Hazelnut (Corylus avellanae), a plant native to the temperate northern hemisphere, is cultivated in Iran mainly in the northern parts of the country. Irregular reddish-brown necrotic spots surrounded by a yellow halo on hazelnut leaves and fruit bracts, leading to wilting of leaves, defoliation, and branch dieback, were observed during 2018 and 2019 in hazelnut orchards of the Guilan province. Isolation from symptomatic tissues on nutrient agar (NA) medium yielded bacterial colonies, the predominant types of which were selected for characterization. Isolates selected were Gram negative, produced a fluorescent pigment on King’s medium B and a hypersensitive reaction on tobacco. Thirty-five isolates belong to LOPAT group Ia (+ - - - - +) sensu Lelliott et al. (1966) and positive for gelatin liquefaction and aesculin hydrolysis but negative for tyrosinase activity and tartrate utilization (G⁺A⁺T⁻Ta⁻). The isolates proved to be pathogenic on hazelnut cv. Alamut. Phylogenetic analyses based on partial sequences of the five protein-encoding housekeeping genes gyrB, rpoB, rpoD, gapA, and gltA of four pathogenic isolates selected, indicated that the representative isolates were identical to each other and formed a branch in the phylogram among other pathovars of Pseudomonas amygdali. Based on phenotypic and pathogenicity characteristics and phylogenetic affiliation, the bacterium inciting a not earlier described hazelnut disease, appears to be a novel pathovar of P. amygdali, for which here provisionally is named P. amygdali pv. corylicola. Formal description of the pathovar is in preparation.

榛子 ( Corylus avellanae)，一种原产于北半球温带的植物，主要​​在伊朗北部地区种植。2018年和2019年在桂兰省榛子园观察到榛子叶和果实苞片上出现不规则的红褐色坏死斑，周围有黄色晕圈，导致叶片萎蔫、落叶、枝干枯死。从营养琼脂 (NA) 培养基上的症状组织中分离产生细菌菌落，选择其主要类型进行表征。选择的分离株是革兰氏阴性菌，在 King's 培养基 B 上产生荧光色素，在烟草上产生过敏反应。35 个分离株属于 LOPAT 组 Ia (+ - - - - +) sensu Lelliott 等人。⁺ A ⁺ T ^- Ta ^- )。分离株被证明对榛子 cv 具有致病性。阿拉穆特。基于所选择的四个致病分离株的五个蛋白质编码管家基因gyrB、rpoB、rpoD、gapA和gltA的部分序列的系统发育分析表明，代表性分离株彼此相同，并在系统谱中形成一个分支。杏仁假单胞菌。基于表型和致病性特征以及系统发育关系，该细菌引发了一种未曾描述过的榛子病，似乎是一种新的致病菌P. amygdali，这里暂时命名为P. amygdali pv 。紫阳花。pathovar 的正式描述正在准备中。