连作与轮作谷子根际土壤真菌群落分布特征

Distribution characteristics of the soil fungi community in the rhizosphere of foxtail millet under different planting patterns

  • 摘要: 为了解谷子连作对土壤真菌群落结构的影响, 以撂荒地为对照, 以谷子-玉米轮作、谷子连作3年、连作5年根际土壤为研究对象, 采用真菌ITS高通量测序技术, 探究不同种植模式下谷子土壤真菌群落分布特征。结果表明: 不同种植模式下, 谷子根际土壤共检测到真菌10门24纲46目79科136属和146种。在门和纲水平上群体结构相对稳定, 谷子田土壤优势门主要包括子囊菌门和担子菌门, 优势纲为粪壳菌纲、座囊菌纲和盘菌纲。在目水平谷子根际土壤粪壳菌目相对丰度是撂荒地的2倍以上; 在科水平和属水平轮作土壤被孢霉、球腔菌相对丰度高于连作土壤, 链格孢菌、亚隔孢壳菌和粉红螺旋聚孢霉菌相对丰度低于连作土壤。Alpha多样性分析显示, 谷子-玉米轮作与谷子连作根际土壤真菌丰度差异达显著水平(P<0.05), 轮作土壤真菌丰度最高。Beta多样性分析显示连作3年和连作5年根际土壤真菌结构相似, 与撂荒地以及轮作根际土壤真菌结构存在差异, 表明不同种植模式谷子根际土壤真菌群落结构发生了改变。相关性分析显示, 碱解氮与有机质呈极显著正相关(P<0.01), 与有效磷、脲酶活性呈显著相关(P<0.05), 多酚氧化酶活性与速效钾呈显著正相关(P<0.05), 真菌群落的Chao1指数、Observed species指数与多酚氧化酶活性呈极显著正相关(P<0.01)。冗余分析(RDA)表明, 撂荒地受毛壳菌影响, 轮作受球腔菌属和微结节霉属的影响, 连作3年和连作5年受毛葡孢属、毛喙壳属、亚隔孢壳属等影响。LEfSe分析确定了谷子根际土壤特定标志物, 轮作根际土壤的标志物包含被孢霉属和球腔菌属, 连作3年根际土壤标志物包含毛葡孢属、亚隔孢壳属和粉红螺旋聚孢霉属, 连作5年根际土壤标志物包含链格孢菌属和亚隔孢壳属。因此, 谷子-玉米轮作与谷子连作相比, 土壤真菌群落结构差异较大, 轮作土壤腐生菌较多, 连作土壤病原菌较多。

     

    Abstract: Continuous cropping obstacles occur in foxtail millet. To understand the effects of continuous cropping of foxtail millet on the soil fungal community structure, we explored the distribution characteristics of the fungal community of the rhizosphere soil using the fungal ITS high-throughput sequencing technology under different cropping strategies, including foxtail millet-maize rotation, foxtail millet continuous cropping for three years and five years, and the abandoned land taken as a control. The results showed that a total of ten phyla, 24 classes, 46 orders, 79 families, 136 genera, and 146 species of fungi were detected in the rhizosphere soil of foxtail millet under different cropping strategies. The population structure was relatively stable at the phylum and class levels. The dominant phyla in the soil mainly consisted of Ascomycota and Basidiomycota, whereas the dominant classes were Sordariomycetes, Dothideomycetes, and Pezizomycetes. At the order level, the relative abundance of Sordariales in the rhizosphere of foxtail millet was two times greater than that in abandoned land. At the family and genus levels, the relative abundance of Mortierellaceae and Mycosphaerellaceae was higher, whereas the relative abundance of Alternaria, Didymella, and Clonostachys was lower in the rotation soil than in the continuous cropping soil. Alpha diversity analysis showed that the fungal abundance of the rhizosphere soil was significantly different under foxtail millet-maize rotation and foxtail millet continuous cropping (P<0.05), and that under that rotation, soil diversity was the highest. Beta diversity analysis revealed that the fungal structures of the rhizosphere soil under continuous cropping for three and five years were similar, and they were different from those under abandoned land or rotating cropping, indicating that the fungal community structure in the rhizosphere soil of foxtail millet changed under different cropping strategies. Correlation analysis showed that alkali-hydrolyzed nitrogen was significantly positively correlated with organic matter (P<0.01) and significantly correlated with available phosphorus and urease activities (P<0.05), while the activity of polyphenol oxidase was positively correlated with available potassium (P<0.05) and significantly positively correlated with the Chao1 index and the observed species index (P<0.01). Redundancy analysis (RDA) indicated that CK were affected by Chaetomium, CR was affected by Mycosphaerella and Microdochium, TC and FC were affected by Botryotrichum, Chaetomidium, and Didymella. LEfSe analysis identified distinctly specific markers in the rhizosphere soil of foxtail millet under different cropping strategies. The markers of rhizosphere soil contained Mortierella and Mycosphaerella for the rotating cropping, Botryotrichum, Didymella, and Clonostachys for three years of continuous cropping, and Alternaria and Didymella for five years of continuous cropping. Overall, the soil fungal community structure under millet-maize rotation cropping, exhibiting more saprophytic fungi and fewer pathogenic fungi, was significantly different from that under foxtail millet continuous cropping, which provided useful information for the study of the continuous cropping obstacles of foxtail millet.