Epsilon-poly-l-lysine and methyl jasmonate synergistically inhibit Pseudomonas tolaasii-caused brown spot disease in postharvest button mushroom (Agaricus bisporus)

Abstract

The brown spot disease, caused by Pseudomonas tolaasii is a serious disease that significantly affects the quality of Agaricus bisporus. To develop a safe and effective method to protect mushrooms from disease, the effects of epsilon-poly-l-lysine (ε-PL) and methyl jasmonate (MeJA), either alone or in combination, on brown spot disease caused by P. tolaasii in A. bisporus were investigated. Our results showed that both ε-PL (100 mg L−1) and MeJA (100 μmol L−1) effectively reduced the incidence rate and disease index, inhibited the activity of polyphenol oxidase activated by P. tolaasii, and suppressed the production of malonaldehyde, and their combination achieved a more effective effect; the reason for this result was not due to their coordinated antibacterial activity in vitro, but rather the synergistic induction of disease resistance in mushrooms. The combined treatment of ε-PL and MeJA not only increased the content of pathogenesis-related proteins (PRs), the activities of defense enzymes and antioxidant enzymes, but also enhanced the activities of phenylpropanoid pathway-related enzymes and the accumulation of total phenolic and total flavonoid substances. Furthermore, the combined treatment was also more effective in increasing JA levels and the activities of lipoxygenase and allene oxide synthase compared to treatment with either ε-PL or MeJA alone. Correlation analysis further demonstrated the important role of defense-related enzymes and PRs as well as phenylpropanoid pathway-related enzymes and metabolites in the inhibition of ε-PL and MeJA alone or in combination on the incidence rate and disease index. Taken together, our results showed that ε-PL combined with MeJA treatment has good prospects for alleviating mushroom brown spot disease.