جداسازی و بررسی تنوع فنوتیپی و ژنوتیپی عامل لکه نواری باکتریایی گندم در استان چهارمحال و بختیاری

One of the destructive diseases of wheat is bacterial leaf streak (BLS) caused by Xanthomonas translucens. In recent years, symptoms similar to the BLS disease have been observed in the wheat fields of some districts in Chaharmahal-o-Bakhtiari province. So, the present study was conducted for isolation and identification of the leaf streak agent in these fields. The phenotypic traits and genetic variation of the isolates were also investigated. In 2021 and 2022, from April to June, the field were visited and the samples with suspected symptoms of BLS were collected. ‌Isolation and purification of bacteria were performed according to the usual methods. The isolates were subjected to phenotypic tests. The pathogenicity test was done by foliar spraying and leaf injection of bacterial suspension (OD600=0.25) in five or six-leaf stage wheat plants. The plants were kept under plastic cover for two days and at a relatively high humidity. They were checked for symptoms appearance for two weeks. Bacterial re-isolation was successfully accomplished from infected plants. The genetic diversity of isolates was investigated by rep-PCR method using ERIC and BOX primers. In all tests, X. translucens isolate from Hamedan was also used. Based on the results, 19 isolates of X. translucens were successfully isolated from the sampled areas. The isolates were gram negative, aerobic, catalase positive and oxidase negative. They produced yellow pigment on YDC (Yeast extract-dextrose-CaCO3) medium. They showed positive reaction in 5% NaCl tolerance and growth at 40°C tests and negative reaction in Indole production, acid production from mannitol and potato soft rot tests. The isolates were different in some phenotypic characters such as gelatin and starch hydrolysis, acid production from maltose and sorbitol, hypersensitive reaction (HR) and lecithinase. rep-PCR showed the similarity of Chaharmahal-o-Bakhtiari isolates and Hamadan isolate, which may indicate their same origin. In general, not much genetic diversity was observed between the isolates. By combination the data obtained from BOX-PCR and ERIC-PCR, the isolates were divided into two main groups at the similarity of 70% and each group was divided into subgroups. The clusters did not have a particular match with the geographical origin of the isolates. The results of the present research confirmed the presence of X. translucens as the causal agent of wheat leaf streak in Chaharmahal-o-Bakhniari province.