Abstract
Tomato yellows disease (TYD) is a serious problem in tomato crops worldwide, in which two criniviruses are implicated: Tomato infectious chlorosis virus (TICV) and Tomato chlorosis virus (ToCV). During the growing season 2014-2015, survey of tomato-growing greenhouses conducted in different geographical locations of Riyadh region in Saudi Arabia in order to identify the criniviruses implicated in TYD. In total, 228 leaf samples were collected from tomato plants showing typical TYD symptoms, as well as 98 from other symptomatic crops and 283 arable weeds belonging to 38 species in 22 different families. Nucleic acids extracts prepared from the samples were tested by nested RT-PCR for the simultaneous detection of TICV and ToCV. In addition, 34 adult whiteflies were collected from the surveyed tomato greenhouses and analyzed using real time PCR. Results revealed that ToCV was the only virus associated with TYD as detected in 328 (53%) of a total of 609 tested samples (including all hosts tested), while it showed an expanded host range, as it was reported for the first time in bean, bitter gourd, eggplant and pepper in Saudi Arabia. In addition, ToCV was detected in 14 weed species belonging to 8 families. TICV was not detected in any of the tested samples. All collected whiteflies were identified as Bemisia tabaci biotype B (MEAM1), an efficient vector of ToCV. Sequencing analysis of 40 selected sequences of ToCV from different hosts clustered Saudi Arabian isolates into two subgroups. Almost all Saudi Arabian isolates shared high nucleotide identity among themselves (98.0-100%) while 97.1-100% with those published in NCBI.