Diversity And Heavy Metal Tolerance Of Endophytic Fungi From Dysphania Ambrosioides,A Hyperaccumulator From Pb-Zn Contaminated Soils

Microbial-assisted phytoremediation is being explored to remediate heavy metal?HM?contaminated soils for its benificial characteristics.To understand the community structure and the possible ecological role of fungal endophytes?EF?associated with Dysphania ambrosioide,the diversity and heavy metal tolerance of EF associated with D.ambrosioides,a hyperaccumulator collected from two Pb-Zn contaminated sites were investigated with culture-depend and culture-independent approaches in the present study.The results showed that total of 237 culturable EF were isolated from 368 shoots and roots segments and identified to 43 taxa based on morphological characteristics and 18s rDNA ITS analysis.The total colonization rate?CR?of EF of plants growing in the slag heap?35.20%?was significantly lower than that of plants growing in the wasteland?57.67%??P<0.05,chi-squared test?.The dominant genera of D.ambrosioides growing in the slag heap were Plectosphaerella sp.,Cladosporium sp.2,and Verticillium sp.,and their relative frequency?RFs?were 18.07%,10.84%,and 8.43%,respectively;while,the dominant genera of fungi from the wasteland were Phoma sp.,Peyronellaea sp.,and Alternaria sp.,and their RFs were 20.13%,12.34%,and 11.69%,respectively.The two sampling sites were only 2 km away from each other and the environmental conditions at both sites were similar,but the CR,dominant genera as well as the community structure of EF from the two sites were significantly different.We suggest that the difference may result from differences in soil HM and water content in two sites:the higher HM content and lower water content in the soil,the fewer microorganisms in the soil and thus the lower CRs of endophytes in the plant.HM tolerance tests indicated that 50%of the tested isolates exhibited HM tolerance capacity.However,only three isolate exhibited better HM tolerance:FT2G59?Penicillium sp.?could tolerate Pb,Zn,and Cd simultaneously,and their MICs were 30-50 mmol/1,>680 mmol/1,20-30 mmol/1,respectively,and its metal tolerance was better than other reported Penicillium sp.;the other two isolate FT2G7?Phomopsis columnaris?and FT2G1?Phomopsis columnaris?exhibited better metal tolerance to Cd,and their MICs were 30-50 mmol/1.The culture-independent analysis indicated that the dominant genera of D.ambrosioides shoots from the slag heap were Erysiphe sp.,Lecanicilium muscarium Aspergillus flavus,Pleurotus sp.,Leucosporidum golubevii,Coniothyrium cereal,Mucor spp.?Mucor cicinelloides,Mucor sp.?BEA₂010??,and the dominant genera of roots from the slag heap were Aureobasidium pullulans,Phomopsis columnaris,Holtermannia comiformis,Pseudogymnoascus roseus,Skeletocutis diluta,Cryptococcus spp.?Cryptococcus bhutanensis,Cryptococcus albidus?.While,the dominant genera of D.ambrosioides shoots from the wasteland were Cryptococcus spp.?Cryptococcus sp.?QMW₂009a?,Cryptococcus dimennae,Cryptococcus victoriae,Cryptococcus oeirensis,Cryptococcus laurentii,Cryptococcus flavus?,Filobasidium floriforme and Dioszegia zasoltii var,and the dominant genus of roots from the wasteland was Purpureocillium lilacinum.The dominant genera as well as the community structure of EF from the two sites were significantly different both in culture-depend and culture-independent results.The difference may due to the different HM concentration in samples.