Unravelling the complex relationship between Suillus bovinus and Gomphidius roseus through investigation of their sporocarps in Pinus massoniana forests.

Abstract

Background: The co-occurrence of sporocarps has revealed many intimate associations between different ectomycorrhizal (ECM) fungi species. The co-occurrence of sporocarps of Suillus bovinus and Gomphidius roseus, two edible ECM fungi, is well recognized; however, the interactions between them remain largely unknown. This study investigated the relationship between these two fungi occurring in Pinus massoniana forests through phenological, microbiome, and metabolome analyses.

Results: Gomphidius roseus sporocarps were always found alongside sporocarps of S. bovinus, but not vice versa. The ECM associated with S. bovinus sporocarps exhibited a long-distance exploration type, whereas the ECM associated with G. roseus sporocarps formed a contact exploration type. Both S. bovinus and G. roseus sporocarps and ECM contained the mycelia of both fungi. In contrast, different fungal sporocarps and ECM were dominated by distinct bacterial species. Suillus bovinus sporocarps were recorded in all ages investigated, ranging from 1 to 5 years old to over 30 years old. In contrast, G. roseus sporocarps were mainly found in forests older than 10 years. Previous studies suggested that G. roseus parasitizes S. bovinus; however, the occurrence of G. roseus sporocarps did not significantly affect S. bovinus sporocarp production or P. massoniana growth, challenging this assumption. Despite their intimate interactions, the metabolic profiles of S. bovinus sporocarps more closely resembled those of S. luteus, not G. roseus.

Conclusion: Overall, our analyses showed both similarities and dissimilarities in phenology, microbiome, and metabolome features between the two fungi, and the genesis of G. roseus sporocarps is highly dependent on S. bovinus. These results further indicate that while the formation of ECM between G. roseus and the host may rely on ECM formed by S. bovinus and the same host, it is not parasitic.