Identification of Endophytic Microbiota of Phytoplasma-Infected Russian Olive Trees Elaeagnus angustifolia L. in the Northwest of Iran

In this study, Russian olive trees exhibiting witches'-broom symptoms were collected from urban green areas in Tabriz, in the northwest of Iran. PCR analysis confirmed that phytoplasma caused the disease and, according to the resulting Sanger sequencing electropherogram, a mixed infection with two or more phytoplasma species within the Russian olive trees was revealed. Next-generation sequencing analyses, using the Illumina method, were performed on total DNA from the infected Russian olive plants to recognize the microbial genomic content and assemble the whole genome of the causative pathogen(s). The use of MetaphlAn2 and Kraken2 to analyze species composition revealed the very diverse and unique compositions of different Prokaryotic and Eukaryotic species within the infected plants. Several bacteria and fungi were discovered inside the samples, among which Mycoplasmatota was significantly dominating. Interestingly, the results also revealed a high level of endosymbiotic bacteria and Archaea (Methanobacteria) genome contents within the samples. Bowtie2, metaSPAdes, and CD-HIT pipelines were used to perform the initial genome assembly, and the whole genome of the notable phytoplasma species was assembled and submitted to Genbank.

Automated summary

This study investigated Russian olive trees exhibiting witches'-broom symptoms in urban green areas in Tabriz, Iran. The disease was confirmed to be caused by phytoplasma, and a mixed infection with multiple phytoplasma species within the trees was revealed. Next-generation sequencing using the Illumina method was performed to analyze the microbial genomic content and assemble the whole genome of the causative pathogen(s). The analysis revealed diverse and unique compositions of prokaryotic and eukaryotic species within the infected plants.