Analysis Of Habitat Factors And Mycorrhizal Microbial Diversity Of Russula Griseocarnosa

Russula griseocarnosa is an ectomycorrhizal(ECM)fungus,whose sporocarps have high economic value and cannot be cultivated artificially at present.Information of the growing habitat conditions of this species in natural forests including climate,vegetation,soil characteristics,and cooccurring rhizosphere microorganisms is useful for increasing the products of sporocarps of R.griseocarnosa by managing the natural forests and developing artificial cultivation technique.Therefore,in this study,we investigated the growing conditions of R.griseocarnosa in Taoyuan Town,Datian County,a major producing region of sporocarps of R.griseocarnosa in Fujian province.The main research results were as follows:1.In 2018 and 2019,the climate conditions in the fruiting period of R.griseocarnosa were investigated and analyzed in Taoyuan Town,Datian County.The results showed that the product of mushrooms in 2018 was significantly higher than that in 2019.The temperatures during two fruiting periods(from late June to early July and from late August to early September)in 2018 and 2019 were similar(about 25℃).In the first fruiting period from late June to early July,the precipitation in 2018(40.3mm)was significantly lower than that in 2019(293mm),while in the second fruiting period from late August to early September,the precipitation in 2018(170mm)was significantly higher than that in 2019(80.1 mm).The results suggest that the suitable temperature for sporocarp growth of R.griseocarnosa is 25℃ and the precipitation during the fruiting period may impact on the products of sporocarps of R.griseocarnosa.2.The vegetation and geographic characteristics were investigated in11 fruiting and 1 unfruiting stands in Taoyuan Town,Datian County.The results indicate that the suitable conditions for the growth of sporocarps of R.griseocarnosa were as follows: slope,19° ～ 41°;elevation,580 ～ 800m;canopy density,0.70 ～ 0.81;thickness of humus and litter layer,2.0-4.9cm;p H of soils,4.26 ～ 4.30;total carbon and potassium contents of soils were 26.3 ～ 26.7g/kg and 2.29 ～ 2.54g/kg,respectively.The vegetations belonged to natural and secondary forests with Fagaceae(Castanopsis carlesii,C.chinensis Hance,C.fargesii Franch.,C.sclerophylla(Lindl.)Schott.)as the dominant tree species(> 58%).The undergrowth vegetation were mainly,shrubs: the seedlings of Fagaceae trees,Ardisia japonica,Symplocos sumuntia,Smilax glabra,etc.;herbs: carex,ferns,indocalamus,etc.vines: Smilax china,Spatholobi caulis,Akebi aquinata,etc.The vegetations between fruiting and unfruiting stands in Taoyuan Town,Datian Country were not significantly different.However,the content of total carbon and organics in the soils of unfruiting stand was significantly higher than that in the fruiting stand.Therefore,decreasing the amount of humus and litter on soil surface may be effective for increasing the yield of sporocaps of R.griseocarnosa.3.The fungus community within the fruiting and unfruiting stands were investigated by metagenomic analysis using Illumina Hi Seq sequencing.During three periods of before,during and after fruiting,the root samples of underground and outside(1 m)sporocarps of R.griseocarnosa within a fruiting stand and the root samples within a unfruiting stand were separately collected.The results showed that the dominant fungi in all samples at phylum and genera were Basidiomycota and Ascomycota,and Lactarius and Russula,respectively.There was no significant difference in the fungus diversity between the fruiting and unfruiting stands,but the species diversity of fungi in underground roots of the sporocarps was significantly higher than those in the roots outside of the sporocarps and the unfruiting stand during fruiting.The LEf Se analysis showed that the co-occurring fungi beneath the sporocarps of R.griseocarnosa were mainly Tomentella and Cordyceps.The correlation analysis also showed that the co-occurring mycorrhizal roots of Tomentella and Cordyceps increased the growth of the mycorrhizal roots of Russula.These results indicate that Lactarius,Tomentella,and Cordyceps may be the mutual fungi for Russula.Besides,the RDA analysis indicated that the soils containing relative high nitrogen and potassium,low phosphorus and organics might be suitable for the growth of Russula in Taoyuan Town,Datian County.4.The bacterial community was investigated on three mycorrhizal root tips of R.griseocarnosa,Lactarius sp and Sebacina sp beneath and outside the sporocarps of R.griseocarnosa during the fruiting period in a C.carlesii forest.The results showed that in the mycorrhizal root tips of three ECM fungi in C.carlesii,the dominant bacteria at phylum were Cyanobacteria,Proteobacteria,Actinobacteria,Bacteroidetes and Firmicutes,and the dominant bacteria at genera were Acidothermus and Bradyrhizobium.The alpha diversity analysis showed that there was no significant difference in bacterial diversity among the mycorrhiza root tips of three ECM fungi beneath and outside of the sporocarps of R.griseocarnosa.However,the LEf Se analysis showed that there were significant differences of the abundance of special bacteria within the mycorrhizal root tips of three ECM fungi.Acidobacteria and Chloroflexi were specific in the mycorrhizal roots of R,griseocarnosa,while Streptomyces,Dinghuibacter and Actinoplanes were specific in the mycorrhizal roots of Sebacina sp.Besides,Rhizooiaceae and Bradyrhizobium were specific in the mycorrhizal roots beneath the sporocarps of R.griseocarnosa.Furthermore,the KEGG enrichment analysis showed that the major metabolic functions of these special different bacteria were mainly involved in the pathways regulating the metabolisms of carbohydrate and amino acid.