Determination of new citrus Tristeza virus isolates in the Eastern Mediterranean region, and molecular characterization of these isolates

This study was carried out to determine the occurrence of new isolates of the Citrus tristeza virus (CTV) in the eastern Mediterranean region of Turkey, specifically in Adana, Mersin and Hatay provinces. 75 samples from 11 citrus orchards in which were observed symptoms of CTV were collected. Orange, grapefruit, mandarin, kumquat and calamondin most grafted on sour orange were present at the orchards. For the samples' molecular characterization, the RT-PCR test was applied using the CTV-CPU primers. 8 of the amplified samples showed positive results for CTV. These samples were designated as CTV-T1, CTV-T2, CTV-T3, and CTV-T4 and came from Karatas and Mersin orchards. The results revealed that the samples had an identity of 96-99% between our isolates and the Turkish isolates found in the GenBank databases. All our samples were grouped within the first clade together with the isolated T525 from California, which has been previously reported as containing mild and severe genotypes T30 and T36 respectively (Wang et. al. 2013). Additionally, Turkish isolates showed closeness with isolates from the eastern part of the Adriatic region (Bosnia, Croatia, Montenegro, and Serbia) which are closely related to New Zealand isolates that have been reported broken resistance in Poncirus trifoliata. This study confirms reports previously made by Cevik et al 2013, which suggest that Turkish isolates are a mixture of severe and mild strains of CTV. These data can be useful for the application of cross-protection programs and to avoid futures CTV epidemics in regions where rootstocks such as P. trifoliata are used.