Allium species. Other isolates could only be transmitted to Allium species such as crow garlic (A. vineale) leek (A. ampeloprasum var. porrum) and onion (A. cepa var. cepa). The isolates were grouped into three viruses by differential hosts and host reactions and their reaction with four antisera.Shallot latent virus (SLV) was found in ever-ready onion (A. cepa var. perutile), grey shallot (unidentified Allium species), multiplier onion (A. cepa var. aggregatum), pearl onion (A. ampeloprasum var. sectivum), rakkyo (A. chinense), shallot (A. cepa var. ascalonicum), and Welsh onion (A. fistulosum). Virus isolates from garlic and Asian shallot, fully reacting with antiserum to SLV but differing in host reactions from the SLV typeisolate, are now described as garlic strain (SLV-G) and Asian shallot strain of the virus, respectively. The 'garlic latent virus' from garlic described in Japan is now considered identical with SLV-G.A carlavirus almost universal in garlic, and also found in great-headed garlic (A. ampeloprasum var. holmense), in an unidentified Allium species, and occasionally in leek, did not react with the antisera to SLV and the Japanese 'garlic latent virus', and is now described as the new garlic common latent virus (GCLV). It appeared identical to a virus erroneously identified in Germany as garlic latent virus.The new Sint-Jan's-onion latent virus (SjoLV) from Utrechtse Sint-Jan's onion (unidentified Allium species) from the Netherlands and similar crops originating from other countries, did not induce reactions in test plants and could only be detected by electron microscope decoration tests. It reacted equally well with the antisera to SLV and GCLV. It was also present together with SLV in ever-ready onion, pearl onion, rakkyo, shallot, and Welsh onion. 'Garlic latent virus' reported in Japan from hosts other than garlic should be regarded as SLV, SjoLV, or a mixture of these viruses.The carlaviruses were not detected in wild plants of ramsons (A. ursinum), and of the predominantly vegetatively propagated crow garlic (A. vineate), field garlic (A. oteraceum), and sand leek (A. scorodoprasum), collected in the Netherlands.Severe reactions in the indicator hosts incidentally revealed soil-borne viruses in shallot (the nepoviruses Arabis mosaic virus (ArMV) and tomato black ring virus) and crow garlic (ArMV and the tobravirus tobacco rattle virus). Tobacco necrosis virus (necrovirus) was detected in roots of shallot.

Incidence of Garlic common latent virus in Argentina, and phylogenetic and recombination analyses of isolates

“…Onion yellow dwarf virus and Leek yellow stripe virus, respectively, were reported by those authors in the main garlic-producing regions, with incidence percentages ranging from 33 to 100% and from 34 to 98%. These results disagree with those found in other works (Van Dijk, 1993;Tsuneyoshi et al, 1998;Klukácková et al, 2007), which indicated that GarCLV is the most common virus infecting garlic.…”

“…These differences could be due to different factors, such as resistance or tolerance of some garlic genotypes to GarCLV, or a lower aphid transmission efficiency of these viruses (Van Dijk, 1993). Considering that garlic is a species of exclusively agamic propagation, it is assumed that infected plants transmit the virus to successive generations, that the viruses will persist, and that the number of infected plants will increase gradually.…”

“…The carlaviruses present in Alliaceae were misidentified for a long time. Shallot latent virus (SLV) was originally detected in shallots and then in garlic by several authors (Bos et al, 1978;Van Dijk, 1993;Barg et al, 1994;Tsuneyoshi et al, 1998;Torrico et al, 2010), whereas Garlic latent virus (GLV) was found in garlic by Lee et al (1979). However, biological and genomic comparisons of SLV and GLV showed that both viruses were in fact the same species (Van Dijk, 1993;Tsuneyoshi et al, 1998).…”

“…Therefore, this carlavirus was shown to be different from CLV from carnation and was named Garlic common latent virus (GarCLV) (Van Dijk, 1993;Barg et al, 1994;Barg et al, 1997).…”

“…GarCLV was mentioned as one of the most frequent viruses affecting garlic crop (Van Dijk, 1993;Tsuneyoshi et al, 1998), being reported in several countries of Asia (Barg et al, 1994;Tsuneyoshi et al, 1998;Pramesh & Baranwal, 2013), Europe (Bellardi et al, 1995;Tsuneyoshi et al, 1998;Dovas et al, 2001;Dovas & Vovlas, 2003;Klukácková et al, 2007;Shahraeen et al, 2008), Oceania, North America (Pappu et al, 2005;Pérez-Moreno et al, 2007), and South America (Conci, 1997;Fajardo et al, 2001;Nieto et al, 2005). A study of GarCLV incidence conducted in Greece showed that infection rates were variable, with up to 97.6% of infected plants in the province of Arcadia (Dovas et al, 2001).…”