Assessment of imp, aceF and secY as genotyping tools in MLST analysis of ‘Candidatus Phytoplasma mali’ 
M. SERUGA MUSIC (1), J. Plavec (2), I. Krizanac (2), Z. Budinscak (2) (1) Department of Biology, Faculty of Science, University of Zagreb, Croatia; (2) CCAFRA- Institute for Plant Protection, Croatia

Phloem-limited and uncultivable bacteria ‘Candidatus Phytoplasma mali’ is associated with apple proliferation (AP) disease that represents one of the major threats for European apple production. two psyllid species have been identified as insect vectors transmitting the disease exclusively on apple. The small genome of ‘Ca. P. mali’ has been sequenced revealing the unusual architecture of its linear chromosome. Moreover, the presence of great number of unique features, as well as those shared among phytoplasmas was shown, with an array of potential candidates to be used as common genotyping tools. In Croatia, recently ‘Ca. P. mali’ has been molecularly identified in both apple and insects. In this study, we assessed housekeeping aceF and secY, as well species-specific imp gene as genotyping tools in multilocus sequence typing (MLST) analysis of ‘Ca. P. mali’ strains from Croatia. New primers were designed for selected genes in order to amplify the entire sequence from nearly 70 apple and insect samples. Amplicons were sequenced and phylogenetic analysis was performed. The results revealed the presence of at least 6, 9 and 8 different genotypes for aceF, secY and imp gene, respectively, corroborating their value as genotyping tools for distinction among AP strains. Surprisingly, housekeeping gene secY exhibited more variability then AP-specific imp gene involved in interactions with insects, reflecting the evolution of this phytoplasma as a host-specific pathogen.

Abstract Number: P19-706
Session Type: Poster