Stenotrophomonas sp. associated with leaf spot and leaf blight diseases of date palm in Iran

Leaf spot and leaf blight are the most important and new diseases of date palm in the world as well as Iran. This research was aimed to study the association of the bacteria with leaf spot and leaf blight diseases of date palm in Kerman province, Iran. For this purpose, during 2018-2019, date palm leaves showing leaf spot and blight symptoms were sampled from different areas of the province. Isolation of bacteria from the collected samples was performed according to the standard plant bacteriological method. Pathogenicity of the isolates was investigated by inoculation on midrib and leaflets of date palm ‘Mazafati’ cultivar using attached and detached leaves for several times. Selected bacteria isolates were identified by performing the key phenotypic bacteriological tests and nucleotide sequence analysis of a part of 16S rRNA gene after PCR assay. In this study, a total of 15 bacterial strains were isolated from the collected samples. Artificial inoculation tests showed that four isolates were able to cause mild leaf spot symptoms on date palm leaves. The results of phenotypic and molecular analysis revealed that the selected isolates were related to Stenotrophomonas sp. This is the first report on association of a bacterium with date palm leaf spot and leaf blight diseases in Iran and introduction of Stenotrophomonas sp. as an opportunistic pathogen on date palm in the world.