اولین گزارش از وقوع بیماری لکه نواری باکتریایی گندم در استان خوزستان

Xanthomonas translucens, the causal agent of wheat bacterial leaf streak disease, is recognized as one of the major wheat pathogens in the world and Iran. As a result, the seeds are wrinkled and their quality is reduced. BLS of wheat, has been reported from different regions of Iran including Sistan-o-Baluchestan, Kerman and Golestan provinces. During the spring of 2018, in wheat fields of Khuzestan province, such as Shush and Andimeshk Counties, leaf samples of the wheat plant with symptoms like water soak, narrow and elongated spots observed, collected and transferred to the laboratory for further studies. The infected tissues surface sterilization in 0.5% sodium hypochlorite for 30 seconds and rinsed three times using sterile distilled water. Pieces of tissues were crushed in some sterile distilled water and a loopful of the resulting suspension was spread on YPGA medium, and after 48hours, yellow, prominent and clear colonies appeared on the culture medium. The isolates were Gram-negative, yellow, levan positive, oxidase negative and catalase-positive and had yellow lipopolysaccharide colonies on YDC medium. In pathogenicity test on wheat, specific symptoms of the disease including water soak, narrow spots were observed, which became dead and brown at the center of the spots. Depending on the results of biochemical tests and pathogenicity, one of the isolates was selected as representative isolate to ensure the results, and the genomic DNA extracted by boiling was amplified by universal primer 16S rRNA gene and sequenced by Bioneer company of South Korea. Sequencing and BLASTing performed using NCBI gene bank. The studied isolate showed 98% homology with standard isolate X. translucens XT 2 (with GenBank accession number NR 036968). Phylogenetic analysis of the isolates recovered in this study and type isolates using a maximum likelihood algorithm indicated that it belongs to the same species. To our knowledge, this is the first report of wheat bacterial leaf streak caused by X. translucens in Khuzestan province.