Phytoplasma, proteobacterium and fungus in single and mixed infections of sugar beet in central Europe

Abstract

The “basses richesses” syndrome (SBR) and rubbery taproot disease (RTD) associated with ‘Candidatus Arsenophonus phytopathogenicus’ and ‘Ca. Phytoplasma solani’, respectively are hampering the sugar beet production in Europe. A series of experiments shed light on the presence of these bacteria in sugar beet in central Europe - Pannonian plain (Serbia and Slovakia), with epidemic occurrences of RTD, and Germany. Only ‘Ca. P. solani’ was found in sugar beet in the Pannonian plain, while both pathogens were present in Germany. Reptalus quinquecostatus was identified as the insect vector responsible for the of the epidemic strain of ‘Ca. P. solani’ and thus for the epidemic occurrence of RTD. The RTD affected sugar beet is susceptible to charcoal root rot caused by Macrophomina phaseolina which exacerbates the losses associated to the phytoplasma presence. These results suggest that more attention should be given to phytoplasma infection in sugar beet in Europe.