Ligustrum witches broom phytoplasma caused witches' broom disease for Juniperus excelsa Bieb. in Turkey

In summer 2018, extensive phytosanitary checks occurred in Tufanbeyli, Adana, Turkey, in a vast forest. These were prompted by significant juniper tree losses with unusual shoot growth and witches' broom appearance. To investigate the presence of phytoplasma in the affected juniper trees, nested-PCR assays were employed. Universal phytoplasma-specific primer pairs were used for amplification of the 16S rRNA gene. A total of 300 samples were collected, comprising 242 samples from the witches' brooms displaying symptoms and 58 samples from apparently healthy trees. PCR results showed 90.5% of symptomatic juniper trees tested positive for phytoplasma. All asymptomatic junipers, except three trees, tested negative for phytoplasma in PCR analysis. The nucleotide sequences of 107 PCR amplicons derived from the infected samples were analyzed, revealing a high degree of similarity, ranging from 99.1 to 99.3%, to the 16S ribosomal DNA (rDNA) sequence of Ligustrum witches' broom phytoplasma (LiWBP). It is worth noting that this phytoplasma has been previously documented to infect California privet (Ligustrum ovalifolium) and maize (Zea mays L.) plants in Turkey. Phylogenetic analysis of 16S rDNA identified separate LiWBP strains from Ligustrum, maize, and juniper, forming a distinct clade. This underscores their unique evolutionary lineage and genetic divergence from other known phytoplasma groups. BLAST and in-silico RFLP analysis suggest the presence of a new subgroup or lineage specific to juniper within the LiWBP-related strains. This study unveiled an emerging witches' broom disease in juniper, attributing it to the Ligustrum witches' broom phytoplasma (LiWBP) and a newly discovered subgroup lineage.

Automated summary

A study in Tufanbeyli, Adana, Turkey revealed an emerging witches' broom disease in juniper trees, caused by the Ligustrum witches' broom phytoplasma (LiWBP) and a newly discovered subgroup lineage. PCR analysis showed a high percentage of infected juniper trees and their nucleotide sequences showed a high degree of similarity to LiWBP. This study highlighted the unique evolutionary lineage and genetic divergence of this phytoplasma.