Study on the effect of certain metabolites produced by Pseudomonas tolaasii and associated bacteria on Agaricus bisporus

In this research some metabolites of Pseudomonas tolaasii the causal agent of mushroom bacterial blotch disease and Pseudomonas reactans associated with it were investigated. Characteristic features of P. tolaasii included brown pit formation on button mushroom caps, tolaasin production, lysis of erythrocytes, and white line induction in agar plate in presence of Pseudomonas reactans. Further, the metabolites of P. tolaasii and mushroom-associated bacteria were extracted and their effects were evaluated against the blocks of the mushroom A. bisporus. It was noticed that the strains of P. reactans also produced a lipodepsipeptide, WLIP. Certain complementary tests were also conducted to confirm the presence of these compounds in products extracted. The rpoB gene of a pathogenic strain of Pseudomonas sp. p2 isolated from the same mushroom was amplified using the primer pair of LAPS and LAPS27 and sequenced and deposited in Genebank at NCBI. Effect of impure WLIP of the strain P. reactans Pr 5 and standard strain of P. reactans NCPPB1311 were examined on blocks of A. bisporus and potato tubers. In bioassays, the tolaasin of strain P. tolaasii Pt 6 created both brown blotch and slight pitting symptoms. Whereas, WLIP of the P. reactans Pr 5 could only induce slight discoloration. Another important finding was that simultaneous application of P. reactans A6 in combination with tolaasins of P. tolaasii Pt 6 or P. tolaasii NCPPB2192 resulted in suppression of brown blotch symptoms on treated blocks with P. tolaasii. Results indicate the importance of associated bacteria in suppression of disease by P. tolaasii.