枯草芽孢杆菌菌剂不同施用方式对甜瓜土壤微生物多样性及生长的影响

Effects of different application methods of Bacillus subtilis agent on soil microbial diversity and growth of muskmelon

摘要:

甜瓜连作种植和化学肥料过量施用造成了土壤微生态环境失衡、病害严重和产量降低等问题。施用枯草芽孢杆菌菌剂是改善土壤微生态环境、防治土传病害、促进植物生长的一项重要措施。文中以枯草芽孢杆菌为试验菌剂，分析菌剂不同施用方式对设施甜瓜土壤微生物多样性及生长的影响，采用稀释涂布平板方法测定土壤中可培养微生物的数量，采用Illumina Miseq测序技术测定土壤未培养微生物多样性，采用称重法测定甜瓜产量。结果表明，不同甜瓜生育时期，灌根、穴施和蘸根3种菌剂施用方式处理土壤可培养细菌的数量均显著高于对照，灌根、穴施和蘸根处理之间不存在显著差异；3个菌剂施用方式处理开花期土壤真菌数量显著低于对照，但是拉秧期土壤真菌数量差异不显著。比较3种菌剂施用处理中未培养微生物的多样性发现，细菌Shannon指数均高于常规施肥对照，Simpson指数低于对照；蘸根处理的真菌Shannon指数最低，Simpson指数最高。NMDS和聚类分析发现枯草芽孢杆菌菌剂蘸根施用处理对土壤中细菌和真菌菌群影响较大，均独立于一个分枝。微生物菌剂的施用使拟杆菌门 (Bacteroidetes) 的丰度显著降低，放线菌门 (Actinobacteria) 和酸杆菌门 (Acidobacteria) 的丰度显著升高，其中以蘸根处理变化最大。菌剂处理对真菌菌群的多样性影响较小，仅对壶菌门 (Chytridiomycota) 的丰度有显著影响。施用枯草芽孢杆菌菌剂可增加甜瓜的株高、茎粗、叶面积，蘸根处理的促长、增产效果最为显著。枯草芽孢杆菌菌剂作为一种新型环保肥料，具有增加土壤可培养微生物数量、提高土壤微生物多样性、促长增产的作用，该研究为枯草芽孢杆菌菌剂的合理施用提供了科学依据。

Abstract:

Continuous planting of muskmelon and excessive application of chemical fertilizers have caused a series of problems, such as imbalance of the soil micro-ecological environment, serious soil-borne diseases and yield loss. Application of Bacillus subtilis agent is an important way to improve soil micro-ecological environment, prevent soil-borne diseases, and promote plant growth. In this study, B. subtilis was used as experimental agent to analyze the effects of different application methods on the soil microbial diversity and growth of muskmelon in greenhouse. The number of culturable microorganisms in soil was measured by dilution-plate method. The diversity of soil uncultivated microorganisms was determined by Illumina Miseq sequencing technology. The yield of muskmelon was measured by weighing method. The number of culturable bacteria in the root irrigation, hole application and dipping root application groups was higher than that of the control in different muskmelon growth stages, but there was no significant difference among the three different application methods. The number of soil fungi from B. subtilis agent treatment groups in flowering stage was significantly lower in comparison to the control group. However, B. subtilis agent treatment did not cause significant difference on soil fungi number at the fruiting and pulling stage. Diversity analysis of uncultured microorganisms showed that the Shannon index values of bacteria were higher and Simpson index values were lower respectively in the three B. subtilis treatment groups than that in the control. Moreover, the dipping root treatment produced the lowest Shannon index value and the highest Simpson index value of fungi. NMDS and cluster analysis showed that B. subtilis agents dipping root treatment significantly affected the bacterial and fungal flora, both of which were clustered into one independent branch. The application of B. subtilis agents, especially dipping root treatment, significantly decreased the abundance of Bacteroidetes, increased the abundance of Actinobacteria and Acidobacteria. The B. subtilis agent treatment didn’t produce significant effect on the diversity of fungal flora except Chytridiomycota. The height, stem diameter and leaf area of muskmelon increased by applying B. subtilis agents, and dipping root treatment produced the most significant effect. As a new type of environmental protection fertilizer, B. subtilis agent can increase the number of soil culturable microorganisms, improve soil microbial diversity, and promote growth and yield. This study would provide a scientific basis for the rational application of B. subtilis.