Detection and identification of phytoplasmas associated with declining Liquidambar styraciflua trees in Colombia

Abstract

Liquidambar styraciflua was introduced in Bogota (D. C.) Colombia, in the 1990s as an urban tree. Yellowing and deformation of the tree crowns began to appear in 2007, leading to the hypothesis of a possible phytoplasma infection. To detect and identify phytoplasmas, samples were collected from 21 liquidambar trees from Bogota in 2009, 2010 and 2011 and subjected to nested PCR, RFLP and sequencing analyses of 16S ribosomal DNA. Nested PCR assays with group-specific primers and RFLP analyses identified phytoplasmas belonging to the 16SrI-B (aster yellows), 16SrV-B (jujube witches’ broom), 16SrVII-A (ash yellows), 16SrIX (pigeon pea witches’ broom) and 16SrXII-A (“stolbur”) groups/subgroups, in single or mixed infections. Sequence analysis and phylogenetic evaluation of samples with single phytoplasma infections confirmed the presence of phytoplasmas related to ‘Candidatus Phytoplasma asteris’, ‘Ca. P. fraxini’, and ‘Ca. P. solani’. In 2010 and 2013 two further surveys involving 100 trees each time were carried out to estimate the prevalence of the disease: the average prevalence with severe symptoms was 28%, with mild symptoms, 56%, and with minor symptoms 16% of the trees. No symptomless trees were observed. Phytoplasma presence in liquidambar trees from Bogota carries economic, environmental and epidemiological consequences, and urgent measures should be implemented to avoid the spreading of the disease to other tree species and to the agricultural areas surrounding the city.