|HUANG, CHENG-HUA - University Of Florida|
|VALLAD, GARY - University Of Florida|
|ADKISON, HEATHER - University Of Florida|
|SUMMERS, CARLY - University Of Florida|
|MARGENTHALER, ELAINA - University Of Florida|
|SCHNEIDER, CHRISTINA - University Of Florida|
|JONES, JEFFREY - University Of Florida|
|ONG, KEVIN - Texas A&M University|
|NORMAN, DAVID - University Of Florida|
Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2013
Publication Date: 10/1/2013
Citation: Huang, C., Vallad, G.E., Adkison, H., Summers, C., Margenthaler, E., Schneider, C., Jones, J.B., Hong, J.C., Ong, K., Norman, D.J. 2013. A novel Xanthomonas sp. causes bacterial spot of rose (Rosa spp.). Plant Disease. 97(10):1301-1307. https://doi.org/10.1094/PDIS-09-12-0851-RE.
Interpretive Summary: In 2007 and 2008 samples from shrub rose bushes were collected from an outdoor nursery. These leaves exhibited small black lesions, well defined margins, and chlorosis was associated with the lesions. When plated the colonies were characteristic of Xanthomonas spp. The same symptoms or rose were reported previously in Florida and in Texas, yet it was not published. Sequencing and comparison of the 16s of these strains to known xanthomonads indicated that these strains were closely associated with X. axonopodis. Multilocus sequence typing confirmed this association. Pathogenicity test confirmed that this strain causes bacterial spot of rose and it is pathogenic on another Rosaceae, Indian Hawthorne (Rhaphiolepis indica).
Technical Abstract: A severe bacterial spot of rose (Rosa spp.) caused by a xanthomonad was observed in Florida and Texas. A total of 11 strains were collected from the two states. Multilocus sequence typing and analysis (MLST/MLSA) and pathogenicity tests were conducted to characterize the Xanthomonas strains. The MLSA based on six gene portions—fusA, gapA, gltA, gyrB, lacF, and lepA—showed that the rose strains of Xanthomonas fell into X. axonopodis subgroup 9.2. However, principal coordinate analysis grouped the rose strains into a unique cluster distinct from other members of the subgroup according to virulence phenotypes on 11 plant species belonging to five plant families (Araceae, Euphorbiaceae, Rosaceae, Rutaceae, and Solanceae). The rose strains were highly aggressive on Rosaceae probably resulting from host adaption that is common to Xanthomonas. On the basis of the MLSA and virulence phenotypes, it is proposed that the rose strains be classified as a pathovar of X. axonopodis and named X. axonopodis pv. rosa according to nomenclatural decisions described previously. Although without further study the date of specialization for X. axonopodis pv. rosa was not known, our sequence data analysis suggested that the pathovar was likely clonal, showed few mutations, and had developed under a purifying selective pressure that resulted in the predominance of a few haplotypes.