Manipulating button mushroom casing affects the disease dynamics of blotch and green mold disease

Productive cultivation of the button mushroom (Agaricus bisporus) relies on the use of selective substrates and effective disease management. In extending our previous work on manipulating the developmental microbiome (devome), this study employs the strategy of substrate passaging to explore its effects on crop outcomes and disease dynamics. Here we subjected the casing substrate to ten cycles of passaging. This manipulated substrate stimulated early pinning (primordia formation) by at least three days. Passaged casing also altered disease dynamics when challenged with two commercially important A. bisporus pathogens, Pseudomonas tolaasii (causing bacterial blotch) and Trichoderma aggressivum f. aggressivum (responsible for green mold). Passaged casing had a suppressive effect on blotch disease and a conducive effect on green mold disease. Blotch suppression resulted in a significantly higher yield of asymptomatic mushrooms in all three mushroom harvests (flushes) and in the overall crop yield. Blotch severity was also significantly reduced in passaged casing compared to standard casing due to a lower yield of mushrooms with the highest degree of blotch disease expression. Green mold disease expression was markedly higher in passaged casing, leading to lower numbers of asymptomatic mushrooms. Zones where no growth of hyphae or mushrooms were also observed in passaged casing due to green mold disease pressure. The stimulating effect of passaged casing on mushroom development and the dynamic outcomes for disease challenge from two distinct, commercially damaging diseases, demonstrates the potential for passaged casing to be used as material to study more sustainable mushroom production and disease management practices.