خصوصصيات مولكولي و موقعيت تاكسونوميكي جدايه ايراني ويروس پيچيدگي برگ گوجه فرنگي TOMATO LEAF CARL VIRUS( )

MOLECULAR CHARACTERIZATION AND TAXONOMIC POSITION OF THE IRANIAN ISOLATE OF TOMATO LEAF CURL VIRUS

Tomato leaf curl virus (TLCV, Family Gemimiviridae, genus Degomovirus) is a whitefly (Bemisia tabaci) transmitted geminivirus (WTG) causing a destructive disease of tomato in many regions of India, East Asia and Australia. While TLCV isolates from Australia, Bangalore (India) and Taiwan and Tomato yellow leaf curl virus (TYLCV) isolates from different regions of Asia, Europe and America have a single genomic component (designated DNA A), those from Northern India and Thailand have two components (DNA A and DNA B). Previously, TYLCV-like geminiviruses have been identified from southern provinces of Iran causing leaf curling, stunting, and severe reduction in fruits of tomato plants in the fields. We have used degenerate DNA A specific PCR primers to clone part of the genome of an Iranian isolate of TLCV (TLCV-Ir) from field-infected tomato plants growing in Iranshahr, Sistan-Baluchestan Province. Degenerate DNA B-specific PCR primers did not amplify a putative DNA B from infected tomato under conditions that DNA B fragments were amplified from plants infected with Tomato golden mosaic virus, a known bipartite begomovirus. The full-length 2763 nucleotide DNA A genome of TLCV-lr was sequenced and compared to Iranian isolate of TYLCV (TYLCV-Ir, previously sequenced by Bananej et al., (GenBank accession No. AJ 132711) isolated from tomato in the same region.As other monopartite TLCV and TYLCV isolates, both TLCV-lr and TYLCV-lr genomes contain six open reading frames, two on the virion-sense strand and four on the complementary-sense strand. Sequence comparisons indicated that TLCV-lr is substantially different from TYLCV-lr with only 79°/o nucleotide sequence identity. Phylogenetic analysis showed while the TYLCV-lr represents an isolate of TYLCV-lsrael (TYLCV-ls) group, the TLCV-lr is closer to TLCV isolates from southern India (TLCVs-Bangalore 2-5) which are most similar to other WTGs infecting tomato and cotton in Pakistan, India and East Asia and differ substantially from T(Y)LCVs of the Middle East, America, Europe and Australia. Presence of two tomato - infecting begomoviruses in the same area provides a favorable environment for recombination of these viruses.