# Identification and Biological Features of Sesame Phyllody-Associated Phytoplasmas in Western Iran

## TL;DR

This study identifies two types of phytoplasmas causing sesame phyllody disease in Western Iran and suggests breeding resistant varieties for management.

## Contribution

The study reports the coexistence of two phytoplasma strains in sesame and their potential impact on disease severity.

## Key findings

- Two phytoplasma strains, 'Ca. Phytoplasma australasiaticum' and 'Ca. P. phoenicium', were identified in sesame samples.
- The phytoplasmas were transmitted to periwinkle plants via dodder, confirming their biological characteristics.
- The coexistence of the two strains may explain differences in disease severity observed in the field.

## Abstract

Sesame is an oilseed crop threatened by a phyllody disease associated with the presence of phytoplasmas, which can reduce yields by up to 80%. The molecular identification of these bacteria in crops located in Western Iran was achieved from samples showing symptoms of diverse intensity and types. For biological characterization, the pathogen was also dodder-transmitted to periwinkle plants. After nucleic acid extraction and nested PCR using phytoplasma-specific primer pairs amplifying part of the 16S rRNA gene, it was possible to amplify DNA fragments from both symptomatic sesame samples and dodder-inoculated periwinkle plants. The virtual RFLP pattern from the 16S rRNA gene sequences using iPhyClassifier indicated the presence of phytoplasma strains in 16SrII-D and 16SrIX-C subgroups. The identity percentage values of the obtained amplified sequences corroborated by the phylogenetic analysis identified them as ‘Candidatus Phytoplasma australasiaticum’ and ‘Ca. P. phoenicium’, respectively. The two phytoplasma strains were detected in different sesame samples collected in the same field. The coexistence of two phytoplasmas may influence the observed differences in disease severity and suggests appropriate management strategies, since diverse insect vectors were reported alongside diverse phytoplasmas associated with this disease. Moreover, the widespread disease presence strongly suggests the breeding of resistant varieties.