Multilocus genotyping identifies a highly homogeneous phytoplasma lineage associated with sweet cherry virescence disease in China and its carriage by an erythroneurine leafhopper

Authors: WANG, JIAWEI - Shangdong Institute Of Pomology; LIU, QINGZHONG - Shangdong Institute Of Pomology; Wei, Wei; Davis, Robert; TAN, YUE - Shangdong Institute Of Pomology; Lee, Ing Ming; ZHU, DONGZI - Shangdong Institute Of Pomology; WEI, HAIRONG - Shangdong Institute Of Pomology; Zhao, Yan

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2017
Publication Date: 4/1/2018
Citation: Wang, J., Liu, Q., Wei, W., Davis, R.E., Tan, Y., Lee, I., Zhu, D., Wei, H., Zhao, Y. 2018. Multilocus genotyping identifies a highly homogeneous phytoplasma lineage associated with sweet cherry virescence disease in China and its carriage by an erythroneurine leafhopper. Crop Protection. 106:13-22.

Interpretive Summary: Over a three-year period from 2013 to 2015, a disease repeatedly occurred in sweet cherry trees growing in Northern China. The disease was characterized by developing malformed flowers with green pigmentation that failed to set fruit. By using DNA fingerprinting technology, ARS scientists and Chinese collaborators determined that the cherry disease was associated with infection by phytoplasma, a bacterial pathogen that resides in plant nutrient-conducting vessels and is spread by sap-sucking insects. Results from further genotypic analysis of the cherry phytoplasma revealed that the pathogen is almost indistinguishable from those causing witches’-broom diseases of jujube and many other economically important crops in China. Although capable of infecting a wide range of host plants, these phytoplasmas formed a highly homogenous lineage. The study also brought to light a leafhopper that carries the phytoplasma and may play a role in spreading the disease. This report will be of interest to research scientists, diagnostics laboratories, and extension personnel who are concerned with genetic diversity of phytoplasmas and phytoplasmal disease management. This information is also important to regulatory agencies for implementing quarantine measures to prevent spread of the new pathogen.

Technical Abstract: Phytoplasmas are a diverse group of insect-transmitted, cell wall-less bacteria that colonize plant phloem sieve elements and cause numerous diseases in economically important crops. Living a trans-kingdom parasitic life, phytoplasmas possess dynamic genomes and evolve rapidly toward formation of distinct ecological lineages in their adaptation to specific ecological niches. In an effort aimed at identification of the etiological agent responsible for a repeatedly-occurring sweet cherry virescence (SCV) disease in China, we found that the SCV disease was consistently associated with infection by a phytoplasma belonging to subgroup B of the elm yellows phytoplasma group (16SrV-B). Further analysis of genetic loci that encode important phytoplasma cellular components, including an array of ribosomal proteins and preprotein translocase subunit SecY, revealed that the SCV phytoplasma was essentially indistinguishable from the phytoplasmas responsible for jujube witches’-broom (JWB) disease and diseases of many other plants. Evidence gathered in the present study indicated that SCV-JWB phytoplasma strains formed a highly homogenous ecological lineage. The study also revealed that a polyphagous leafhopper, Táoyidianyèchán (often being cited as Erythroneura sudra), was able to carry the SCV phytoplasma, emphasizing a need to investigate whether this erythroneurine leafhopper plays a role in spreading the SCV phytoplasma among sweet cherry plants.