Occurrence of palm rots disease caused by Citrobacter koseri,a new plant pathogen

Background and Aim : Date palm (Phoenix dactylifera) is one of the most important gardenproducts in the country. Khuzestan province considers as a main producing province of date fruit.Date palm offshoot rot symptoms include yellowing and finally drying of leaves, rotting andbrowning of lower parts of the diseased offshoots. The objective of the present study wasidentification of the causal agent of date palm offshoot rot in Khuzestan province.Methods : Ten symptomatic samples were collected from affected palm groves of Ahvaz, Abadan,Khorramshahr, Hamidiyeh, Shadegan, and Karun during ۲۰۱۹-۲۰۲۱. After superficial sterilization,the pieces were rinsed three times with sterile water and squashed using a sterile mortar and pestle,and then cultured on EMB medium. Common phenotypic tests were performed and MultilocusSequence Analysis (MLSA) was conducted.Results : A total of ۲۰ strains with metallic green colonies were isolated appeared after ۴۸hincubation at ۲۸ºC. Pathogenicity of ۱۲ strains was approved by inoculating petioles and rachisesof young two- or three-years date palms cv. Estameran. Pathogenic strains caused soft rot andbrowning of inoculated site while negative control remained symptomless. The obtained strainswere Gram and oxidase negative while they were catalase positive. Strains were negative in starchhydrolysis. All strains rot potato liquefy gelatin and arginine dihydrolase were positive. Strainswere able to growth on ۴% NaCl. The MLSA phylogenic tree based on the concatenated partialsequences of three housekeeping genes including gyrB, fusA and pyrG revealed that tworepresentative strains, PA۶۵ and PA۱۷۴ strains clustered with Citrobacter koseri LMG۵۵۱۹T with۱۰۰% bootstrap.Conclusion : Partial sequencing of the three housekeeping genes, gyrB, fusA, and pyrG genes wasused as a phylogenetic marker for determination of the phylogenetic relationships of the speciesof Citrobacter and the results revealed these genes could clearly demonstrate the taxonomy ofCitrobacter. C. koseri considered as an opportunistic pathogen in human. To the best of ourknowledge, this if first report of C. koseri as a plant pathogen.

کلیدواژه ها:

Common human and plant pathogen ، Emerging pathogens ، MLSA ، Phoenixdactylifera ، Iran.