摘要:为探究农田土壤中真菌群落在时间序列对铬胁迫的响应机制及演变特征, 本研究以种植‘晋谷21号’谷子的土壤 (偏碱性的褐土) 为试验材料, 并在铬处理 (1 mmol?L?1 Cr6+) 前 (CK) 及处理后6 h (Cr_6 h) 与6 d (Cr_6 d) 分别取样, 通过高通量测序及数据统计分析, 探究农田土壤中真菌群落在铬胁迫时间序列上的响应机制、群落构建驱动机制及功能预测分析。结果表明, 铬胁迫时间序列上, 农田土壤中真菌群落的组成结构差异显著, α多样性中的Shannon指数在Cr_6 d阶段显著下降 (CK为4.17、 Cr_6 h为3.81, Cr_6 d为3.23); 土壤中真菌群落的构建主要由随机过程主导 (beta NTI: ?0.16, ?0.71, ?0.23); 且随铬胁迫时间增长, 群落分布更加广泛(迁移率m: CK为0.066、Cr_6 h为0.132、Cr_6 d为0.163), 即迁移率增大, 种间关系以共生为主, 赤霉菌属、镰刀菌属、金孢子菌属等是共生网络中的关键菌种; 功能预测分析表明铬胁迫时间序列上土壤中真菌群落以病原、腐生营养型为主, 高丰度的镰刀菌属等表明土壤中可能存在病原菌污染。研究结果表明在铬胁迫时间序列上, 土壤中真菌群落组分及组成结构变化显著, 群落构建由随机过程主导且群落所受扩散限制减小, 共生网络的种间关系复杂化。本研究通过铬胁迫处理农田土壤, 模拟土壤微生物群落对胁迫的应激与反应过程, 对重金属污染土壤的治理修复及推动可持续农业发展具有重要意义。
关键词:铬胁迫/
时间序列/
土壤真菌群落/
群落组成与结构/
群落构建
Abstract:Heavy metal chromium (Cr) is one of China’s main soil pollutants and poses a great threat to its agricultural soils, especially in the Shanxi Province, where the soil Cr content is higher than the national average. A new millet (Setaria italica) variety, ‘Jingu 21’, has many advantages such as high quality, high yield and disease resistance. To investigate the changes and response mechanisms of fungal communities in agricultural soils during a period of Cr stress, we used soil (alkaline brown soil) planted with ‘Jingu 21’ as this study’s experimental material. Soil samples were taken before the introduction of Cr (CK), as well as 6 h (Cr_6 h) and 6 d (Cr_6 d) after 1 mmol L?1 of Cr6+ was introduced to the soil. High-throughput sequencing and statistical analysis of the data were used to investigate the response mechanism, the soil fungal community establishment, and the functional prediction of fungal communities in ‘Jingu 21’ soils during the period of Cr stress. The spatial and temporal distribution patterns of soil fungal communities were investigated using the non-metric multidimensional scale analysis, the soil fungal community establishment driving mechanism was investigated by constructing an interspecific symbiotic network diagram and a neutral community model (NCM), and the changes in soil fungal community function were investigated using FUNGuild. The results revealed that the composition and structure of soil fungal communities differed significantly at the phylum and genus levels during the period of Cr stress, and the Shannon diversity index of the community decreased significantly (P<0.05) at the Cr_6 d stage (4.17 for CK, 3.81 for Cr_6 h, and 3.23 for Cr_6 d). The spatial and temporal distribution patterns of fungal communities were similar within the same Cr stress period and differed significantly across these periods. The fungal community establishment was dominated by stochastic process (beta NTI: ?0.16 for CK, ?0.71 for Cr_6 h, and ?0.23 for Cr_6 d). The interspecific symbiotic network analysis revealed that the fungal species were mostly positively correlated with each other; the interspecific symbiotic network of the Cr_6 d stage had a higher number of edges, average degree, and average path length than those of the CK and Cr_6 h stages, indicating that the community was more stable in the Cr_6 d stage than in the CK and Cr_6 h stage. Gibberella, Fusarium, and Chrysosporium were the key genera in the network diagram. The NCM quantified the stochastic processes further indicated that the soil fungal community was widely distributed (migration rate m: 0.066 for CK, 0.132 for Cr_6 h, and 0.163 for Cr_6 d). The FUNGuild function prediction showed that the soil fungal community was dominated by pathogenic and saprophytic trophic types. In addition, the abundance of sensitive bacteria, such as Mortierella and Gibberella, decreased, and the abundance of resistant bacteria, such as Fusarium, increased, indicating that Cr stress may affected the abundance of sensitive and resistant fungi in the soil, with the highest abundance of Fusarium indicating possible soil contamination with pathogenic bacteria. Ultimately, the results of this study revealed that the fungal community in soil planted with ‘Jingu 21’ changed significantly during a period of Cr stress; the soil fungal community establishment was dominated by stochastic processes; the diffusion restrictions of the community gradually decreased; and the interspecific relationships were complex and primarily symbiotic. In conclusion, herein, we simulated the stress response of soil microbial communities to Cr stress by treating agricultural soils with Cr6+. In addition, we demonstrated the response mechanism of soil fungal communities during a period of Cr stress, which is an important consideration for the treatment and remediation of heavy metal-contaminated soils and the promotion of sustainable agricultural development.
Key words:Chromium stress/
Stress time/
Fungus community/
Community composition and structure/
Community construction
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