Plant Pathology (2016) 65, 826-836

N. Jiang, Q.Y. Lv, X. Xu, Y.S. Cao, R.R. Walcott, J.Q. Li and L.X. Luo (2016)
Induction of the viable but nonculturable state in Clavibacter michiganensis subsp. michiganensis and in planta resuscitation of the cells on tomato seedlings
Plant Pathology 65 (5), 826-836
Abstract: Bacterial canker of tomato is an economically important seedborne disease caused by Clavibacter michiganensis subsp. michiganensis (Cmm). Copper-based bactericides and seed treatment with hydrochloric acid are commonly used for bacterial canker management. Recent studies have shown that some bacteria can enter a viable but nonculturable (VBNC) state, and fail to form colonies on microbiological agar media. Bacteria in the VBNC state can recover their culturability when returned to favourable conditions. This study reports the induction of the VBNC state in Cmm by CuSO₄ and low pH, and resuscitation of VBNC cells on tomato seedlings. Flow cytometry using the nucleic acid dyes SYTO 9 and propidium iodide, combined with agar plating, was used to assess VBNC cell counts. It was demonstrated that CuSO₄ and low pH induced the VBNC state in Cmm and the rate of induction increased with copper ion concentration and acidity. Pathogenicity tests showed that some of the VBNC cells induced by CuSO₄ retained their ability to colonize tomato seedlings but failed to produce typical bacterial canker symptoms by 2 months post-inoculation. This was probably due to low levels of resuscitation of VBNC Cmm cells resulting in low levels of initial inoculum. This study has improved understanding of the VBNC state of Gram-positive phytopathogenic bacteria. Most importantly, because copper-based chemicals and low pH conditions are used for disease management, induction of the VBNC state and subsequent resuscitation of Cmm cells on tomato seedlings may limit pathogen detection by culture-based assays yet present a risk for disease development in the field.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Laixin Luo, Ron Walcott

Research topic(s) for pests/diseases/weeds:
general biology - morphology - evolution

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Clavibacter michiganensis	Tomato (Solanum lycopersicum)