A bacterial disease of walnut (Juglans regia) has been observed in northwestern Iran during the summer of 2018 with symptoms similar to the shallow bark canker on trunks and branches. In the present study, two hundred and thirty-six obtained isolates were characterized and classified into three major groups based on the biochemical and physiological characters. With the species-specific primer pairs, Brenneria rubrifaciens was not detected, and a few isolates were recognized as B. nigrifluens. The partial 16S rDNA sequences and multilocus sequence analysis based on housekeeping genes gyrB, rpoB, infB, and atpD following a phylogenetic analysis revealed that the isolates are belonged to B. roseae subsp. roseae, B. nigrifluens and Gibbsiella quercinecans (190 out of 236 isolates) species. Iranian isolates formed the monophyletic clades and had high sequence similarity with the relative type strains. The pathogenicity tests of G. quercinecans, B. roseae subsp. roseae and B. nigrifluens isolates on branches and trunks of 5-year-old walnut trees indicated that they had effective potential to cause necrosis and canker on branches. The effective identification of potentially pathogenic bacterial species associated to the canker disease of walnut trees was confirmed using species-specific primer pairs and concatenated partial sequences of housekeeping genes. Further investigation is necessary to determine the agents might be involved in the etiology of the disease.

2018 年夏季在伊朗西北部观察到一种核桃细菌病（Juglans regia），其症状类似于树干和树枝上的浅树皮溃疡病。在本研究中，对 236 株分离株进行了表征，并根据生化和生理特征分为三大类。使用物种特异性引物对，未检测到红布氏菌，少数分离株被识别为黑火芽孢杆菌。基于管家基因gyrB、rpoB、infB和atpD的部分16S rDNA序列和多位点序列分析系统发育分析表明这些分离物属于B . 玫瑰亚种 roseae、B. nigrifluens和Gibbsiella quercinecans（236 个分离株中的 190 个）物种。伊朗分离株形成单系进化枝，与相关类型菌株具有高度的序列相似性。G. quercinecans , B的致病性试验。玫瑰亚种 蔷薇科和B. nigrifluens5 年生核桃树树枝和树干上的分离株表明，它们具有引起树枝坏死和溃疡病的有效潜力。使用物种特异性引物对和管家基因的连接部分序列证实了与核桃树溃疡病相关的潜在致病细菌物种的有效鉴定。需要进一步调查以确定可能与疾病病因有关的药物。