Citrus species are among the three top fruit trees in the United Arab Emirates (UAE), with a combined total pro- duction of 12230 tons in 2011. Leaf samples were collected from four lemon (Citrus lemon L.) and five sweet orange (C. sinensis (L.) Osbeck) groves located in Al-Ain (south east of Abu Dhabi, UAE). Sampled trees showed weakened growth, but no typical symptoms of viroids and were tested for the presence of viroids by multiplex RT-PCR using two sets of primers specific for Citrus exocortis viroid (CEVd) and Cit- rus bent leaf viroid (CBLVd) (Al-Harthi et al., 2013). Testing disclosed the association of CEVd with 15 of 16 lemons in four groves, and with 18 of 18 sweet oranges in five groves. CBLVd was detected in six of 16 lemons in three groves and in five of 18 sweet oranges in three groves. To sequence PCR products, simplex RT-PCR was carried out with each primer set and two positive samples for CEVd and two for CBLVd. Amplifications produced fragments of the expected size, 371 bp for CEVd and 234 bp for CBLVd. PCR products were pu- rified and sequenced by Macrogen (Korea). CEVd sequences from the UAE were identical to each other and shared 99% nucleotide similarity to CEVd isolate CEVd-XNM-XY (Gen- Bank accession No. DQ431993), while the CBLVd sequence was identical to that of CBLVd isolate 201-1-2 Uy (accession No. AF428053). Sequences of both viroids from the UAE were deposited in GenBank (accession No. pending) This is the first record of CBLVd in the UAE. Presence of citrus viroids in Al-Ain, the most important agricultural area in the UAE, necessitates a larger scale study to characterize their distribution, pathogenicity and economic impact.
ASJC Scopus subject areas
- Plant Science