Identification of Trichderma harzianum in postharvest Agaricus bisporus and a novel control approach using eucalyptus essential oil emulsion

Pathogenic infections have been a key factor leading to mushroom deterioration. However, few studies have focused on the isolation, identification, and control of pathogens causing infections in mushroom. In this study, the Trichoderma harzianum strain TPS2 was screened from the tissues of infected Agaricus bisporus. To inhibit the pathogenic microorganism, the eucalyptus essential oil (EEO)-tamarind gum (TG) emulsion was prepared and its antimicrobial mechanism and preservative effect of postharvest Agaricus bisporus were explored through emulsion fumigation. According to the in vitro experiment results, the EEO-TG emulsion induced the accumulation of reactive oxygen species, lipid peroxidation of the cell membrane, and destruction of cell membrane integrity. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results further revealed that the EEO-TG emulsion damaged the membrane permeability of T. harzianum, thereby resulting in the increased leakage of mycelial cell contents and achieving the antimicrobial effect. As the essential oil concentration in the EEO-TG emulsion increased, the effect on T. harzianum intensified. The ratio of EEO to TG at 1:10 was the minimum inhibitory concentration (MIC100), and the median inhibitory concentration (MIC50) was 1:40. In situ experiments, mushrooms fumigated with the EEO-TG emulsion exhibited high firmness, high whiteness, low electrical conductivity, and low weight loss, along with effective inhibition of the respiratory intensity and reduction in the excessive loss of nutrients. Therefore, the EEO-TG emulsion is of great significance in preventing postharvest diseases symptoms and delaying the senescence of mushrooms.