Using bacteria for biocontrol: how Pseudomonas fluorescens defeats the common potato scab

By Steven Harris

Based on a seminar given by Dr Tanya Arseneault written in the style of a Letter to Nature summary paragraph.

Common scab is a potato disease caused by the bacterium Streptomyces scabies (1,2). Streptomyces scabies induces common scab disease by the production of extracellular esterases and the toxin thaxtomin A, which damages the surface of potatoes (Solanum tuberosum) (3,4). Common scab disease is ineffectively controlled currently, with hypotheses suggesting the potential for biocontrol measures to be implemented using Pseudomonas fluorescens (4). Yet the implementation of Pseudomonas fluorescens as a biocontrol has not occurred with the success rate of tuberous crop protection requiring further investigation. Here we show Pseudomonas fluorescens sp. LBUM223 produced the antibiotic phenazine-1-carboxylic acid (PCA) to kill Streptomyces scabies soil pathogens and reduce the virulence of Streptomyces scabies. We found that the production of PCA induced a reduction in thaxtomin A production in Streptomyces scabies, the toxin responsible for common scab disease in potatoes (5,6). Moreover Pseudomonas fluorescens LBUM223 was capable of promoting plant growth regardless of Streptomyces scabies presence. We conclude that decreases in the known virulence factor thaxtomin A enable a reduction in common scab symptoms, increasing potato yield5. Our results express the importance Pseudomonas fluorescens LBUM223 has in future biocontrol of common scab disease, illustrating the possible benefits to agriculture and the field of phytopathology Pseudomonas fluorescens LBUM223 possesses.

References

1. Han L, Dutilleul P, Prasher S, Beaulieu C, Smith D. Assessment of Common Scab-Inducing Pathogen Effects on Potato Underground Organs Via Computed Tomography Scanning. Phytopathology. 98(10), 1118-1125 (2008)

2. Takeuchi T, Sawada H, Tanaka F, Matsuda I. Phylogenetic Analysis of Streptomyces spp. Causing Potato Scab Based on 16S rRNA Sequences. International Journal of Systematic Bacteriology. 46(2), 476-479 (1996)

3.Kiss, Z., Dobránszki, J., Hudák, I., Birkó, Z., Vargha, G. and Biró, S. (2010). The possible role of factor C in common scab disease development. Acta Biologica Hungarica. 61(3), 322-332 (2010)

4. St-Onge R, Gadkar V, Arseneault T, Goyer C, Filion M. The ability of Pseudomonas sp. LBUM 223 to produce phenazine-1-carboxylic acid affects the growth of Streptomyces scabies, the expression of thaxtomin biosynthesis genes and the biological control potential against common scab of potato. FEMS Microbiology Ecology. 75(1), 173-183 (2010).

5. Arseneault T, Goyer C, Filion M. Pseudomonas fluorescens LBUM223 Increases Potato Yield and Reduces Common Scab Symptoms in the Field. Phytopathology. 105(10), 1311-1317 (2015)

6. Roquigny R, Arseneault T, Gadkar V, Novinscak A, Joly D, Filion M. Complete Genome Sequence of Biocontrol Strain Pseudomonas fluorescens LBUM223. Genome Announcements. 3(3), e00443-15 (2015)

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