Leek yellow stripe virus newly reported in Turkey

Leek (Allium porrum) is the second most important leafy vegetable grown in Turkey and 320,000 metric tonnes are produced annually. More than 20% of national production is grown in the Marmora region in north-west Turkey, in particular in the Bursa province. During field inspections in winter 2007, mosaic, yellow stripe, malformation and dwarfing symptoms (Fig.1) resembling those induced by Leek yellow stripe virus (LYSV) were observed in leeks grown in the Marmora region. Symptoms were observed in most of the fields surveyed. On average disease incidence was between 30-40% but in some fields disease incidence reached 90%.

A total of 42 samples were collected from leeks grown in the Canakkale, Bursa and Balikesir provinces in the Marmora region and tested for the presence of LYSV by DAS-ELISA using a polyclonal antibody (PAb) (Bioreba, Switzerland). The ELISA revealed that 39 of the 42 samples were infected with LYSV. The DAS-ELISA results were confirmed by detection of the 34 kDa LYSV coat protein in leaves of three infected leek plants using a Western blot assay with the same PAb. For further confirmation, viral RNA was isolated from four of the samples using a direct tube binding method (Suehiro et al., 2005) and tested for LYSV by RT-PCR (Dovas et al., 2001). No amplification was observed in the healthy and template controls but a 300 bp fragment was amplified from all symptomatic leek samples tested (Fig. 2). The amplicon was sequenced (GenBank Accession No. FJ358732) and had 93% nucleotide identity with the coat protein gene of a LYSV isolate from Argentina (AY007693), confirming the diagnosis of LYSV. To our knowledge, this is the first report of LYSV in Turkey. Although disease was detected only in the Marmora region in this study, similar symptoms have been observed in leek grown in other regions and field surveys are underway for LYSV in these regions. The existence of the aphid vectors of LYSV in leek-producing regions increases the prevalence of the disease and the potential for the virus to spread to other regions of Turkey.