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Title: Phytoplasma infecting cherry and lilac represent two distinct lineages having close evolutionary affinities with clover phyllody phytoplasma

item JOMANTIENE, RASA - Institute Of Botany - Lithuania
item Zhao, Yan
item Lee, Ing Ming
item Davis, Robert

Submitted to: European Journal of Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2010
Publication Date: 1/11/2011
Citation: Jomantiene, R., Zhao, Y., Lee, I., Davis, R.E. 2011. Phytoplasma infecting cherry and lilac represent two distinct lineages having close evolutionary affinities with clover phyllody phytoplasma. European Journal of Plant Pathology. 130:97-107.

Interpretive Summary: Phytoplasmas are very small bacteria that cause damaging diseases in agriculturally important crops and in plants growing in natural areas. There is need to determine whether phytoplasmas are involved in newly recognized diseases of plants, including diseases affecting fruit trees and woody ornamentals, and to identify phytoplasmas associated with emerging diseases, so that appropriate disease control measures may be devised based on knowledge of the disease-causing agents. The present work focused on diseases of cherry and lilac in Europe; the cause of the diseases was unknown. Using molecular methods for detection and identification, we found that phytoplasmas are the apparent cause of the diseases, which we have named cherry bunchy leaf (ChBL) and lilac little leaf (LcLL). The ChBL and LcLL phytoplasmas are related to a phytoplasma associated with disease of clover in North America and Europe, but both phytoplasmas represent previously undescribed lineages. Finding these phytoplasmas expands the known biodiversity of phytoplasmas discovered to infect woody plants. The data provide means for detecting and identifying the same phytoplasmas in cherry, lilac, and other plants around the world. Concepts presented in this report open new avenues for understanding the evolution of new phytoplasma lineages. This report will be of interest to diagnostics laboratories, research scientists, quarantine regulatory agencies, and growers.

Technical Abstract: Phytoplasmas infecting cherry and lilac in Lithuania were found to represent two lineages related to clover phyllody phytoplasma (CPh), a subgroup 16SrI-C strain exhibiting rRNA interoperon sequence heterogeneity. 16S rDNAs amplified from the cherry bunchy leaf (ChBL) and lilac little leaf (LcLL) phytoplasmas were identical or nearly identical to those of operon rrnA and operon rrnB, respectively, of CPh. There was no evidence of 16S rRNA interoperon sequence heterogeneity in either LcLL or ChBL phytoplasma. Based on collective RFLP patterns of 16S rDNA, ChBL was classified in subgroup 16SrI-R, and LcLL was classified in new subgroup 16SrI-S. The ribosomal protein (rp) gene sequences from LcLL phytoplasma were identical to those of CPh, and strain LcLL was classified in rp subgroup rpI-C. By contrast, rp gene sequences from ChBL phytoplasma differed from those of subgroup rpI-C; based on RFLP patterns of rp gene sequences, ChBL was tentatively classified in rp subgroup rpI-D. Single nucleotide polymorphisms (SNPs), designated here by a new SNP convention, marked members of rp subgroup 16SrI-C(rpI-C), and distinguished LcLL and CPh from ChBL and other non-16SrI-C(rpI-C) phytoplasmas. Further research is needed to understand the origins and evolutionary relationships of the three related lineages and to evaluate the possible role of horizontal gene transfer.