北方玉米田免耕及不同覆盖模式下土壤典型病原真菌丰度变化规律及其影响因素研究

Although no-tillage with maize stalk mulched has many advantages compared with conventional tillage, it can also increase the risk of soil-borne diseases. However, we know little about the changes of abundances of soil typical pathogenic fungi and its influencing factors under no-tillage with different residue patterns. This project use northern corn fields of no tillage with straw mulched as the study object. based on long-term experiment fields with different amount and frequency of straw mulched for 9 years, we will investigate the abundances changes of soil typical pathogenic fungi (Fusarium graminearum, Fusarium moniliforme, Rhizoctonia solani, Pythium inflatum and Pythium graminicola) under no-tillage with different residue patterns during different growth stages of maize by real-time PCR method, and then suggest the optimal amount and frequency of maize straw mulched; investigate soil microbial biomass, diversity and community structure by phospholipid fatty acids and high-throughput sequencing methods to reveal the main microbial factors influencing abundance changes of soil typical pathogenic fungi; detected physical and chemical parameters to reveal the key non-biological factors influencing abundance changes of soil typical pathogenic fungi. The results of the project will provide some guides for the rational application of no tillage with straw mulched and in situ improvement for the soil with high-disease risk.

尽管玉米免耕秸秆覆盖与传统耕作相比有许多优点，但也会带来土传病害加重的风险，而免耕不同覆盖模式下土壤典型病原真菌丰度变化规律及其影响因素还不清楚。项目以北方免耕秸秆覆盖玉米田为研究对象，以免耕秸秆覆盖长达9年具有不同秸秆覆盖量和覆盖频率的长期实验田为研究平台，通过荧光定量PCR方法，揭示免耕不同覆盖模式下，不同玉米生育期土壤典型病原真菌（F. graminearum，F. moniliforme，R. solani，P. inflatum，P. graminicola）丰度变化规律，筛选最优秸秆覆盖量和频率；通过磷脂脂肪酸和高通量测序方法，考察土壤微生物生物量，多样性和区系变化，揭示影响土壤典型病原真菌丰度变化的生物因素；通过土壤理化及养分指标测定，阐明影响土壤典型病原真菌丰度变化的非生物因素。项目的研究结果将对玉米免耕秸秆覆盖耕作方式的合理应用及高病害风险土壤的原位调控具有重要指导意义。

秸秆覆盖已经成为一项重要的保护性耕作技术，但其对土壤微生物的影响，特别是对土传病原真菌的影响还所知甚少。本项目以北方免耕秸秆覆盖玉米田为研究对象，考察不同秸秆覆盖量（0，33%，67%，100%覆盖量）和覆盖频率（每三年覆盖0次，1次，2次和3次）对典型土传病原真菌数量的影响规律并阐明影响病原菌数量变化的生物和非生物因素。研究表明，不同秸秆覆盖处理可明显增加土壤玉米茎腐病（根腐病）病原菌Fusarium graminearum和Fusarium moniliforme的数量，但对Rhizoctonia solani， Pythium inflatum，Pythium graminicola三个病原真菌的数量无明显影响。在各覆盖处理中，33%和100%覆盖量及3还0和3还3覆盖频率处理可能会引起较大的病害爆发风险。相比传统耕作，秸秆覆盖可增加土壤AM真菌，真菌，革兰氏阴性细菌生物量，但降低放线菌和革兰氏阳性菌生物量。在种群构成上，覆盖处理可显著增加Proteobacteria，Bacteroidetes，Basidiomycete和Zygomycota的相对丰度，但降低了Actinobacteria，Chloroflexi，Nitrospirae和Ascomycota的相对丰度。相关分析表明，F. graminearum与细菌属Nitrospira, Opitutus，真菌属Nectria, Fusarium, Acremonium, Leptosphaeria，Chaetomium， Staphylotrichum, Podospora呈显著负相关关系。 F. moniliforme与细菌属Nitrospira, Lysobacter, Pirellula, Gaiella，真菌属Chaetomium, Staphylotrichum, Tetracladium, Nectria, Acremonium, Leptosphaeria, Mrakiella, Stachybotrys有显著负相关关系。两个病原真菌的数量变化也与理化因素相关，两种病原真菌丰度都与土壤含水量呈显著负相关，另外，F. moniliforme丰度还与pH和C:N显著负相关。综上所述，秸秆覆盖会增加玉米茎腐病（根腐病）爆发的风险，病原菌数量的变化与某些土壤理化变量和微生物属密切相关。