Abstract
In recent years, the decline of Brant’s oak, the main and most important tree of Zagros, is widespread. Considering the importance of oak trees, this study aims to identify the causal agent of the oak decline. Eight bacterial strains were isolated from infected tissues of oak trees, and these eight isolates have been identified by phenotypic characteristics. Three of eight isolates induced typical hypersensitive reactions on tobacco leaves, suggesting that they were pathogenic. Also, they were characterized as circular, gram-negative, facultatively anaerobic, oxidase negative, and catalase positive. The phenotypic and biochemical tests suggested that they belonged to the genus Entrobacter spp. One isolate (isolate Q1) exhibited amplification by PCR and was selected for the 16S rRNA gene sequence. The sequencing and phylogenetic analysis of this isolate showed ≥ 93% similarity to the Enterobacter cloacae complex. While a combination of biochemical and physiological characteristics in combination with DNA sequence analysis revealed that the isolate Q1 is Lelliottia nimipressuralis. Pathogenicity test and Koch’s postulates on the healthy seedlings and observing the symptoms confirmed that the isolate Q1 was the causal agent of the wetwood disease on Quercus brantii. This is the first report of oak dieback caused by Lelliottia nimipressuralis in Iran.