Evaluation of Virulence Factors of Pseudomonas tolaasii Paine 1919 Causing Brown Blotch on Edible Mushroom Agaricus bisporus (J.E. Lange) Imbach (1946)

Abstract

The study was carried out in the Laboratories of the College of Agriculture, University of Tikrit. 12
bacterial isolates taken from the casing layers in different mushroom farms in Iraq (Al-Wadaqq
Company, Erbil Company and Tikrit University Farm) were tested. The pathogenicity of the bacterial
isolates was tested on healthy fruit bodies of the edible mushroom Agaricus bisporus (J.E. Lange)
Imbach (1946) A15. The results showed the superiority of Mq7 bacteria isolate over the other isolates, with the highest infection rate of 69.6%. This isolate was molecularly identified to the level of Pseudomonas tolaasii Paine 1919 using nucleotide sequencing technology for the ITS1-ITS4 region of the 16 S rRNA gene. Then it was registered in the World Genetic Bank under the accession number MW737416.1, in a study evaluating the efficacy of some virulence factors of these bacteria, which included β-Glucanase, Chitinase and Protease enzymes. Purification of enzymes was carried out using ammonium sulfate precipitation, gel filtration chromatography (Sephadex G-150), and ion exchange chromatography (DEAE-cellulose). The effectiveness of 5 microelements including Fe, Mn, Mo, Zn and Bo was tested in inhibiting the activity of purified enzymes from pathogenic bacteria P. tolaasii Paine 1919. The results showed that for Zn, Mn and Fe at a concentration of 400 ppm was recorded the highest inhibition of β-Glucanas, as the specific activity reached 1.77, 2.73 and 2.98 units/mg protein, respectively, compared to 15.89 units/mg protein in control. Mo, Fe Iron and Zn in concentration of 400 ppm, showed the highest inhibition of Chitinase with a correspondent specific activities of: 3, 3.1, and 3.45 units/mg protein, respectively, compared to 42.64 units/mg protein in control. Zn and Fe in the same concentration recorded the highest inhibition of Protease, with corespondent specific activities of 5.65 and 7.79 units/mg protein, respectively, compared with 50.93 units/mg protein in control.