شناسایی و بررسی تنوع ژنتیکی جدایه‌های عامل نواری باکتریایی گندم در استان های خراسان

Bacterial leaf streak (BLS) is an important disease of wheat (Triticum aestivum) worldwide caused by Xanthomonas translucens. Typical symptoms of leaf streak consist of elongated and light brown lesions which these lesions are water-soaked and translucent. During the 2017-1018, elongated, water-soaked and translucent lesions on wheat were observed in Khorasan provinces. The symptomatic samples were collected and the disease causative bacterium was isolated on sucrose nutrient agar )NAS( medium. The isolated colonies from plants were circular, mucoid and yellowish. All isolates were Gram-negative and produced xanthomonadin pigment in YDC medium. Pathogenicity of the isolates were confirmed after inoculation of wheat leaves (cv. Falat) by bacterial suspensions (1×107 CFU/ml) under greenhouse condition. Water-soaked lesions were started to develop 5 days after inoculation and the bacterial strains were reisolated from the symptomatic leaves 18 days post inoculation. Genomic DNA of the isolates were extracted and a fragment of the gyrB gene of the representative isolates were amplified with PCR and sequenced. The nucleotide sequences were compared with those deposited in GenBank by the BLAST program. Sequence compression indicated that the isolates have the highest identity (99% similarity) with Xanthomonas translucens pv. undulosa. Also, genetic diversity of 35 isolates was evaluated by rep-PCR using BOXA1R and ERIC1R, ERIC2 primers. Cluster analysis was done by the NTSYS program. For data analysis, the Jaccard coefficient and unweighted pair group method of arithmetic averages (UPGMA) were used. A relatively moderate level of genetic diversity was observed between isolates causing bacterial leaf streak of wheat in Khorasan provinces. Due to the spread of this disease in different parts of the country, application of different strategies in order to control this disease are necessary and needs more attention.