Incidence and characterization of the presence of phytoplasmas in Fraxinus uhdei related with Ash Yellow disease in Colombia

Abstract

For a long time, Urapan trees (Ash) have been a popular plant in parks and avenues in the principal cities of the Andes in Colombia, but now more than 53,000 trees are infected and many of them died. In 2004, the presence of phytoplasmas in the phloem of some trees with dieback symptoms was reported. In this study, the phytoplasma’s presence has been detected in all the tested Fraxinus uhdei (Wenz.) (common name, Urapan), using microscopy techniques like optical microscopy, transmission electron microscopy, and DAPI fluorescent microscopy, which indicated a further spread of the disease. The presence of phytoplasmas in the phloem of the leaves of Urapan trees was evident and related with the symptoms of the disease “Ash Yellows”. Here the relation phytoplasmas–disease symptoms have been confirmed by reproducing the symptoms through phytoplasmas transfection in Periwinkle (Catharanthus roseus) by using the ectoparasite Cuscuta campestris. The molecular analysis using PCR with universal primers of the region 16S-23S rDNA (P1/Timt, R16mF2/R16mR1, fB1/P7, fPD/Tint, F1/P7, Phytuf22/Phytuf24) confirmed the parasite’s presence and its identification as Ash Yellows phytoplasma or Candidatus Phytoplasma fraxini which belongs to the phytoplasma group 16SrVII and subgroup 16SrVII-A. These results permit to suggest a possible treatment with antibiotics that would avoid the species extinction throughout the Andes cities.