棉秆炭调控对碱性镉污染水稻根际土壤真菌群落结构和功能的影响

Effects of Cotton Stalk Biochar on the Structure and Function of Fungi Community in Alkaline Rhizosphere Soil of Rice Under Cadmium Pollution

为研究棉秆炭对碱性镉污染水稻根际土壤真菌多样性、结构及功能的影响,采用室外水稻盆栽试验,在土壤中添加了0、1和8 mg·kg-1的镉和炭土质量比分别为0%、1%和5%的棉花秸秆生物质炭,以水稻成熟期根际土壤为研究对象,借助Illumina HiSeq高通量测序手段分析棉秆炭与镉污染条件对碱性水稻根际土壤真菌群落多样性、结构及潜在功能的影响,探寻不同土壤环境因子与真菌群落结构间的关联性.结果表明:①施用棉秆炭显著提高了土壤pH、速效养分和有机质等指标,并降低土壤中可还原态镉的含量(P<0.05).②水稻根际土壤真菌菌门分布主要为子囊菌门、Aphelidiomycota门和壶菌门,占所有菌门的57%.菌属分布主要为被孢霉属、链格孢属和镰刀菌属.各处理间真菌群落α-多样性差异显著(P<0.05).未添加棉秆炭处理下(C0),镉浓度的增加降低了土壤中壶菌门、被孢霉属和链格孢属的相对丰度和真菌多样性指数(Shannon指数).在不同浓度镉处理下(Cd0、Cd1和Cd8),增加棉秆炭会降低真菌群落丰富度指数(Chao1指数)和Shannon指数.镉污染导致土壤中壶菌门相对丰度增多,却使子囊菌门丰度下降,施用棉秆炭可显著提升壶菌门的相对丰度(P<0.05).镉污染使被孢霉属和链格孢属丰度下降,但是施用棉秆炭可使链格孢属相对丰度增多.增加棉杆炭施用量,土壤中会存在更多的内生菌、植物病原体和腐生菌;而镉污染程度增加会减少土壤中内生菌、植物病原体和腐生菌.③影响真菌群落多样性及结构的主要环境因子有土壤速效钾、有机质和pH.水稻土壤镉含量中占比最大的可还原态镉与轮形动物门、Aphelidiomycota门和子囊菌门呈显著正相关(P<0.05),但与其它菌门呈负相关(P<0.05).研究结果说明棉秆炭在碱性镉污染土壤微生态调控方面具有一定的作用.

To study the effects of cotton stalk biochar on the regulation of fungal diversity,the structure and function of alkaline rice rhizosphere soil under cadmium pollution was investigated.An outdoor pot experiment was conducted by adding cotton stalk biochar(0%,1%,and 5%)to an alkaline paddy soil with a cadmium concentration of 0.1 and 8 mg·kg-1.Taking rice rhizosphere soil as the research object,Illumina HiSeq sequencing was used to analyze the effects of cotton stalk biochar and cadmium pollution on the diversity,structure,abundance,and function of fungi in an alkaline rhizosphere soil,and to explore the correlation between soil environmental factors and the fungal community under the control of cotton stalk biochar.The results showed that:①the application of cotton stalk biochar significantly increased the soil pH,available nutrients,and organic matter,and reduced the content of reducible cadmium in the soil(P<0.05).②The distribution of rice rhizosphere soil fungi was mainly Ascomycota,Aphelidiomycota,and Chytridiomycota,which accounted for 57%of all mycophytes.The genus was mainly Mortierella,Alternaria,and Fusarium.There was a significant difference in theα-diversity of the fungal community among the treatments(P<0.05).In the absence of cotton stalk biochar(C0),the increase in the cadmium concentration reduced the relative abundance and fungal diversity index(Shannon index)of Chytridiomycota,Mortierella,and Alternaria in the soil.Under different concentrations of cadmium(Cd0,Cd1,and Cd8),increasing cotton stalk biochar reduced the fungal community richness index(Chao1 index)and Shannon index.Cadmium pollution resulted in an increase in the relative abundance of Chytridiomycota in the soil,but decreased the abundance of Alternaria.The application of cotton stalk biochar could significantly increase the relative abundance of Chytridiomycota(P<0.05).Cadmium pollution reduced the abundance of Mortierella and Alternaria,but the application of cotton stalk biochar could increase the relative abundance of Alternaria.Increasing cotton stalk biochar means that soil will have more endophytes,plant pathogens,and saprophytes;while increasing cadmium pollution will reduce endophytes,plant pathogens,and saprophytes in the soil.③The main environmental factors affecting the diversity and structure of fungal communities are the available potassium,organic matter,and pH of the soil.The reducible cadmium content,which comprises the largest proportion of cadmium in rice soil,was significantly positively correlated to Rotifera,Aphelidiomycota,and Ascomycota(P<0.05),but negatively correlated to other mycophytes(P<0.05).The results indicate that cotton stalk biochar plays a certain role in the microecological regulation of alkaline cadmium-contaminated soil.