Exploring the Pathogenocity of Pseudomonas brassicearum Q8r1-96 and Other Strains of the Pseudomonas fluorescens Complex On Tomato
Biological, Environmental, and Earth Sciences
Pseudomonas brassicacearum and related species of the P. fluorescens complex have long been studied as biocontrol and growth-promoting rhizobacteria involved in suppression of soilborne pathogens. We report here that P. brassicacearum Q8r1-96 and other 2,4-diacetylphloroglucinol (DAPG)-producing fluorescent pseudomonads involved in take-all decline of wheat in the Pacific Northwest of the United States can also be pathogenic to other plant hosts. Strain Q8r1-96 caused necrosis when injected into tomato stems and immature tomato fruits, either attached or removed from the plant, but lesion development was dose dependent, with a minimum of 106 CFU ml−1 required to cause visible tissue damage. We explored the relative contribution of several known plant-microbe interaction traits to the pathogenicity of strain Q8r1-96. Type III secretion system (T3SS) mutants of Q8r1-96, injected at a concentration of 108 CFU ml−1, were significantly less virulent, but not consistently, as compared with the wild-type strain. However, a DAPG-deficient phlD mutant of Q8r1-96 was significantly and consistently less virulent as compared with the wild type. Strain Q8r1-96acc, engineered to over express ACC deaminase, caused a similar amount of necrosis as the wild type. Cell-free culture filtrates of strain Q8r1-96 and pure DAPG also cause necrosis in tomato fruits. Our results suggest that DAPG plays a significant role in the ability of Q8r1-96 to cause necrosis of tomato tissue, but other factors also contribute to the pathogenic properties of this organism.
Mavrodi, D. V.,
Thomashow, L. S.,
Weller, D. M.
(2020). Exploring the Pathogenocity of Pseudomonas brassicearum Q8r1-96 and Other Strains of the Pseudomonas fluorescens Complex On Tomato. Plant Disease, 104(4).
Available at: https://aquila.usm.edu/fac_pubs/17393