The taxonomy, ecology and bioactive properties of South-East Queensland russulaceae

The taxonomy, ecology and bioactive properties of South-East
Queensland russulaceae

The Russulaceae are a cosmopolitan family of basidiomycetous fungi. They have great ecological importance as ectomycorrhizas, forming mutualistic associations with a large number of plant species. The family also includes edible species, and species possessing bioactive secondary metabolites.

Southeast Queensland (SEQ), Australia has a diverse geography, supporting a significant biodiversity, which includes Russulaceae fungi. However, few formal studies have been conducted on this group in the region, leaving many taxa undescribed or poorly documented, a situation that needs to be addressed.

Morphologically, members of the two main genera, Russula and Lactarius, are readily identifiable in the field, however the determination of species is difficult. Microscopic examination may improve species diagnosis, but the results are often inconclusive or incorrect. Therefore molecular taxonomy was utilised to collect additional information from specimens collected from 23 sites within SEQ so as to identify known and unknown species.

From the 149 specimens genetically studied, 94 sequences of the basidiomycete-ITS region were obtained. 15 of these sequences were considered to be identical to sequences held in GenBank, the majority of these being Australian. Another two were from an order unrelated to this study. However, it was revealed the remaining 83 sequences were potentially members of up to 33 new species. Four new taxa which contained the highest number of collected specimens, were subsequently described using both molecular and morphological taxonomic approaches.

Russulaceae species are known to associate with Australian obligate mycoheterotrophic orchids. To further document the Russulaceae of SEQ, the fungi that associate with roots of the orchid, Dipodium roseum were investigated for the first time. Both Sanger and Next Generation sequencing of extracted and amplified DNA showed the presence of both Russula and Lactarius spp, in roots of plants. This is the first time Lactarius spp. have been identified as mycobionts in an Australian orchid and this may have conservation implications for threatened species within the Dipodium genus.

As the development of antimicrobial resistance and rates of cancer continue to be of societal concern, there is a need to continue the search for new or more effective drugs. Bioactive metabolites produced in nature are one of the most extensive sources of these compounds, and it has been shown species of the Russulaceae produce antioxidant, anticancer and antimicrobial compounds. This study provided the opportunity for investigation of the bioactive properties of some of the new Russulaceae specimens obtained.

Although extracts of the Russula fungi obtained here had little antimicrobial activity there was some impact on the growth of the two cancer cell lines studied which warrants further study.

This study has thus shown that the SEQ region in Australia contains a substantial number of undescribed Russulaceae fungi. Further investigation of these taxa may reveal additional novel aspects of Australian ecosystem functioning as well as potentially provide useful bioactive compounds for humankind.