engleski

Investigating flavescence dorée phytoplasma emergence and the paths of spread by MLST in Croatia

Backgrounds Phytoplasmas are plant-pathogenic bacteria with a complex two-kingdom-host life cycle involving plants and insect vectors. Flavescence dorée (FD) phytoplasma is a quarantine pathogen associated with severe and epidemic grapevine yellows disease that represents great threat for grapevine cultivation in Europe. Objectives From the first report in Croatia (2009) for restricted continental area, FD phytoplasma has been detected in other winegrowing regions of the country with clear epidemic trend of the disease spread. The main objective of this study was to trace FD phytoplasma emergence, to study the prevalence and distribution of FD strains and determine their epidemiological significance by multilocus sequence typing (MLST). Methods In the 6-year period over 600 samples of grapevine, other wild/reservoir plants, Scaphoideus titanus and other potential vectors from different regions of Croatia were collected countrywide and analysed. Triplex real-time PCR was performed for detection together with PCR/RFLP of 16S rDNA. Detected FD phytoplasma isolates were characterised by MLST of secY, map and uvrB-degV genes. Conclusions FD-related phytoplasmas were found for the first time in alder, invasive tree species Ailanthus altissima and leafhopper Phlogotettix cyclops. Phylogenetic analyses of FD phytoplasma isolates revealed the existence of 3 mapFD strain clusters: mapFD1, mapFD2 and mapFD3, with the mapFD2 being prevalent. In addition, 7 uvrB-degV and at least 5 secY genotypes have been detected. Finding of all 3 mapFD clusters and different distribution of genotypes based on MLST suggests separate routes of the disease introduction and propagation origins in Croatia. Tentative role of P.cyclops in transmission of FD phytoplasma is also indicated.

epidemiology, genotyping, grapevine, phytoplasmoses

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