Correction: Influence of different irrigation methods on the alfalfa rhizosphere soil fungal communities in an arid region.

[This corrects the article DOI: 10.1371/journal.pone.0268175.].

Application potential of Vaccinium ashei R. for cadmium migration retention in the mining area soil.

Despite numerous reports on phytoremediation of heavy metals contaminated soil, there are few reports on plant retention of heavy metals in the mining area slope. This study was the first of its kind to explore the cadmium (Cd) retention capacity of the blueberry (Vaccinium ashei Reade). Firstly, we investigated the stress response of blueberry to different soil Cd concentrations (1, 5, 10, 15, 20 mg/kg) to assess its potential for phytoremediation by pot experiments. The results showed that the blueberry biomass exposed to 10 and 15 mg/kg Cd was significantly increased compared with the control (1 mg/kg Cd); the blueberry crown increased by 0.40% and 0.34% in 10 and 15 mg/kg Cd-contaminated soil, respectively, compared with control; the blueberry heigh did not even change significantly in each treatment group; the total chlorophyll content, peroxidase and catalase activity of blueberry were enhanced in 5-20 mg/kg Cd treatments. Furthermore, the Cd contents of blueberry in the root, stem and leaf increased significantly as the Cd concentration of soil increased. We found that more Cd accumulated in blueberry root: the bioaccumulation concentration factor was root > stem > leaf for all groups; the residual-Cd (Cd speciation) in soil increased by 3.83%-411.11% in blueberry-planted versus unplanted groups; blueberry improved the Cd-contaminated soil micro-ecological environment including soil organic matter, available K and P, as well as microbial communities. Then, to investigate the effect of blueberry cultivation on Cd migration, we developed a bioretention model and revealed that soil Cd transport along the model slope was significantly weakened by blueberry cultivation, especially at the bottom of the model. In a word, this research suggests a promising method for the phytoremediation of Cd-contaminated soil and the reduction of Cd migration in mining areas.

Potential of Miscanthus floridulus associated with endophytic bacterium Bacillus cereus BL4 to remediate cadmium contaminated soil.

Phytoremediation assisted by endophytic bacteria is promising to efficiently remediate cadmium (Cd) contaminated soil. Bacillus cereus BL4, isolated from Miscanthus floridulus growing around a pyrite mine, exhibited high Cd tolerance and plant growth-promoting traits and could improve Cd bioavailability in soil. As a result of the pot experiment, after inoculation with strain BL4, the fresh weight, height, and Cd accumulation of Miscanthus floridulus shoots increased by 19.08-32.26 %, 6.02-16.60 %, and 23.67 %-24.88 %, respectively, and roots increased by 49.38-56.41 %, 22.87-33.93 %, and 28.51 %-42.37 %, respectively. Under Cd stress, the chlorophyll content, photosynthetic rate, and root activity of Miscanthus floridulus increased, while the membrane permeability and malonaldehyde (MDA) content significantly decreased after the inoculation of BL4, which indicated the alleviation of the cytotoxicity of Cd. Accordingly, the glutathione (GSH) content increased, and the activities of antioxidant enzymes presented downward trends after BL4 inoculation. Cd bioavailability in soil increased after BL4 inoculation, accompanied by increases in the activities of soil enzymes (invertase, urease, alkaline phosphatase, dehydrogenase, FDA hydrolase, and catalase) as well as the richness and diversity of soil bacteria. Our findings revealed that strain BL4 might strengthen the phytoremediation of Cd by Miscanthus floridulus through its effects on plant physio-biochemistry and soil microecology, which provided a basis for the relative application to Cd-contaminated soil.

Effect of slow-released biomass alkaline amendments oyster shell on microecology in acidic heavy metal contaminated paddy soils.

Soil ecosystem functions and microbial community structure were severely impaired with long-term cadmium (Cd) contamination and acidification. To investigate the effect of amendments on soil physiochemical parameters and soil micro-ecology in acidic Cd contaminated soil, this study was conducted in a pot experiment with the application of calcium amendments, oyster shell powders (OS) and limestone (LM). Each amendment applied at ratios of 1.0%, 3.0%, and 5.0% (w/w), respectively. The results showed that the application of amendments increased the soil pH by 2.10-2.88, the bioavailable Cd decreased by 12.49%-19.48%, and un-bioavailable Cd increased by 96.57%-200.7%. The OS increased the richness index (Chao and Ace increased by 13.23%-16.20% and 7.13%-47.63%), and LM increased the microbial diversity index (Shannon increased by 1.14%-8.72% and Simpson indexes decreased by 28.00%-63.61%). In LM groups, soil microbial communities were significantly altered with increasing application concentrations, the relative abundance of phylum Proteobacteria, Bacteroidota and Gemmatimonadota increased, while Firmicute, Actinobacteria, Chloroflexi decreased. In OS treatments, the soil microbial community structure was basically unchanged. The correlation analysis showed that pH, TN, TP, CEC, OM were the dominant factors affecting the microbial community. This study has shown that application of amendments could effectively reduce the Cd bioavailability in soil, but LM altered the soil microbial community structure, while OS maintained the soil microbiological structure.

Influence of different irrigation methods on the alfalfa rhizosphere soil fungal communities in an arid region.

Xinjiang is the largest arid and saline agricultural region in China. The common irrigation methods in this area are traditional flood irrigation and drip irrigation. In this study, we investigated the effects of these two irrigation methods on the fungal diversity, community structures, and functions in alfalfa rhizosphere soil as well as the associated environmental factors in northern Tianshan Mountain (Xinjiang, China). Soil enzyme activities (urease and neutral phosphatase) were significantly higher in the drip-irrigated alfalfa rhizosphere soil than in the flood-irrigated alfalfa rhizosphere soil, whereas the fungal alpha diversity in the drip-irrigated alfalfa rhizosphere soil was significantly lower than that in the flood-irrigated alfalfa rhizosphere soil. Six dominant fungal phyla were identified (>0.1%), with Ascomycota being the most abundant in all soils, followed by Basidiomycota (5.47%), Mortierellomycota (1.07%), Glomeromycota (0.55%), Rozellomycota (0.27%), and Chytridiomycota (0.14%). Ascomycota and Glomeromycota species were significantly less abundant in drip-irrigated alfalfa rhizosphere soil than in flood-irrigated alfalfa rhizosphere soil. A LEFSe analysis identified Cladosporiaceae (20.8%) species as the most abundant marker fungi in drip-irrigated alfalfa rhizosphere soil. Of the 13 fungal functional groups identified on the basis of the functional annotation using the FUNGuild database, Ectomycorrhizal (22.29%) was the primary functional group. Compared with flood irrigation, drip irrigation significantly decreased the relative abundance of Ectomycorrhizal and Arbuscular_Mycorrhizal, while increasing the relative abundance of Plant_Pathogen, although not significantly (P = 0.19). Available potassium was revealed to be the main environmental factor influencing soil enzyme activities, fungal alpha diversity, fungal community structures, and fungal functions in response to the different irrigation methods. In conclusion, drip irrigation may be more appropriate than flood irrigation in the Tianshan dryland agricultural area for enhancing soil enzyme activities, but it may also increase the abundance of plant pathogenic fungi in the soil.

Mechanism underlying earthworm on the remediation of cadmium-contaminated soil.

Cadmium (Cd) contamination of soil becomes a potential agricultural and global environmental problem due to the need to ensure safe food. In this study, earthworms (Eisenia fetida) and plants (vetiver grass) were prepared for removal Cd from soil. The results showed the Cd concentration in the soil of all experimental groups decreased, notably by 17.60% in the group with 20 mg/kg Cd concentration. In the roots of vetiver, the content of Cd increased by 57% after earthworms were added and the transfer coefficient of Cd was also significantly increased. Moreover, Cd in the soil was generally absorbed by the intestinal tract of earthworms and became concentrated, mainly in the midgut and hindgut accounting for >77.78% of the total. In addition, enteric microorganism analysis demonstrated that the bacterial community structure played an important role in Cd enrichment and metabolism regulation. There was a significant correlation between some bacteria and Cd concentration. Among these bacteria, Pseudomonas brenneri, were involved in the adsorption and metabolism of Cd to reduce the toxicity of Cd to the earthworms. On the other hand, in order to cope with the external Cd stress, the malondialdehyde (MDA) and hydrogen critically (CAT) enzymes in the earthworms increased with the concentration. Therefore, the high tolerance of earthworms to Cd is related to its physiological adjustment and the balance of intestinal bacteria. The combination of earthworms, microorganisms and plants can result a good alternative to diminish the impact of Cd in soils.

Genetic diversity analysis of Hypsizygus marmoreus with target region amplification polymorphism.

Hypsizygus marmoreus is an industrialized edible mushroom. In the present paper, the genetic diversity among 20 strains collected from different places of China was evaluated by target region amplification polymorphism (TRAP) analysis; the common fragment of TRAPs was sequenced and analyzed. Six fixed primers were designed based on the analysis of H. marmoreus sequences from GenBank database. The genomic DNA extracted from H. marmoreus was amplified with 28 TRAP primer combinations, which generated 287 bands. The average of amplified bands per primer was 10.27 (mean polymorphism is 69.73%). The polymorphism information content (PIC) value for TRAPs ranged from 0.32 to 0.50 (mean PIC value per TRAP primer combination is 0.48), which indicated a medium level of polymorphism among the strains. A total of 36 sequences were obtained from TRAP amplification. Half of these sequences could encode the known or unknown proteins. According to the phylogenetic analysis based on TRAP result, the 20 strains of H. marmoreus were classified into two main groups.

[Comparative study on trace elements in Elsholtzia bodineri Vaniot. from Honghe by FAAS].

In the present paper, the authors prepared all the samples by the same method, and optimized the work conditions for flame qtomic absorption spectrometry. FAAS was applied to determine the trace elements, such as Pb, Cr, Cd, Cu, Zn, Hg, Se etc, in Elsholtzia bodineri Vaniot. from Mengzi, Shiping, Mile and Jianshui located in Honghe state. The method is simple, rapid and accurate, and allows simultaneous determination of many elements. The recoveries were in the range of 98.7%-116.4%, and RSD was 0.07%-1.69%. The contents of Pb, Cd and Hg were 53.47, 6.03 and 7.68 microg x g(-1), respectively, in the sample from Jianshui, and were higher than those from other areas. The content of Mn was the highest, and was higher in Mengzi than in other areas, and the average content in the four samples was 913.48 microg x g(-1), which was higher than the content in the soil. Fe is the semi-microelement whose average content in Elsholtzia bodineri Vaniot. from Honghe was 688.46 microg x g(-1), the high-to-low content sequence of Fe in terms of location was Mengzi, Mile, Shiping and Jianshui. The average content of Zn was 116.64 microg x g(-1), and the highest one was from Shiping. But we did not obtain the data of Se in the Elsholtzia bodineri Vaniot. from Honghe state by AAS, and did not detect Hg in samples from Shiping and Mile. The content of the detected elements in Mengzi's sample had the sequence as follows; Mn > Fe > Zn > Pb > Cu > Cr > Cd > Hg>Se, while the sequence was Mn > Fe > Zn > Pb > Cu > Hg > Cd > Cr > Se in the sample of Jianshui, Mn > Fe > Z n >Pb > Cu > Cd > Cr > Hg > Se in Shiping, and Fe > Mn > Zn > Pb > Cu > Cd > Cr > Hg > Se in Mile. The results show that the content of the trace elements is high, especially, Mn, Fe and Zn, in Elsholtzia bodineri Vaniot. in Honghe. Therefore, Elsholtzia bodineri Vaniot., which can be used as drug or beverage, is worth exploitation.