Autotoxicity of Endogenous Organic Acid Stress in Two Ganoderma Lucidum Cultivars

Summary

This research investigated why the medicinal mushroom Ganoderma lucidum cannot produce good quality mushrooms in second harvests from the same growing material. Scientists discovered that the mushroom releases organic acids during its growth that make its environment too acidic for healthy second growth. This self-poisoning effect helps explain why farmers must use new growing materials for each crop. Impacts on everyday life: • Helps mushroom farmers understand why they need fresh growing materials for each crop • Could lead to more efficient and sustainable mushroom cultivation methods • May reduce cultivation costs and waste in medicinal mushroom production • Provides insights that could improve the availability and affordability of this medicinal mushroom • Could contribute to developing methods for multiple harvests from the same growing material

Background

Ganoderma lucidum is a rare medicinal mushroom used for centuries in China due to its health-promoting properties. While most edible mushrooms can produce qualified fruiting bodies at least twice under proper conditions, G. lucidum tends to produce defective fruits after the first harvest, known as successive cropping obstacles. This occurs despite sufficient remaining nutrients in the growth substrate. The cause of this obstacle has been unclear, though environmental conditions and nutrient availability have been considered factors.

Objective

This study aimed to investigate the metabolite profile of G. lucidum using nontargeted metabonomic technology to understand the role of organic acids in cropping obstacles. The research focused on analyzing changes in organic acids at different growth stages and determining their potential role in autotoxicity feedback mechanisms that may prevent successful secondary fruiting.

Results

The study found significant pH decreases in growth substrates during cultivation, particularly before spore ejection. Metabolomic analysis revealed 724 organic acids and derivatives among 3521 total metabolites, with 194 showing significant differences between cultivars. Most differential organic acids were upregulated in both cultivars, consistent with observed pH decreases. Five specific acids were significantly upregulated in both cultivars across both MS modes. KEGG analysis showed most differential acids participated in metabolic pathways, with some involved in purine metabolism and microbial metabolism.

Conclusion

The research demonstrated that G. lucidum secretes organic acids into the growth substrate, leading to pH changes and potential autotoxicity feedback that inhibits secondary fruiting. This organic acid stress appears to be a key factor in successive cropping obstacles. Understanding this mechanism could help improve substrate utilization and cultivation efficiency of this valuable medicinal mushroom.
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