Study On The Cadmium-rich Characteristics And Influencing Factors Of Boletus Griseus

In order to further analyze the cadmium(Cd)-rich problem of Boletus griseus,in this study,we collected fruit bodies which were B.griseus(HH)and non-B.griseus(NHH)of the Bolete family and their rhizosphere soil from the same growing period and the same place of origin,compared the differences in the mineral content levels of HH and NHH fruit bodies in the same growth period and in the same place of origin,compared the differences in mineral elements and physical and chemical properties of rhizosphere soil,and confirmed the cadmium-rich characteristics of HH.At the same time,in order to analyze the influencing factors of the cadmium-rich characteristics of HH,this study analyzed the differences of low molecular weight organic acids in HH and NHH fruit bodies,analyzed the diversity and differences of bacteria in the rhizosphere soil of HH and NHH.The main results are as follows:1.From July 29 th to August 7th,2019,Boletus griseus(HH)fruit bodies and rhizosphere soil substrate were collected in Dashanjiao Village,Pubei Township,Yimen County,Yunnan Province,and 24 samples were obtained.The NHH fruit bodies and their rhizosphere soil substrates from the same origin were collected,mainly including: B.edulis、B.bicolor、B.speciosus、B.aereus、Leccinum crocipodium、B.sinicus、Tylopilus eximius,a total of 49 samples.The crude ash content of HH was 5.40%-8.69%,which was significantly higher than that of NHH(3.20%-7.45%,t test,p<0.01).The Cd content of HH was 3.55mg/kg-23.66mg/kg,which was significantly higher than that of NHH(0.08mg/kg-2.63 mg/kg,t test,p<0.01);for other mineral elements,the average values of HH content were: Cr 5.92 mg/kg、Pb 1.91 mg/kg、Mn 36.73 mg/kg、Zn 122.78 mg/kg、Cu 37.80 mg/kg、Mg 1581.55 mg/kg、Fe 656.21 mg/kg、Na 133.61 mg/kg、K 3117.79 mg/kg 和 Ca 999.70 mg/kg;the average values of NHH content were: Cr 4.33 mg/kg、Pb 0.55 mg/kg、Mn 106.21 mg/kg、Zn 35.64mg/kg、Cu 29.72 mg/kg、Mg 1172.72 mg/kg、Fe 356.53 mg/kg、Na 132.24 mg/kg、K2598.78 mg/kg 和 Ca 550.96 mg/kg.It could be seen from the t test that,except for Mn and Na,the contents of all mineral elements of HH were significantly higher than that of NHH(p<0.01).The average content of various mineral elements in the rhizosphere soil of HH was: Cd0.52 mg/kg、Cr 17.54 mg/kg、Pb 56.97 mg/kg、Mn 0.73 mg/g、Zn 105.37 mg/kg、Cu114.76 mg/kg、Mg 6.19 mg/g、Fe 17.62 mg/g、Na 0.46 mg/g、K 1.64 mg/g 和 Ca 0.19mg/g,which the NHH was: Cd 0.53 mg/kg、Cr 14.89 mg/kg、Pb 71.34 mg/kg、Mn 1.13mg/g、Zn 139.29 mg/kg、Cu 98.93 mg/kg、Mg 6.60 mg/g、Fe 20.28 mg/g、Na 0.61 mg/g、K 1.55 mg/g 和 Ca 0.21 mg/g.It could be seen from the t test that the Cd content of HH rhizosphere soil was not different from NHH,but HH showed a very high bioconcentration coefficient for soil Cd,indicating that the Cd accumulation effect of B.griseus was the personality characteristics of this species of large fungus.2.On July 21,2020,the HH fruit body and the soil matrix of the rhizosphere were collected in Dashanjiao Village,Pubei Township,Yimen County,Yunnan Province,at the same time,five other NHH fruiting bodies and their rhizosphere soil substrates were collected,including B.edulis、B.bicolor、B.speciosus、B.aereus and Leccinum crocipodium.17 kinds of low molecular weight organic acids were detected in HH,among which citric acid(4.85 mg/g),succinic acid(0.14 mg/g)and fumaric acid(0.53 mg/g)were significantly higher than the other five NHH,and malic acid(5.50 mg/g)also expressed a higher content level.Analysis of 17 kinds of free amino acids showed that aspartic acid,threonine,serine,glutamic acid,alanine,valine,cysteine,tyrosine,lysine,histidine,and the content of proline was significantly higher than the other five kinds of NHH.High content of low-molecular-weight organic acids and free amino acids may be one of the important factors for the Cd enrichment of B.griseus.Bacterial genome experiments were performed on HH and five other NHH rhizosphere soils.Through the comparative analysis of metagenomics,it is found that the bacterial flora in the HH rhizosphere soil was low in Richness but high in Evenness;At the level of phylum classification,the phylum Proteobacteria,Myxococcus,and Bacteroides showed higher abundance,and those with lower abundance were Actinobacteria and Acidobacteria.At other classification levels,there was a higher abundance of γ-proteobacteria、Burkholderiaceae and Sphingomonas in HH rhizosphere soil.The COG annotations of the metagenomics of six bolete rhizosphere soil bacteria showed that,except for B.edulis,the annotation level of the metagenomics on inorganic ion transport and metabolism was significantly positively correlated with the Cd content of the bolete fruiting body(p<0.05).Based on this,it was speculated that there was a kind of recruiting effect on the functional bacteria with inorganic ion transport in rhizosphere soil with B.griseus,which may also be one of the important factors for B.griseus to accumulate Cd.