Allelopathic effects of phenolic acid extracts on Morchella mushrooms, pathogenic fungus, and soil-dominant fungus uncover the mechanism of morel continuous cropping obstacle.

The prominent problem of continuous cropping obstacle has been frustrating the morel farming. To deepen the understanding on morel continuous cropping obstacle, the allelopathic effects of phenolic acid extracts from morel continuous cropping soils on growth and development of Morchella sextelata, M. eximia, M. importuna, pathogenic fungus Fusarium sp. and soil-dominant fungus Chaetomium sp. were investigated. These effects were expressed as response index (RI). Under actual content of phenolic acids (6.150 μg/g fresh mixed continuous cropping soil), the mycelial growth of all tested morel strains was inhibited (RI < 0), while the allelopathic effect of control phenolic acids (4.252 μg/g fresh mixed control soil) was between promotion and inhibition, which suggested that the phenolic acid extracts from morel continuous cropping soils may exhibit certain extent of autotoxicity for the existence of morel-specific allelochemicals. In addition, the aggravated pigmentation and reduced occurrence of sclerotium in three Morchella fungi at growth inhibitory concentrations of phenolic acids indicated the induction of morel strain aging. Meanwhile, most concentrations of phenolic acids showed stimulatory effects on sporulation of Fusarium sp. and Chaetomium sp. (RI > 0), manifesting the enrichment of soil-borne pathogenic fungi and dominance of certain fungal population in soil ecosystem. Collectively, the allelopathic effects of phenolic acid extracts play an instrumental role in morel continuous cropping obstacle. The study will be beneficial for healthy development of morel artificial cultivation.