Phytoplasma-plant-vector relationships

Phytoplasmas are non-culturable mollicutes associated with diseases in many wild and cultivated plant species belonging to many different families. They are transmitted by phloem-sucking leaf and plant hoppers and psyllids and often cause economically important epidemics worldwide. This review focuses on their interactions with plant and insect hosts. Localization, concentration and movement of phytoplasmas in both hosts are considered, with special regard to organ colonization, multiplication, alteration of plant metabolism and insect fitness. The mechanisms and factors affecting insect transmission are presented. Phytoplasma genes possibly involved in host interactions are reviewed. The relevance of phytoplasma-plant-insect relationships in the epidemiology of phytoplasma-associated diseases is discussed.