Dear Jan Nechwatal

During my research on disease samples, I rarely noticed bacterial symptoms.

Vein-delimited angular lesions resulting from foliar nematode infection of Salvia sp. , Alternaria leaf spot, corynespora leaf spot, and powdery mildew , Peronospora antirrhini, Peronospora sp. Also noticed viral symptoms.

Pls. find the attached files

http://extension.psu.edu/pests/plant-diseases/all-fact-sheets/ralstonia

http://ipm.illinois.edu/diseases/series600/rpd607/

http://homeguides.sfgate.com/leaf-spots-salvia-madrensis-33885.html

http://link.springer.com/article/10.1007/s13213-013-0614-0

http://www.hdc.org.uk/sites/default/files/research_papers/HNS%20178%20year%201%20report.pdf

page 221. In: Akos Máthé. 2015. Medicinal and Aromatic Plants of the World: Scientific, Production, Commercial and Utilization Aspects. Springer,Pp.460. ISBN9401798109, 9789401798105

http://www.ct.gov/caes/lib/caes/documents/publications/fact_sheets/plant_pathology_and_ecology/identification_and_management_of_diseases_of_perennials_in_the_landscape_04-02-08r.pdf

http://www.ncbi.nlm.nih.gov/pubmed/24175532

Hoping this will be helpful            

Regards

Prof. Houda Kawas

Jan, 

it is mentioned in several seed testing manuals, that Salvia seeds can be infected by different bacteria, and Steve Roberts has described Pseudomonas syringae Gr1b as Salvia pathogen (http://www.hdc.org.uk/sites/default/files/research_papers/HNS%20178%20year%201%20report.pdf), but so far nobody has identified any certain xanthomonads associated with this plant. I guess it can be related to X. hortorum or X. arboricola. 

Regards

Alex

First of all, could you reproduce the symptoms with your isolate on Salvia? If not, you may waist your time for a non-disease inducer strain.

Sandor

Sandor, you're right. Indeed, we have problems with reproducing these symptoms. However, as it is in general difficult to reproduce symptoms for many bacterial leaf spot diseases - you never can be sure. It might as well be a problem of different environmental conditions (or similar) in your test setup.

Sandor is right, some leaf spot pathogens need highly specific condition for plant infection (hot or cold humid weather) , or they can be secondary pathogens that follow primary infection. 

As mentioned in the question, It was identified as X. sp. via biochemical tests and 16S DNA sequencing, even if its symptoms differ in different weather condition isn't it for the first time X. sp. on Salvia

Jan, because your PCR using gyrB primers failed I am afraid you do not have Xanthomonas isolates, although you may try  step by step:

-hypersensitivity on tomato (tobacco)

- infiltration of Salvia leaves, keeping them in humid condition for 48h

-  PCR using primers X1 and X2 specific for the genus Xanthomonas (Maes, 1993).

Thank you Sandor. But then, what about the16S sequences? I have just re-checked the sequences. Indeed, there are other genera in the Blast results if I scroll way down which share (almost) the same identity, score and e-value. So might be one of those? 

Sure, DNA sequencing studies of the 16S rRNA gene of Xanthomonas species have indicated that using 16S rRNA gene comparison could not differenciate the majority of Xanthomonas species from the members of the Gammaproteobacteria genus. That was reason that Parkinson et al. suggested the use of gyrB gene.

@ Jan Nechwatal

Please have a look at this useful RG link.

Conference Paper Bacterial leaf spot of Salvia nemorosa caused by Xanthomonas sp.

Thanks!