暗紫贝母茎腐病微生物群落结构差异及土壤驱动因素分析

Microbial community disparities and soil determinants in stem rot pathogenesis of Fritillaria unibracteata

摘要:

背景 暗紫贝母是珍稀中药“川贝母”的主要植物来源。茎腐病导致暗紫贝母叶片枯黄，茎腐烂，植株死亡，产量显著降低。茎腐病的发生往往与茎部病原菌感染、土壤根际微生物失衡及土壤环境因子变化相关联，但暗紫贝母茎腐病的发生机制目前尚不清楚。目的 通过分析茎腐病暗紫贝母根际土壤和茎部微生物与健康植株的群落结构差异，为揭示暗紫贝母茎腐病发病原因和病害控制奠定理论基础。方法 采用Illumina MiSeq技术对暗紫贝母健康根际土壤(SFH)、患病根际土(SFR)和无植物土壤(SFW)，以及患病贝母茎(LFD)和健康贝母茎(LFH)中的细菌和真菌群落结构和多样性进行测序和分析。同时测量了不同健康状况贝母根际土壤理化性质。结果 茎腐病组土壤的pH、有机质(soil organic matter, SOM)、有效磷(available phosphorus, AP)、速效钾(available potassium, AK)、全氮(total nitrogen, TN)、全钾(total potassium, TK)和硝态氮(nitrate nitrogen, NO₃^--N)水平显著高于健康组和对照组(P<0.05)。贝母根际土壤样品的Chao1、Observed_species、Pielou_e、Shannon指数显著高于茎部样品(P<0.05)。茎腐病植株组的α多样性指数显著低于健康植株组。链核盘菌属(Monilinia)在患病植株和患病土壤中的相对丰度均显著高于健康植株和健康土壤组(P<0.05)。链核盘菌属(Monilinia)所属的柔膜菌目(Helotiales)在患病贝母茎部组(LFD)中为具有显著差异的生物标志物。速效钾(AK)对根际土壤细菌和真菌群落结构的影响最为显著，链核盘菌属(Monilinia)与全氮呈显著正相关。患病植株茎部组(LFD)中由链核盘菌属(Monilinia)实现大部分氮代谢通路功能。结论 暗紫贝母茎腐病的发生导致根际土壤和茎中的微生物多样性下降。链核盘菌属对暗紫贝母茎腐病的发生起着重要作用。

Abstract:

Background Fritillaria unibracteata Hisao et K. C. Hsia serves as the primary botanical origin of the precious Chinese medicinal material Fritillariae Cirrhosae Bulbus. Stem rot in F. unibracteata manifests as leaf yellowing, stem decay, and plant mortality, causing a substantial reduction in yield. This disease is often linked to stem pathogen infections, imbalances in soil rhizosphere microorganisms, and alterations in soil environmental factors. Nevertheless, the underlying mechanism of stem rot in F. unibracteata remains elusive.Objective We analyzed the disparities in the microbial community structures of rhizosphere soil and stem between diseased and healthy F. unibracteata plants, aiming to establish a theoretical basis for elucidating the causes of stem rot in F. unibracteata and formulating effective disease control strategies.Methods Illumina MiSeq was employed to sequence and analyze the community structure and diversity of bacteria and fungi in five types of samples: healthy rhizosphere soil (SFH), diseased rhizosphere soil (SFR), plant-free soil (SFW), diseased (LFD) and healthy (LFH) stems of F. unibracteata. Concurrently, the physicochemical properties of the rhizosphere soil of F. unibracteata under different health conditions were measured.Results The levels of soil pH, organic matter, available phosphorus, available potassium, total nitrogen, total potassium, and nitrate nitrogen in the stem rot group were higher than those in the healthy group and the control group (P<0.05). The alpha-diversity indices (Chao1, Observed_species, Pielou_e, and Shannon) of the rhizosphere soil samples were higher than those of the stem samples (P<0.05). The alpha-diversity indices in the LFD group were lower than those in the LFH group. The relative abundance of Monilinia in LFD and SFR groups were higher than those in LFH and SFH groups (P<0.05). Helotiales was a significantly different biomarker in the LFD group. The effect of available potassium on the bacterial and fungal community structures in the rhizosphere soil was most significant. The relative abundance of Monilinia was positively correlated with total nitrogen (P<0.05). Most of the nitrogen metabolism pathway functions in the LFD group were carried out by Monilinia.Conclusion Stem rot in F. unibracteata results in a decline in microbial diversity of both the rhizosphere soil and stems. Monilinia was a crucial factor in the development of stem rot in F. unibracteata.