Multilocus Genotyping of ' Phytoplasma solani' Associated with Rubbery Taproot Disease of Sugar Beet in the Pannonian Plain.

Rubbery taproot disease of sugar beet (RTD), associated with ' Phytoplasma solani', appeared in 2020 on an epidemic scale in northern Serbia and southern Slovakia, situated at opposite edges of the Pannonian Plain. In the affected locations where the disease was assessed, symptomatic sugar beets were analysed for phytoplasma infection. Additionally, multilocus sequence analyses of '. P. solani' strains on epidemiologically informative marker genes (, and ) were performed. Symptomatic sugar beets from other countries of the Pannonian Plain (Croatia, Hungary and Austria), one sample from Germany, and red beets from Serbia were included in the analyses. '. P. solani' was detected in sugar beet in all assessed countries, as well as in red beet. Molecular analyses revealed the high genetic variability of '. P. solani' with the presence of all four types (a, b1, b2 and d), 14 genotypes (seven new) and five profiles (one new). The most common multilocus genotype in Serbia, Slovakia, Croatia, and Hungary was dSTOLg (tuf-d/STOL/V2-TA). It was dominant on sites with epidemic RTD outbreaks in the Pannonian Plain and in several sugar beet fields with non-epidemic RTD occurrence suggesting the prevalence of a particular epidemiological pathway during the epidemic's phases.