Skip to main content
ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Molecular Plant Pathology Laboratory » Research » Publications at this Location » Publication #324730
Title: First Report of a New ‘Candidatus Phytoplasma pini’-related strain Associated with Witches’-broom of Virginia pine in Maryland

Author
item COSTANZO, S - Animal And Plant Health Inspection Service (APHIS)
item RASCOE, J - Animal And Plant Health Inspection Service (APHIS)
item NAKHLA, K - Animal And Plant Health Inspection Service (APHIS)
item Zhao, Yan
item Davis, Robert

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/22/2016
Publication Date: 6/7/2016
Citation: Costanzo, S., Rascoe, J., Nakhla, K., Zhao, Y., Davis, R.E. 2016. First Report of a New ‘Candidatus Phytoplasma pini’-related strain Associated with Witches’-broom of Virginia pine in Maryland. Plant Disease. 100:1776. doi.org/10.1094/PDIS-01-16-0097-PDN.

Interpretive Summary: Phytoplasmas are minute, specialized bacteria causing plant diseases that result in economic losses worldwide. They are spread by insects that feed in the food conducting tissues in veins, where phytoplasmas live and induce disease symptoms including development of abnormally small leaves. Phytoplasmas can be introduced into new geographic regions by the transportation and cultivation of vegetatively propagated, infected plant parts that serve as a source of phytoplasma for spread to crops in the new region. To reduce the spread of phytoplasmas, it is important to know whether or not a given plant is or can be infected by a phytoplasma. In this work, we discovered a previously unknown phytoplasma infecting a diseased pine tree that was exhibiting abnormal shoot branching and witches’ broom symptoms. We extracted and analyzed DNA from the diseased tree and found that the tree was infected by a phytoplasma that is related to (but distinct from) ‘Candidatus Phytoplasma pini’, the cause of a serious disease threatening pine trees in Europe. Our discovery expands knowledge of plant diseases that can be caused by phytoplasmas, and it provides molecular markers for assessing whether the MDPP phytoplasma poses a new threat to pine forests.

Technical Abstract: In April of 2015, a pine tree (Pinus virginiana Mill.) in Laurel, Maryland was observed to have abnormal shoot branching and witches’ broom symptoms. Total nucleic acids were extracted from needles collected from a symptomatic branch. Polymerase chain reaction assays (PCRs) for amplification of the 16S ribosomal (r) RNA gene (rDNA) sequences and secA genomic region were used to assess possible association of a phytoplasma with the disease. Nucleotide sequencing of amplicons confirmed that the tree was infected by a phytoplasma, designated as strain MDPP. The MDPP phytoplasma was classified as a member of group 16SrXXI using iPhyClassifier, an interactive online tool for phytoplasma classification and taxonomic assignment. The 16S rDNA sequence of strain MDPP shares 98.4% similarity with that of the ‘Candidatus Phytoplasma pini’ reference strain from Spain (isolate P127, GenBank accession: AJ632155). The phytoplasma under study was thus determined to be a ‘Candidatus Phytoplasma pini ’-related strain. The collective RFLP patterns of MDPP 16SrDNA were distinct from the reference patterns of all previously delineated subgroups; MDPP therefore appears to represent a new subgroup, designated 16SrXXI-B. To our knowledge, this is the first report of a ‘Ca. Phytoplasma pini’-related strain associated with pine in North America and possibly the entire western hemisphere.