First report of Plum pox virus on Tilia spp. in Turkey

Abstract

The Tilia genus (linden, lime) comprises about 30 deciduous tree species native to North America, Europe, and Asia. They are often used along roads and in parks because of their aesthetic value in urban landscapes. During surveys in 2017–2018 in Istanbul, Turkey, typical viral disease symptoms such as foliar mosaics, mottling and chlorotic ringspots, and deformations were observed on Tilia spp. (Figs. 1-3). Forty-six leaf samples were collected from diseased and asymptomatic trees from 43 different recreation fields in Istanbul. All leaf samples were screened for Plum pox virus (PPV) by DAS-ELISA (PPV ELISA kit, Bioreba, Switzerland). Three leaf samples had positive ELISA test results with mean absorbance values (A405) ranging from 0.73 to 0.74 compared to 0.21 in the healthy control. To confirm the presence of PPV, total RNA was extracted from the diseased and the healthy leaf samples using a Qiagen RNeasy Plant Mini kit and subjected to RT-PCR using universal primers P1/P2 located at the C-terminus of the PPV coat protein (CP) gene as described by Wetzel et al. (1991). A 243 bp product was amplified from the three ELISA positive samples, confirming infection with PPV. The amplicon from one sample was cloned and sequenced, and the partial sequence was deposited in GenBank (Accession No. MF616012). Analysis of the obtained sequence revealed that it shares the highest (100%) nucleotide identity with PPV isolate AnMrPl540 (MG686887.1) from Turkey, and the lowest identity (86%) with PPV isolate Avang (KU359729.1) from Russia. Phylogenetic analysis by the neighbour-joining method using MEGA7 software (Kumar et al., 2016) indicated the Turkish Tilia isolate clustered closely with isolate AnMrPl540 (MG686887.1) (Fig. 4). The disease caused by PPV, known as Sharka, is particularly detrimental to apricots, peaches, and European and Japanese plums because it can seriously reduce yield and fruit quality. Losses in susceptible cultivars may reach 100% in some cases (Kegler & Hartmann, 1998; Németh, 1994). It has also been reported to infect several ornamental and wild Prunus species as natural and experimental hosts (Damsteegt et al., 2007). This is the first report of PPV on Tilia sp. as a natural host in the world. Further molecular studies will be conducted to obtain the full genome sequence of the Tilia isolate and understand its phylogenetic relationship with other published PPV sequences.