شناسایی عامل بیماری موزاییک ختمی چینی در استان خوزستان

China rose (Hibiscus rosa-sinensis L.) is a tropical and subtropical perennial plant from the family Malvaceae which is widely cultivated as an ornamental plant in the landscapes of Khuzestan province, southwest Iran. During 2015-2017, leaf mosaic and deformation symptoms were observed on China rose shrubs. In order to identify the causal agent of the disease, plant tissues were collected from symptomatic shrubs in different cities including Abadan, Ahvaz, Mollasani, Shushtar and Dezful. The mechanical transmission of the causal agent of the disease was carried out by rubbing the plant sap of symptomatic tissue onto 15 indicator plant species belonging to 4 families including Solanaceae, Amaranthaceae, Cucurbitaceae and Fabaceae. Local lesions were developed on Nicotiana glutinosa, Chenopodium quinoa, C. amaranthicolor and C. murale plants 1-3 days post inoculation (dpi). The plant species including Datura stramonium, Physalis alkekengi, Glycine max and Phaseolus vulgaris showed systemic chlorosis while Solanum lycopersicum, N. tabacum var. Turkish, S. melongena and Capsicum annum displayed systemic mosaic 14-18 dpi. Indicator plants from the family Cucurbitaceae did not show any visible symptom till 30 dpi. Indirect-ELISA using polyclonal antibody of Tobacco mosaic virus (TMV) was performed and the plant samples collected from symptomatic China rose shrubs exhibited positive reaction. ELISA-positive samples were then subjected to polymerase chain reaction (PCR) using specific primers of Tomato mosaic virus (ToMV) which resulted in the amplification of coat protein (CP) gene (~620 bp) of the viral genome. Four isolates of ToMV were selected for Sanger sequencing of the amplified DNA fragments. Nucleotide comparison of the resulting sequences with that of other ToMV isolates previously deposited in GenBank showed 96-98% identity. The four ToMV isolates were then submitted to GenBank under the accession numbers of MH230112, MH230113, MH299883 and MH299884. Phylogenetic analysis of nucleotide and amino acid sequence of ToMV isolates originating from various sources and different geographical locations was carried out using CLC Main Workbench software (ver. 7.6.2) and the phylogenetic trees were constructed based on Maximum Likelihood algorithm with 1000 bootstrap values. Phylogenetic trees demonstrated similar topologies according to which ToMV isolates were classified into two clades; Clade I and Clade II. ToMV isolates obtained in this study were placed in Clade I and formed a separate cluster within this clade. The results showed that ToMV is responsible for leaf mosaic and deformation of China rose shrubs in Khuzestan province.