Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: March 25, 2005
Publication Date: June 1, 2005
Citation: Lee, I., Bottner, K.D., Munyaneza, J.E., Davis, R.E., Crosslin, J., Du Toit, L., Crosby, T. 2005. Carrot purple leaf: a new carrot disease associated with Spiroplasma citri and phytoplasmas in Washington. Phytopathology. 95:S57.
During 2003/2004 a new disease outbreak occurred in several carrot fields located in south central Washington. In the fall, the affected carrot plants exhibited extensive purple or yellowish purple leaf discoloration; general stunting of shoots and tap roots; and formation of bunchy, fibrous secondary roots. PCR assays using primers specific to phytoplasmas and to plant pathogenic spiroplasmas were employed for the detection of putative causal agents. RFLP analyses of PCR-amplified 16S rDNA sequences revealed that all the symptomatic plants showing characteristic purple leaf symptoms (about 81%) tested positive for Spiroplasma citri. Plants showing mild purple discoloration symptoms tested positive for a phytoplasma strain (about 13%) belonging to the clover proliferation group (16SrVI), subgroup 16SrVI-A, and for another phytoplasma strain (about 1%) belonging to the aster yellows group (16SrI), subgroup 16SrI-A. Nucleotide sequence analysis of cloned 16S rDNA confirmed the identification based on RFLP analysis. Several symptomatic plants were doubly infected by both S. citri and one of the two phytoplasma strains.