Location: Molecular Plant Pathology
Title: Characterization and molecular differentiation of 16SrI-E and 16SrIX-E phytoplasmas associated with blueberry stunt disease in New Jersey Authors
Submitted to: Molecular and Cellular Probes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 19, 2012
Publication Date: April 1, 2013
Citation: Bagadia, P.G., Polashock, J.J., Bottner-Parker, K.D., Zhao, Y., Davis, R.E., Lee, I. 2013. Characterization and molecular differentiation of 16SrI-E and 16SrIX-E phytoplasmas associated with blueberry stunt disease in New Jersey. Molecular and Cellular Probes. 27:90-97. Interpretive Summary: Blueberries are susceptible to blueberry stunt disease, caused by a bacteria-like organism called a phytoplasma. Recently the recurrence of blueberry stunt disease occurred in New Jersey. The phytoplasmas causing the disease in New Jersey have never been characterized, prompting us to conduct a large scale field survey. We conducted a state-wide survey of the causal pathogens of blueberry stunt disease present in all blueberry cultivars in several major blueberry production counties throughout New Jersey. Using molecular techniques for identification, we identified two different phytoplasmas, one of them new. There was no significant difference in the rate of disease incidence among various blueberry cultivars. This is the first report that more than one phytoplasma is the cause of blueberry stunt disease in the US. The information will be interesting for peer scientists, graduate students, extension workers and plant diagnosticians and will aid implementation of quarantine regulation and help to determine how to combat the disease.
Technical Abstract: A nested PCR assay was employed to detect the presence of phytoplasmas associated with 127 symptomatic blueberry plants collected during the 2010 and 2011 growing seasons from 11 commercial farms predominantly located in two major blueberry-growing counties in New Jersey, USA. Ninety plants exhibiting typical stunt syndrome tested positive for phytoplasma infection. Restriction fragment length polymorphism analysis indicated that two distinct phytoplasmas were associated with the diseased plants. About 95% of phytoplasmas detected were very closely related to blueberry stunt strains BBS3-AR (16SrI-E) and BBS1-MI (16SrI-E variant) identified previously. Phytoplasmas associated with four diseased plants from three farms belong to the pigeon pea witches’-broom phytoplasma group (16SrIX). Sequence and phylogenetic analysis of cloned 16S rDNA further indicated the 16SrI-E related phytoplasmas detected in diseased blueberry plants represented a 16SrI-E variant while the 16SrIX related phytoplasmas were closely related to juniper witches'- broom (JunWB) phytoplasma (16SrIX-E), representing a 16SrX-E variant. Ribosomal protein (rp) and secY gene-based phylogenies revealed that BBS-AR and NJ 16SrI-E strains belonged to a closely related lineage, while NJ 16SrIX-E strains and JunWB strains represented two distinct lineages. Single nucleotide polymorphisms (SNP) analyses based on rp and secY gene sequences further revealed that NJ BBS 16SrI-E related strains had identical rp SNPs and very similar secY SNPs profiles to those of BBS3-AR. The BBS 16SrIX-E related strains/clones, however, had 28 consensus SNPs that separated them from JunWB strains. Several distinct rp and secY SNP pattern types were identified among these strains, implying the presence of heterogeneous strain populations.