|Munyaneza, Joseph - Joe|
Submitted to: European Journal of Plant Pathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/17/2011
Publication Date: 12/20/2011
Citation: Munyaneza, J.E., Lemmetty, A., Nissinen, A.I., Sengoda, V.G., Fisher, T.W. 2011. Molecular detection of aster yellows phytoplasma and 'Candidatus Liberibacter solanacearum' in carrots affected by the psyllid Trioza apicalis (Hemiptera: triozidae) in Finland. European Journal of Plant Pathology. 93(3):697-700. Interpretive Summary: The carrot psyllid is a serious pest of carrots in northern and central Europe, where it can cause up to 100% crop loss. Mechanisms by which this insect causes damage to carrots are not yet known. Researchers at the USDA-ARS Wapato, in collaboration with scientists at MTT Agrifood Research in Finland, identified plant pathogens associated with carrots affected by this insect pest. It was determined that carrots exhibiting psyllid damage symptoms were infected with aster yellows phytoplasma and Liberibacter, a new species of bacterium recently found to severely affect potatoes and several other crops in North and Central America and New Zealand. Information from this research will help affected carrot producers in Europe and elsewhere reduce damage caused by these plant pathogens by effectively monitoring and managing the carrot psyllid.
Technical 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 pest. No other pathogens have so far been associated with affected carrots, despite the fact that the plant symptoms resemble those caused by leafhopper-transmitted phytoplasmas and spiroplasmas. Potential association of these pathogens with carrots exhibiting psyllid damage symptoms was investigated. Carrot samples and psyllids were collected from commercial fields in Finland and tested for phytoplasmas, spiroplasmas, and liberibacter by PCR. DNA samples extracted from carrot plants and psyllids were amplified by nested PCR using primer pairs P1/16S-Sr and R16F2n/R2 or P1/P7 and fU5/rU3 for phytoplasma detection and ScR16F1/ScR16R1 and ScR16F1A/ScR16R2 for spiroplasmas. PCR primers OA2/OI2c were used to amplify “Ca. L. solanacearum”. 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 carrot psyllid samples. Only aster yellows phytoplasma (16SrI-A) was detected in 10 and 20% of carrot samples showing both leaf curling and discoloration, when tested with primer pairs P1/16S-Sr and R16F2n/R2, and P1/P7 and fU5/rU3, respectively. No phytoplasma was detected in the psyllid samples. Mixed infection of both phytoplasma and liberibacter was detected in 20% of plants exhibiting both leaf curling and discoloration. No spiroplasma was detected in the plant or insect samples. This is the first report of aster yellows phytoplasma in carrot in Finland and mixed infection of liberibacter and phytoplasma in carrot.