First Report of Carrot torrado virus 1 and Carrot thin leaf virus Naturally Infecting Torilis arvensis ssp. arvensis in Greece
MetadataShow full item record
Cita bibliográficaL. Lotos, A. Olmos, N. I. Katis, and V. I. Maliogka. First Report of Carrot torrado virus 1 and Carrot thin leaf virus Naturally Infecting Torilis arvensis ssp. arvensis in Greece.Plant Disease 2018 102:10, 2049-2049
Plants of the Apiaceae family are susceptible to many viruses. These viral infections cause yield reduction and leaf symptoms that affect product marketability. In Greece little is known about the number, spread, and importance of viruses infecting apiaceous plant species. During a survey investigating the presence of poleroviruses in different hosts, a wild Torilis arvensis ssp. arvensis plant (sample RL5) exhibiting leaf reddening symptoms was subjected to high-throughput sequencing of small RNAs, extracted with the mirPremier microRNA Isolation Kit (Sigma-Aldrich, St. Louis, MO) from leaves and stems, on an Ion Torrent platform. The run yielded 1,809,132 reads in the 21 to 24 nt range. De novo assembly of these reads and subsequent blast analysis (BLASTn/x) of the 2,512 contigs that were produced revealed, apart from a polerovirus-like sequence (data not shown), the presence of two additional viruses, Carrot thin leaf virus (CTLV, genus Potyvirus, family Potyviridae) and Carrot torrado virus 1 (CaTV1, genus Torradovirus, family Secoviridae). Blasting revealed that 129 de novo contigs from 40 to 255 nt in length were similar to CTLV, and 138 from 40 to 410 nt to CaTV1. The complete genome of CTLV (isolate RL5-Pot, accession no. LT615233) was reconstructed using iterative mapping of the 21- to 24-nt reads to the de novo contigs, with 233,894 reads mapped in total. Similarly, 38,545 reads produced the complete RNA2 of CaTV1 (isolate RL5-Tor, accession no. LT615234), and 9,508 reads the ≈85% of RNA1. Similarity analysis with the isolates deposited in the online databases (CTLV, JX156434 and JX156435; CaTV1, KF533719 and KF533720) showed 85.9% identities in nucleotides for CTLV-RL5-Pot and 77.3 and 94.7% identities in nucleotides for RNA1 (of the 85% that was reconstructed) and RNA2 of CaTV1-RL5-Tor, respectively. To detect these viruses in sample RL5, two sets of primers were designed, Tor3185-Up (5′-CTTTCCACCAATATTATGCAAGTTCC-3′) and Tor3854-Down (5′-ATAAAAAATCCACTCCGCTTCTTCC-3′) and Pot8068-Up (5′-GAAGTTCGGATGCTAGATGAGTTAC-3′) and Pot8820-Down (5′-GTTGAATTGGTTGTGTGTTGATCTTG-3′), which amplify 670 and 753 nt of CaTV1-RNA2 and CTLV, respectively. Reverse transcription polymerase chain reaction assays produced the expected amplicons for both viruses in sample RL5, and Sanger sequencing of the amplicons confirmed the sequence obtained by next-generation sequencing. Thirty-two additional samples from different cultivated and wild apiaceous plant species were screened for both viruses, and only one was found to be infected with CaTV1. The infected plant was a wild carrot (Daucus carota) (sample UmNp1) originating from a different location, ≈200 km away from the collection site of RL5. CaTV1 was originally identified by Adams et al. (2014) in the United Kingdom and in 2017 it was reported in France (Rozado-Aguirre et al. 2017). The virus has been previously detected in cultivated carrots; however, this is a first report from naturally infected wild hosts, which could potentially act as its reservoirs in the field. CTLV has been known for many years; however, its full sequence was only recently obtained by Xu et al. (2014). That study also revealed that CTLV can infect a number of different wild and cultivated species, but so far it has not been reported in T. arvensis. This is the first report of these two viruses in Greece, thus extending the information on their geographical distribution. Additional screenings are necessary to evaluate the presence and impact of CaTV1 and CTLV in Apiaceae crops in Greece.