First report of Cucurbit aphid-borne yellows virus in Vicia faba

There are 17 formally recognised virus species in the genus Polerovirus (family Luteoviridae) according to the ICTV classification released in 2014. Three polerovirus species have been described that affect production in economically important cucurbit crops: Cucurbit aphid-borne yellows virus (CABYV), Melon aphid-borne yellows virus (MABYV) and Suakwa aphid-borne yellows virus (SABYV). Two other poleroviruses, Beet western yellows virus (BWYV) and Pepper vein yellows virus (PVYV) have been detected recently in field-grown pepper plants in Turkey (Buzkan et al., 2013). During surveys in March 2016, symptoms including chlorosis of young leaves and yellowing of older leaves, suggestive of polerovirus infection, were observed in broad bean (Vicia faba) plants (Fig. 1) in Tarsus, a province in the Mediterranean region of Turkey.

A total of 36 diseased plants were tested for the presence of poleroviruses using DAS-ELISA (Dombrovsky et al., 2010) and 26 tested positive. A 1.1 kb portion of the polerovirus genome was amplified from all 26 ELISA-positive samples using the general polerovirus primer pair Pol-G-F and Pol-G-R in RT-PCR (Knierim et al., 2010). PCR amplicons were subsequently sequenced (GenBank Accession No. KY112798) and subject to a BLASTn search to identify the polerovirus species. According to an alignment of 473 nucleotides of the RdRp, the broad bean isolate showed 98% nucleotide identity with a CABYV isolate from cucumber from Iran (KF425567). To the best of our knowledge this is the first report of CABYV in V. faba in Turkey and globally. CABYV has been reported previously in a range of cucurbit crops in Turkey using DAS-ELISA (Yardımcı & Özgönen, 2007). However, the virus species was not confirmed since the CABYV polyclonal antibody used cross-reacts with other poleroviruses (Dombrovsky et al., 2010).

Since CABYV was first identified in 1992, the virus has been detected worldwide in temperate and subtropical areas (Lecoq et al., 1992). Apart from cucurbit crops, other species of agronomic importance that are CABYV hosts include Beta vulgaris and Lactuca sativa, as well as common weed species such as Capsella bursa-pastoris, Papaver rhoeas and Senecio vulgaris which are thought to be virus reservoirs (Knierim et al., 2010; Mnari-Hattab et al., 2009). CABYV is a phloem-limited virus that is transmitted in a persistent, non-propagative mode by aphids, including Aphis gossypii and Myzus persicae (Lecoq et al., 1992). Mixed polerovirus infections increase the risk of the emergence of recombinant viruses. Poleroviruses must be considered as important emerging pathogens in open-field and greenhouse vegetable cultivation.