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Title: Deep characterization of the microbiomes of Calophya spp. (Hemiptera: Calophyidae) gall-inducing psyllids reveals the absence of plant pathogenic bacteria and three dominant endosymbionts

item OVERHOLT, WILL - Georgia Institute Of Technology
item DIAZ, RODRIGO - University Of Florida
item Rosskopf, Erin
item GREEN, STEFAN - University Of Illinois
item OVERHOLT, WILLIAM - University Of Florida

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2015
Publication Date: 7/7/2015
Citation: Overholt, W., Diaz, R., Rosskopf, E.N., Green, S., Overholt, W. 2015. Deep characterization of the microbiomes of Calophya spp. (Hemiptera: Calophyidae) gall-inducing psyllids reveals the absence of plant pathogenic bacteria and three dominant endosymbionts. PLoS One. 10(7):e0132248. doi: 10.1371/journal.pone.0132248.

Interpretive Summary: A gall-inducing psyllid belonging to the genus Calophya has been tested in a quarantine facility for its potential as a biological control agent for the important invasive species, Schinus terebinthifolia, known as Brazilian peppertree. This noxious weed, now estimated to cover more than 280,000 ha of land in the state of Florida, causes significant reductions in native plant community diversity. The gall-inducing psyllid causes chlorosis, deformation, and abscission of Brazilian peppertree leaves. The Calophya spp. currently being tested have narrow host ranges, but other psyllid species are known vectors of serious plant pathogenic bacteria. These bacteria include the serious citrus pathogen belonging to species of 'Candidatus Liberibacter'. Although Calophya have not been associated with plant pathogenic bacteria, testing for these organisms is prudent prior to its release as a biological control agent. Previous studies were conducted, using species-specific primers, to test for important pathogens and it was determined that C. latiforceps does not harbor ‘Ca. L. solanacearum, ‘Ca. L. asiaticus’, ‘Ca. L. americanus’, or ‘Ca. L. africanus’. In the current study, additional work was done to determine if any other species of Liberibacter or related Phytoplasmas could be detected through ultra-high-throughput sequencing of bacterial rRNA extracted from Calophya populations in containment. The Calophya microbiomes had a relatively simple community, with 49-79 detected operational taxonomic units (OTUs). All of the OTUs were screened to determine if any were Liberibacters or Phytoplasmas and none were detected, providing further support that the release of these psyllids for control of Brazilian peppertree presents little to no risk of carrying plant pathogenic bacteria of other plant species.

Technical Abstract: Bacteria associated with sap-feeding insect herbivores include not only symbionts that may increase their hosts’ fitness, but also harmful plant pathogens. Calophya spp., gall-inducing psyllids (Hemiptera: Calophyidae), are being investigated for their potential as biological control agents of the noxious weed, Brazilian peppertree (Schinus terebinthifolia), in Florida. Although there are no examples of plant pathogen transmission by members of the family Calophyidae, several insects in the superfamily Psylloidea are known to transmit pathogenic Liberibacters and Phytoplasmas. To determine whether Calophya spp. harbor potentially harmful plant pathogenic bacteria, the 16S ribosomal RNA gene of individuals from four Calophya spp. populations were sequenced. All rRNA sequences fell into the bacterial domain, with 98-99% belonging to the Proteobacteria. The Calophya microbiomes were a relatively simple community, with 49-79 Operational Taxonomic Units (OTUs), and 5-8 OTUs with greater than 1% abundance. Candidatus Carsonella was the most abundant group, with OTUs representing between 51 – 65% of the total community. The next most abundant clade was affiliated with an unclassified Enterobacteriacae group similar to Buchnera that ranged from 20-31% in abundance. Wolbachia populations were the third most abundant group and represented 7-27% of the diversity in microbial OTUs. No Liberibacters or Phytoplasmas were detected in the microbiomes of the four Calophya populations. Based on these results, release of Calophya spp. from these populations in the United States poses no risk of introducing plant pathogenic bacteria into Florida.