摘要
引言 作物轮作是缓解烟草连作不利影响的重要农艺措施，但前茬禾本科作物对植烟土壤微生物群落及潜在功能的影响尚未得到系统验证。方法 基于为期三年的连续田间试验，本研究以烤烟–休耕体系（CK）为对照，建立烤烟–大麦轮作体系（DM）。综合采用土壤化学性质和酶活性测定、细菌16S rRNA和真菌ITS扩增子测序、可培养细菌分离以及温室盆栽再接种试验，评估大麦轮作后土壤环境和微生物群落的变化，并验证候选富集分离株的植物促生潜力。结果 与CK相比，DM显著（P < 0.05）提高了土壤溶解性有机碳、有效磷、速效钾和水解性氮，分别提高19.65%、3.23%、5.45%和5.90%；蔗糖酶、β-葡萄糖苷酶、酸性磷酸酶和N-乙酰-β-D-氨基葡萄糖苷酶活性分别提高23.80%、66.28%、15.23%和176.32%。扩增子测序表明，大麦轮作显著改变了土壤细菌和真菌群落。Sphingomonas和Burkholderia-Caballeronia-Paraburkholderia在DM下相对富集，并与多个土壤养分和酶活性变量显著相关；因此，将其定义为候选富集细菌类群。随后从DM土壤中获得属于这些类群的6株可培养分离株。在体外，这些分离株表现出不同的功能表型组合，包括在无氮培养基上生长、磷转化、解钾、解锌、铁载体产生和有机底物降解。温室盆栽试验表明，混合接种显著促进了烤烟生长，并提高了植株氮、磷和钾积累。结论 大麦轮作伴随着土壤有效养分、酶活性和微生物群落组成的显著变化，而从轮作富集类群中获得的可培养分离株在受控条件下表现出植物促生潜力。这些发现支持轮作富集微生物参与后续植物–土壤养分反馈的可能性，但其在田间轮作效应中的直接介导作用仍需进一步验证。本研究为理解大麦–烟草轮作的微生物生态效应和筛选潜在植物促生细菌提供了理论依据和候选微生物资源。
Introduction Crop rotation is an important agronomic practice for alleviating the adverse effects of continuous tobacco cropping, yet the effects of preceding gramineous crops on the microbial communities and potential functions of tobacco-growing soils have not been systematically verified. Methods Based on a three-year continuous field experiment, this study used a flue-cured tobacco–fallow system (CK) as the control and established a flue-cured tobacco–barley rotation system (DM). Soil chemical properties and enzyme activities, bacterial 16S rRNA and fungal ITS amplicon sequencing, culturable bacterial isolation, and greenhouse pot reinoculation experiments were integrated to evaluate changes in the soil environment and microbial communities following barley rotation and to verify the plant growth-promoting potential of candidate enriched isolates. Results Compared with CK, DM significantly ( P < 0.05) increased soil dissolved organic carbon, available phosphorus, available potassium, and hydrolyzable nitrogen by 19.65%, 3.23%, 5.45%, and 5.90%, respectively; sucrase, β-glucosidase, acid phosphatase, and N-acetyl-β-D-glucosaminidase activities increased by 23.80%, 66.28%, 15.23%, and 176.32%, respectively. Amplicon sequencing showed that barley rotation significantly altered soil bacterial and fungal community. Sphingomonas and Burkholderia-Caballeronia-Paraburkholderia were relatively enriched under DM and were significantly associated with multiple soil nutrient and enzyme activity variables; therefore, they were defined as candidate enriched bacterial taxa. Six culturable isolates belonging to these taxa were subsequently obtained from DM soil. In vitro , these isolates exhibited different combinations of functional phenotypes, including growth on nitrogen-free medium, phosphorus transformation, potassium solubilization, zinc solubilization, siderophore production, and organic-substrate degradation. Greenhouse pot experiments showed that mixed inoculation significantly promoted flue-cured tobacco growth and increased plant nitrogen, phosphorus, and potassium accumulation. Conclusion Barley rotation was accompanied by significant changes in soil available nutrients, enzyme activities, and microbial community composition, whereas culturable isolates obtained from rotation-enriched taxa showed plant growth-promoting potential under controlled conditions. These findings support the possibility that rotation-enriched microorganisms participate in subsequent plant–soil nutrient feedbacks, although their direct mediating role in field rotation effects requires further verification. This study provides a theoretical basis and candidate microbial resources for understanding the microbial ecological effects of barley–tobacco rotation and screening potential plant growth-promoting bacteria.