Phytoplasmas (genus Candidatus Phytoplasma) are wall-less bacteria from the class Mollicutes that affect numerous plant species worldwide causing significant economic losses. They have a unique life-style inhabiting plant phloem and insect cells and needing both hosts for survival in nature. Their genomes are repeat-rich yet relatively small and reduced missing many basic metabolic pathways. Phytoplasma axenic cultivation is still challenging. Nevertheless, 4 phytoplasma genomes have been sequenced and annotated with several genome drafts also available. However, the understanding of all mechanisms underlying phytoplasma pathogenicity is far from complete. First molecular evidence for the phytoplasma presence in Croatia has been given in late 1990’s on grapevine. Since then, the number of discovered phytoplasma species, insect vectors and affected plant hosts is rising with grapevine and fruit trees’ phytoplasma pathosystems being well characterized. The main objective of this project would be sequencing of ‘Ca. P. solani’, the most widespread phytoplasma in Croatia, with generation and comparative analysis of genome draft or fully assembled genome. Obtained results would give new data on candidate virulence effectors and other factors involved in interactions with hosts and adaptation to different environments. Another goal would be genotyping of new and already available isolates by multilocus sequence typing (MLST) analyses of house-keeping and specific variable genes. New genotyping tools for improved diagnostics and molecular epidemiology studies with implications in risk assessment would also be developed. Functional studies would focus on surface variable membrane proteins involved in interactions with insect hosts and transmissibility. Moreover, this would be the first sequencing project of a bacterial plant pathogen genome in Croatia. The establishment of this project would open a new field of molecular plant pathology and genomics in Croatian science.