Identification of 17 ‘Candidatus Phytoplasma pyri’ genotypes based on the diversity of the imp gene sequence

Abstract

Phytoplasmas of the apple proliferation group cause diseases in various fruit trees, mainly apples, pears and apricots. Immunodominant membrane protein, or ‘Imp’, shows high inter‐ and intraspecies gene variability, and is thus frequently used for population studies in these organisms. In this investigation, a survey was carried out of ‘Candidatus Phytoplasma pyri’ imp gene diversity in the Czech Republic. In total, 12 imp genotypes that could be clustered into nine groups were identified. Using all publicly available data, 17 distinct imp genotypes (labelled A–K) were defined. Interestingly, genotypes C, H and I were more related to ‘Ca. Phytoplasma mali’ than to other ‘Ca. Phytoplasma pyri’ imp genotypes, indicating that some strains may represent a transitional type between the two species. As Imp probably plays an important role in host–pathogen interactions, description of its diversity in ‘Ca. Phytoplasma pyri’ may help in understanding the epidemiology, symptomatology, and other aspects of pear decline disease. A simple RFLP PCR system is presented for rapid and cost‐effective discrimination of ‘Ca. Phytoplasma pyri’ imp genotypes.