A new phytoplasma associated with little leaf disease in azalea: multilocus sequence characterization reveals a distinct lineage within the aster yellows phytoplasma group |
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| Authors: | Yi Jiang Ing‐Ming Lee Robert E Davis Yang Ding Enping Yuan Hairu Chen Yan Zhao |
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| Institution: | 1. Molecular Plant Pathology Laboratory, USDA‐Agricultural Research Service, Beltsville, MD, USA;2. The Key Laboratory for Plant Pathology, Yunnan Agricultural University, Kunming, China |
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| Abstract: | An azalea little leaf (AzLL) disease characterised by abnormally small leaves, yellowing and witches'‐broom growth symptoms was observed in suburban Kunming, southwest China. Transmission electron microscopic observations of single‐membrane‐bound, ovoid to spherical bodies in phloem sieve elements of diseased plants and detection of phytoplasma‐characteristic 16S rRNA gene sequence in DNA samples from diseased plants provided evidence linking the disease to infection by a phytoplasma. Results from restriction fragment length polymorphism, phylogenetic and comparative structural analyses of multiple genetic loci containing 16S rRNA, rpsS, rplV, rpsC and secY genes indicated that the AzLL phytoplasma represented a distinct, new 16Sr subgroup lineage, designated as 16SrI‐T, in the aster yellows phytoplasma group. The genotyping also revealed that the AzLL phytoplasma represented new rp and secY gene lineages rp(I)‐P and secY(I)‐O, respectively]. Phylogenetic analyses of secY and rp gene sequences allowed clearer distinctions between AzLL and closely related strains than did analysis of 16S rDNA. |
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| Keywords: | Azalea little leaf disease gene lineage multilocus sequence analysis phytoplasma Rhododendron spp |
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