Abstract
Volvariella volvacea is a typical edible Basidiomycete with a high-temperature tolerance. It has a strong fibrinolysis capability and consumes abundant agricultural wastes. In agricultural cultivation, mycelial subculturing has been adopted, leading to serious strain degeneration. In this study, continuous mycelial subculturing of the common V. volvacea strain V971 (original strain recorded as M0) was performed in potato dextrose agar (PDA) medium. One generation of the strain was preserved every 3 months (90 days); thus, six generations of degenerated strains (M1–M6) were obtained after 18 months of mycelial subculturing. The original and degenerated strains were preserved in sterile paraffin liquid at room temperature (18–25°C). The biological traits and nutrients of M0 and M1–M6 were studied. The mycelial growth rate and biomass initially increased and then decreased as the degeneration progressed, reaching minimum levels of 0.041 ± 0.001 cm/h and 1.82 ± 0.25 g, respectively, at M6. Additionally, the polysaccharide, protein, polyphenol, flavone, total amino acid, and total mineral element contents of the strains decreased continuously, reaching minimum levels of 30.12 ± 3.12 g/100 g, 26.42 ± 2.1 g/100 g, 1.08 ± 0.05 g/100 g, 4.23 ± 0.21 g/100 g, 12.51 mg/g, and 398.05 mg/kg, respectively, at M6. The decolorization capability of V. volvacea in liquid medium supplemented with bromothymol blue and lactose reflected the degree of strain degeneration, with the capability weakening as the degeneration intensified. These results are highly significant for V. volvacea production. The mycelial characteristics during subculture-associated degeneration were described and provide an early identification method for V. volvacea’s degeneration.
Highlights
Many edible mushroom species have been consumed as food and used as food flavoring for thousands of years
Subcultures of V. volvacea mycelia were passaged for 18 months, and the kinetic behaviors of the tested V. volvacea strains were assessed on potato dextrose agar (PDA) medium
Subcultures of V. volvacea mycelia were passaged for 18 months on PDA medium, and mycelial biomasses of M0–M6 were determined (Figure 2)
Summary
Many edible mushroom species have been consumed as food and used as food flavoring for thousands of years. They are an important drug source (Rai et al, 2005). Strain degeneration restricts the development of the edible mushroom industry and decreases their biotechnological values (Magae et al, 2005). The preservation of edible mushroom strains is difficult because they are often characterized by the inability to form resistant propagules in pure. Degenerated edible mushrooms are characterized by slim, fragile, and slow-growing mycelia (Magae et al, 2005; Kim et al, 2014)
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