Foveavirus , a new plant virus genus
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Virology Division News Arch Virol 143/6 (1998)
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Virology Division News
Foveavirus, a new plant virus genus G. P. Martelli1 and W. Jelkmann2 1
Dipartimento di Protezione delle Piante, Università degli Studi e Centro di Studio del CNR sui Virus e le Virosi delle Colture Mediterranee, Bari, Italy 2 Biologische Bundesanstalt für Land- und Forstwirtschaft, Institut für Pflanzenschutz im Obstbau, Dossenheim, Germany
Summary. Foveavirus is a novel genus of plant viruses with helically constructed filamentous particles ca. 800 nm long, typified by apple stem pitting virus (ASPV). Virions do not contain lipids or carbohydrates, have a positive sense, single-stranded, polyadenylated RNA genome 8.4 to 9.3 kb in size, and a single type of coat protein with a size of 28 to 44 kDa. The genome of definitive viral species is made up of five ORFs encoding respectively, the replication-related proteins (ORF 1), the putative movement proteins (ORF 2 to 4, constituting the triple block gene), and the coat protein (ORF 5). Virions accumulate in the cytoplasm, where replication is likely to occur with a strategy comparable to that of potexviruses, based on direct expression of the 5'-proximal ORF, and expression of downstream ORFs through subgenomic RNAs. No vector is known. Virus transmission is by grafting, and dispersal is through infected propagating material. The genome structure and organization (i.e. number and order of genes) closely resembles that of the genera Potexvirus, Carlavirus and Allexvirus, but ORF 1 and the coat protein cistron (ASPV only) are significantly larger. Introduction Apple stem pitting virus (ASPV) is widespread in commercial apple cultivars which are symptomlessly infected, unless they are grafted on sensitive rootstocks [18]. Symptoms consisting of pitting of the woody cylinder, or epinasty and decline, develop in some ornamental Malus species and in Virigina Crab and Spy 222 indicators. Moreover, a close relationship was reported between ASPV and the causal agent of necrotic spot and vein yellows diseases of pear [5, 7, 8, 17, 18]. The identity of the two agents was proven by back transmissions to apple and pear [10] and by comparative characterization of a large number of viral isolates from Europe [15]. A virus with filamentous flexuous particles ca. 800 nm long was transmitted by inoculation of sap from stem pitting-diseased apples to Nicotiana occidentalis, and partially characterized [9]. This virus appeared to differ from other known plant viruses and was tentatively assigned to subgroup A of the then extant Closterovirus group [1]. However the revision of the plant virus taxonomic system [11] led to the establishment of the genus
Virology Division News
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Closterovirus (now family Closteroviridae), from which viruses of subgroup A were separated to be assigned to either of two to new genera, Trichovirus and Vitivirus [12, 14]. ASPV was not assigned to any of these genera and was excluded from the 6th Report of the ICTV [14]. Meanwhile, molecular studies had provided detailed informa
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