First Report of Citrus tristeza virus in Citrus Orchards in Bosnia and Herzegovina.

Abstract

The citrus growing area in Bosnia and Herzegovina (B&H) is limited to the confluence of the river Neretva, which is close to the Adriatic coastal region. Approximately 6 ha are grown in the country. Mandarins (Citrus reticulata Blanco) and lemons (Citrus limon L.) grafted on trifoliate orange (Poncirus trifoliata (L.) Raf.) are the most cultivated species. In June 2012, 25 samples were collected from individual trees from three locations in Herzegovina district of B&H (Mostar, Čapljina, and Ljubuški). Samples of different Citrus spp. (C. reticulata Blanco, C. aurantium L., C. limon L., C. sinensis (L.) Osbeck, P. trifoliata (L.) Raf., and Fortunella margarita Lour) and varieties were collected from infield plants, commercial citrus orchards, and a nursery. Out of 25, 10 citrus trees exhibited leaves chlorosis, whereas as all others were apparently symptomless. Double antibody sandwich (DAS)-ELISA test, using commercial kit from the DSMZ, Germany (product code AS-0988), was carried out to confirm the presence of Citrus tristeza virus (CTV). In addition, further analyses were performed using reverse transcription (RT)-PCR targeting the coat protein gene (2). CTV was detected in 8 out of the 25 tested samples with DAS-ELISA, whereas CTV was detected in 14 samples by RT-PCR. Being grafted on P. trifoliata rootstock, no typical CTV symptoms in the field were observed on the CTV-infected trees; interestingly, the lab analyses evidenced the CTV presence in all inspected locations of the Herzegovina district. To our knowledge, this is the first report of CTV in Bosnia and Herzegovina; nevertheless, the virus presence is also reported from neighboring countries Croatia (1) and Montenegro (3). The PCR products of four samples were additionally analyzed by sequencing. The preliminary results by sequencing of the coat protein gene of four selected CTV isolates (Accessions HF947341, HF947342, HF947343, and HF947347) showed 99% nucleotide identity with the CTV resistance breaking isolates from Montenegro (FR871866) and Croatia (EU579422). Although a very small number of samples were tested in this study, CTV appears to be widely distributed in the citrus orchards of the country. This could be related to the traditional use of tolerant P. trifoliata rootstock that prevents the development of the tristeza decline as well as to the virus isolates present in the region, which appear not to cause another economically devastating CTV disease such as stem pitting. Further research will be dedicated to the biological properties of the genetic variability of these identified CTV isolates and the assessment of potential aphid vectors.