Archivio Journal of Plant Pathology

Abstract:

Carrot psyllid (Trioza apicalis Förster) causes considerable damage to carrot (Daucus carota L.) in many parts of Europe. It was recently established that the new bacterium “Candidatus Liberibacter solanacearum” is associated with carrot psyllid and plants affected by this insect. No other pathogens have so far been associated with T. apicalis-affected carrots, despite symptoms resembling those caused by phytoplasmas and spiroplasmas. Potential association of these pathogens with symptomatic carrots was investigated. Carrot samples and psyllids were collected in southern Finland and tested for phytoplasmas, spiroplasmas, and liberibacter by PCR. Liberibacter was detected in 5.5, 31.3, and 80% of asymptomatic samples, plants with leaf curling only, and plants with both leaf curling and discoloration, respectively. Liberibacter was also detected in 70% of the carrot psyllid samples. Only aster yellows phytoplasma (16SrI-A) was detected in 20% of carrot samples showing both leaf curling and discoloration. No phytoplasma was detected in the carrot psyllid samples. Mixed infection of both phytoplasma and liberibacter was detected in 20% of symptomatic plants. No spiroplasma was detected in plants or insects. To our knowledge, this is the first report of aster yellows phytoplasma in carrot in Finland and mixed infection of liberibacter and phytoplasma in carrot.