Colonization by Klebsiella variicola FH-1 stimulates soybean growth and alleviates the stress of Sclerotinia sclerotiorum

Sclerotinia stem rot,caused by Sclerotinia sclerotiorum,is a destructive soil-borne disease leading to huge yield loss.We previously reported that Klebsiella variicola FH-1 could degrade atrazine herbicides,and the vegetative growth of atrazine-sensitive crops(i.e.,soybean)was significantly increased in the FH-1-treated soil.Interestingly,we found that FH-1 could promote soybean growth and induce resistance to S.sclerotiorum.In our study,strain FH-1 could grow in a nitrogen-free environment,dissolve inorganic phosphorus and potassium,and produce indoleacetic acid and a siderophore.The results of pot experiments showed that K.variicola FH-1 promoted soybean plant development,substantially improving plant height,fresh weight,and root length,and induced resistance against S.sclerotiorum infection in soybean leaves.The area under the disease progression curve(AUDPC)for treatment with strain FH-1 was significantly lower than the control and was reduced by up to 42.2%within 48 h(P<0.001).Moreover,strain FH-1 rcovered the activities of catalase,superoxide dismutase,peroxidase,phenylalanine ammonia lyase,and polyphenol oxidase,which are involved in plant protection,and reduced malondialdehyde accumulation in the leaves.The mechanism of induction of resistance appeared to be primarily resulted from the enhancement of transcript levels of PR10,PR12,AOS,CHS,and PDF1.2 genes.The colonization of FH-1 on soybean root,determined using CLSM and SEM,revealed that FH-1 colonized soybean root surfaces,root hairs,and exodermis to form biofilms.In summary,K.variicola FH-1 exhibited the biological control potential by inducing resistance in soybean against S.sclerotiorum infection,providing new suggestions for green prevention and control.

Different genotypes regulate the microbial community structure in the soybean rhizosphere

The soybean rhizosphere has a specific microbial community,but the differences in microbial community structure between different soybean genotypes have not been explained.The present study analyzed the structure of the rhizosphere microbial community in three soybean genotypes.Differences in rhizosphere microbial communities between different soybean genotypes were verified using diversity testing and community composition,and each genotype had a specific rhizosphere microbial community composition.Co-occurrence network analysis found that different genotype plant hosts had different rhizosphere microbial networks.The relationship between rhizobia and rhizosphere microorganisms in the network also exhibited significant differences between different genotype plant hosts.The ecological function prediction found that different genotypes of soybean recruited the specific rhizosphere microbial community.These results demonstrated that soybean genotype regulated rhizosphere microbial community structure differences.The study provides a reference and theoretical support for developing soybean microbial inoculum in the future.

Biofilm Development, Plant Growth Promoting Traits and Rhizosphere Colonization by <i>Pseudomonas entomophila</i>FAP1: A Promising PGPR

Among the diverse soil bacteria, plant growth promoting rhizobacteria (PGPR) mark an important role in enhancing plant growth through a range of beneficial functions. This is mainly achieved by effective rhizosphere colonization by PGPR. Biofilm development by PGPR is considered as a survival strategy over the planktonic mode of growth under stress and natural conditions. Since the performance of microbial inoculants under field conditions is not always consistent due to various biotic and abiotic factors affecting survival, colonization and functions. Therefore, the rhizobacteria with efficient colonization ability and exhibiting multiple PGP traits are expected to perform better. We hypothesized that the biofilm forming ability of PGPR on plant root will be an added advantage to rhizosphere colonization. Therefore, we have selected a promising isolate of PGPR through random screening programme from rhizoplane of wheat (Triticum aestivum). The selection was based on biofilm development ability, multifarious PGP activities (production of indole acetic acid, sidero-phore, phosphate solubilization, hydrogen cyanide, ammonia production and biocontrol activity) and tolerance to salinity and heavy metals. The selected isolate was identified by 16 s rRNA partial gene sequencing as Pseudomonas entomophila-FAP1. The strain FAP1 formed strong biofilm in microtitre plate, glass surface as well as on the roots of wheat seedlings. Biofilm forming capacity of the FAP1 was characterized by scanning electron microscopy and confocal laser scanning microscopy. FAP1 exhibited biofilm-related traits such as the production of exopolysaccharides, EPS (1501.33 ± 1.08 μg ml-1), alginate (212.81 ± 1.09 μg ml-1), swarming motility (22 ± 1.36 mm), swimming motility (31 ± 2.12 mm) and cell surface hydrophobicity (63%). Rhizosphere colonization by FAP1 was found 7.5 Log CFU g-1 of soil comparable with rhizoplane colonization (7.2 Log CFU g-1 of root). Therefore, biofilm formation on plant roots by promising PGPR may be included as an additional criterion to select a better rhizosphere colonizer. Further, study with mutant deficient in biofilm should be developed for comparative study to explore the exact contribution of biofilm in root colonization under natural soil-plant system.

Foliar Dicamba Application Has No Lasting Effects on Microbial Activities in the Soybean Rhizosphere

The proliferation of glyphosate-resistant weeds has resulted in significant losses in the productivity of crops such as corn, soybean, and cotton. As a result, new crop varieties with resistance genes from other herbicides, such as 2,4-D and dicamba, have been developed as part of alternative weed control cropping systems. However, little is known about how the application of these herbicides impacts the microorganisms that carry out nutrient cycling in the soil of these cropping systems, particularly in the rhizosphere, the soil compartment immediately adjacent to the root system which is pivotal to plant nutrient uptake. The purpose of the current study was to assess the effects of dicamba on soil enzyme activities linked to C, N, and P cycling in the rhizosphere of resistant soybean plants. While dicamba had no significant effects on the activities of enzymes linked to C or P cycling in the rhizosphere, N-acetylglucosaminidase activity was temporarily inhibited, but recovered by three days after application. These results suggest there are no long-lasting negative effects of dicamba in the rhizosphere of treated plants when applied at field rates.

Colonization of Rice Roots by a Green Fluorescent Protein-Tagged Isolate of Ustilaginoidea virens

The fungus U. virens is the causal agent of rice false smut disease. The green fluorescent protein (GFP) was used to mark this fungus in order to visualize and analyze the colonization and infection processes in vivo. Using epifluorescence microscopy colonization and infection on rice roots were visualized in vivo. After inoculation for 2 to 15 d, it was observed that the conidia and their germ-tubes had penetrated into epidermis of young roots. The hyphae were found inside the root xylem 18 d after inoculation. Generally, the transformed fungus colonized the rhizosphere, the cortex as well as the vascular tissues with symptoms of root necrosis observed. The results of this work show that U. virens colonize not only rice panicles but also the roots.

Soybean(Glycine max)rhizosphere organic phosphorus recycling relies on acid phosphatase activity and specific phosphorusmineralizing-related bacteria in phosphate deficient acidic soils

Bacteria play critical roles in regulating soil phosphorus(P) cycling. The effects of interactions between crops and soil P-availability on bacterial communities and the feedback regulation of soil P cycling by the bacterial community modifications are poorly understood. Here, six soybean(Glycine max) genotypes with differences in P efficiency were cultivated in acidic soils with long-term sufficient or deficient P-fertilizer treatments. The acid phosphatase(AcP) activities, organic-P concentrations and associated bacterial community compositions were determined in bulk and rhizosphere soils. The results showed that both soybean plant P content and the soil AcP activity were negatively correlated with soil organic-P concentration in P-deficient acidic soils. Soil P-availability affected the ɑ-diversity of bacteria in both bulk and rhizosphere soils. However, soybean had a stronger effect on the bacterial community composition, as reflected by the similar biomarker bacteria in the rhizosphere soils in both P-treatments. The relative abundance of biomarker bacteria Proteobacteria was strongly correlated with soil organic-P concentration and AcP activity in low-P treatments. Further high-throughput sequencing of the phoC gene revealed an obvious shift in Proteobacteria groups between bulk soils and rhizosphere soils, which was emphasized by the higher relative abundances of Cupriavidus and Klebsiella, and lower relative abundance of Xanthomonas in rhizosphere soils. Among them, Cupriavidus was the dominant phoC bacterial genus, and it was negatively correlated with the soil organic-P concentration. These findings suggest that soybean growth relies on organic-P mineralization in P-deficient acidic soils, which might be partially achieved by recruiting specific phoCharboring bacteria, such as Cupriavidus.

Application of organic manure as a potential strategy to alleviate the limitation of microbial resources in soybean rhizospheric and bulk soils

The development and vigor of soil microorganisms in terrestrial ecosystems are frequently constrained by the limited availability of essential elements such as carbon(C),nitrogen(N),and phosphorus(P).In this study,we investigated the impact of long-term application of varying levels of organic manure,low(7.5 Mg ha^(−1)yr^(−1)),moderate(15.0 Mg ha^(−1)yr^(−1)),and high(22.5 Mg ha^(−1)yr^(−1)),on the stoichiometry of enzymes and the structures of the microbial communities in soybean rhizospheric and bulk soils.The main goal of this research was to examine how soil microbial resource limitations in the rhizosphere respond to different long-term fertilization strategies.The soil enzymatic activities were quantified,and the structure of the microbial community was assessed by analyzing phospholipid fatty acid profiles.When compared to the bulk soil,the rhizospheric soil had significant increases in microbial biomass carbon(MBC),nitrogen(MBN),and phosphorus(MBP),with MBC increasing by 54.19 to 72.86%,MBN by 47.30 to 48.17%,and MBP by 17.37 to 208.47%.Compared with the unfertilized control(CK),the total microbial biomasses of the rhizospheric(increased by 22.80 to 90.82%)and bulk soils(increased by 10.57 to 60.54%)both exhibited increases with the application of organic manure,and the rhizospheric biomass was higher than that of bulk soil.Compared with bulk soil,the activities of C-,N-and P-acquiring enzymes of rhizospheric soil increased by 22.49,14.88,and 29.45%under high levels of organic manure,respectively.Analyses of vector length,vector angle,and scatter plots revealed that both rhizospheric and bulk soils exhibited limitations in terms of both carbon(C)and phosphorus(P)availability.The results of partial least-squares path modelling indicated that the rhizospheric soil exhibited a more pronounced response to the rate of manure application than the bulk soil.The varying reactions of rhizospheric and bulk soils to the extended application of organic manure underscore the crucial function of the rhizosphere in mitigating limitations related to microbial resources,particularly in the context of different organic manure application rates.

Rhizosphere soil bacterial community composition in soybean genotypes and feedback to soil P availability

Soil with low phosphorus (P) availability and organic matter contents exists in large area of southwest of China, but some soybean genotypes still show well adaptations to this low yield farmland. However, to date, the underlying mechanisms of how soybean regulates soil P availability still remains unclear, like microbe-induced changes. The objective of the present study was to compare the differences of rhizosphere bacterial community composition between E311 and E109 in P-sufficiency (10.2 mg kg^-1) and P-insufficiency (5.5 mg kg^-1), respectively, which then feedback to soil P availability. In P-sufficiency, significant differences of the bacterial community composition were observed, with fast-growth bacterial phylum Proteobacteria, genus Dechloromonas, Pseudomonas, Massilia, and Propionibacterium that showed greater relative abundances in E311 compared to E109, while in P-insufficiency were not. A similar result was obtained that E311 and E109 were clustered together in P-insufficiency rather than in P-sufficiency by using principal component analysis and hierarchical clustering analysis. The quadratic relationships between bacterial diversity and soil P availability in rhizosphere were analyzed, confirming that bacterial diversity enhanced the soil P availability. Moreover, the high abundance of Pseudomonas and Massilia in the rhizosphere of E311 might increased the P availability. In the present study, the soybean E311 showed capability of shaping rhizosphere bacterial diversity, and subsequently, increasing soil P availability. This study provided a strategy for rhizosphere management through soybean genotype selection and breeding to increase P use efficiency, or upgrade middle or low yield farmland.

Effects of phosphorus on nutrient uptake and rhizosphere acidification of soybean (G/ycine max L.)

Pot experiment was conducted to examine how application of KH2PO4 （0-165 mg·kg^-1 P） to affect nutrient ion uptake and rhizosphere acidification of soybean （Glycine max L.） grown in greenhouse for 90 days. When supplied of 82 and 165 mg·kg^-1 P, soybeans showed excessive poison. Under all kinds of P levels, the K, Ca, Na and Mg concents in plant tissues were as below order K was nodules 〉 roots 〉 pods 〉 shoots; Ca was shoots 〉 roots 〉 nodules 〉 pods; Na was roots 〉 nodules 〉 pods 〉 shoots and Mg was shoots 〉 nodules 〉 roots 〉 pods. K concent in plant tisssues had greater effect on rhizosphere acidification than other cations in this experiment irrespective of P supply, and was significantly negative to pH. Na concentration was significantly positive to pH. Excessive P supply induced rhizosphere acidification, pH decreased as P supply increased from 82 to 165 mg·kg^-1. Ash alkalinity in shoots and roots was significantly positively correlated with rhizosphere pH irrespective of P supply. All these results suggested that P supply affected nutrient uptake, induced ash alkalinity to increase and rhizosphere pH to decrease in soybean.

根内根孢囊霉对连作大豆苗期植株生长发育的影响

以非转基因型大豆品种黑农48(病害敏感型的高蛋白品种)作为试验材料,以根内根孢囊霉(Rhizophagus intraradices,R.intraradices)为试验菌剂分别接种于大豆连作1年和非连作的大田土壤中,采用碱解离-酸性品红染色法和形态观测法测定根内根孢囊霉对连作苗期大豆根系丛枝菌根(Arbuscular mycorrhizal,AM)真菌侵染率、植株株高及茎粗的影响。结果显示,未施加根内根孢囊霉菌剂的大豆,连作导致AM真菌侵染率增高,株高和茎粗降低。而接种根内根孢囊霉的大豆,AM真菌侵染率、株高和茎粗均显著提高,表明根内根孢囊霉对连作大豆苗期植株生长发育具有一定促进作用。本研究为AM真菌的田间应用及提升黑龙江绿色大豆生产地位提供了理论依据。

大豆连作根际土壤微生物群落构建特征

研究连作对大豆根际土壤中细菌、真菌群落组成、构建的影响,为大豆连作障碍的生物防治和农田土壤修复提供理论支持。试验于2021-2022年在沈阳农业大学铁西区定位试验站进行,试验站土壤类型为棕壤土。以玉米-大豆轮作(对照)和大豆连作根际土壤为研究对象,利用16SrDNA、ITS高通量测序技术,结合土壤化学性质和土壤酶活性测定,分析连作对大豆土壤化学性质、酶活性以及根际微生物多样性、群落构建特征的影响。结果表明:连作下,土壤全氮、全磷、全钾等土壤化学性质指标含量下降,速效钾、pH值升高;连作显著提高土壤蔗糖酶和过氧化氢酶活性,显著降低土壤脲酶、亮氨酸氨肽酶活性和N-乙酰氨基葡萄糖苷酶活性。土壤细菌多样性指数连作处理(4.63)低于轮作处理(5.34),细菌属水平下,连作增加鞘氨醇杆菌属(Sphingobacterium)和卡氏伯克霍尔德菌属(Burkholderia,LRR:1.4%;LCR:2.4%)相对丰度;土壤真菌多样性指数连作处理低于轮作处理,真菌属水平下,连作增加病原真菌镰刀菌属(Fusarium,LCR:20.5%;LRR:13.2%)相对丰度。在群落组装过程中,大豆连作根际土壤细菌群落构建主要由确定性过程主导;玉米大豆轮作根际土壤细菌群落构建主要由随机过程主导;大豆连作根际土壤真菌群落构建和玉米大豆轮作根际土壤真菌群落构建由随机过程主导。连作引起大豆根际土壤环境因子、细菌、真菌群落组成及构建的变化,病原菌相对丰度增加,其中镰刀菌(Fusarium)相对丰度的增加可能是导致大豆连作障碍发生的重要因素。

番茄疫霉根腐病菌拮抗细菌HP8-1的鉴定及生物防治潜力

【目的】探究HP8-1在番茄上的生物防治潜力,为番茄疫霉根腐病的生物防治提供优良生物防治资源。【方法】通过形态学观察、生理生化特性检测并结合16S rRNA序列分析鉴定HP8-1菌株,探讨其对植物病原菌的抑菌效果和生物学功能及在番茄根际的定殖能力,并通过盆栽试验测定其对番茄疫霉根腐病的防治效果和对番茄生长的影响。【结果】HP8-1为多粘类芽孢杆菌(Paenibacillus polymyxa),对多种植物病原菌具有抑菌效果,具有解磷、分解蛋白、分解纤维素、产嗜铁素和产吲哚乙酸等生物学功能;HP8-1在番茄根系和根际土壤具有稳定的定殖能力,尤其是在接种疫霉菌的条件下其定殖量趋于增加并显著高于未接种疫霉菌的条件;HP8-1处理对番茄疫霉根腐病具有明显的防治效果,防治效果达到57.41%;同时,HP8-1处理显著促进番茄植株生长、提高叶绿素含量和根系活力。【结论】HP8-1菌株稳定定殖在番茄根系和根际土壤,防治番茄疫霉根腐病,促进番茄生长,是对番茄疫霉根腐病具有生物防治潜力的资源。

饼粕肥对芽胞杆菌在烟草根际定殖及促生作用的影响

为了探究饼粕肥对芽胞杆菌在烟草根际定殖的作用及定殖后芽胞杆菌对烟苗的促生效应,在烟苗种植土中分别添加解淀粉芽胞杆菌HZ13(P1)、饼粕肥(P2)、饼粕肥与HZ13即时混合物(P3)及饼粕肥与HZ13共发酵培养物(P4),以无添加的烟苗种植土为对照(CK)。提取各处理烟苗根际代谢物并分析组间差异代谢物,比较不同处理对HZ13-RFP的趋化作用、烟苗根际微生物数量及烟苗生长指标的影响。结果表明,P4根际代谢物种类最多,且有机酸数量最多;P4和CK的差异代谢物20种,以有机酸和糖类为主,含量最丰富的有葡萄糖和麦芽糖,和P1的差异代谢物26种,有机酸和糖类最多,含量最丰富的有麦芽糖、鹅去氧胆酸、琥珀酸、海藻糖、果糖和苏氨酸,和P3的差异代谢物23种,有机酸最多,含量最丰富的有琥珀酸、鹅去氧胆酸和苏氨酸。P4根际代谢物对HZ13-RFP的趋化性及促生作用最强。烟苗移栽后40 d,P4根际HZ13总菌数较P3高12.15倍,占根际细菌总数的12.12%,而P1为0。P4烟苗最大叶面积较P3、P1和CK分别提高30%、140%和160%,株高较P3、P1和CK分别提高100%、230%和300%。综上,饼粕肥与芽胞杆菌共发酵培养对芽胞杆菌在烟苗根际定殖及促生效果最好。

大豆根际微生物的研究进展

根际微生物组被称为植物的“第二基因组”,在植物生长、发育和健康等方面发挥了重要作用。微生物在大豆根系土壤营养元素循环过程中起着十分关键的作用,即大豆根际土壤微生物可直接或间接地影响大豆的生长健康、营养物质吸收及病害防治等,大豆的生长也对土壤微生物的群落结构产生重要影响。本文主要针对近些年来关于大豆根际土壤微生物多样性及结构变化情况进行概述,主要包括不同的大豆种质、耕作栽培方式、生长时期、根际分泌物以及外界处理等条件下大豆根际土壤微生物的群落结构变化,以及大豆根际微生物与土传病害的关系,同时对未来关于大豆根际微生物的相关研究等方面提出建议与展望。

细菌根际黏附的界面作用机制研究

界面作用是细菌在环境中黏附、定殖、形成生物膜和发挥生态功能的基础和前提,对植物吸收养分、病原微生物拮抗具有重要意义。微生物-植物根际相互作用研究大多数从生态学和分子生物学角度出发,应用多种组学手段研究根系分泌物对于根际微生物定殖数量、群落组成和生理功能的影响,忽略了细菌定殖过程中物理、化学的界面作用机制及其对黏附的贡献。本文从界面作用机制出发,探讨了不同类型根系分泌物对细菌表面性质、细菌胞外聚合物(EPS)分子组成以及黏附功能的调控作用;梳理了黏附过程中细菌-植物生物大分子相互作用的主要模式及其微观机制;归纳了根际定殖过程可视化研究方法和微生物-植物生物大分子相互作用的分析手段;提出了根际生物分子组成分析、黏附蛋白质功能预测、根际定殖原位观测方法等亟需加强的研究方向。

合成菌群对大豆根际和根内微生物群落的影响

为了探究施用合成菌群对大豆生长和根际及根内微生物的影响,利用大豆根际促生菌,通过功能互补和功效叠加原则构建4组合成菌群(SynComs)。根据盆栽试验的促生效果选出最优菌群并取其根际土和根系分别进行宏基因组测序和16S rRNA基因测序,探究合成菌群对大豆根际土壤和根内微生物群落和功能的影响。盆栽试验表明,合成菌群SynCom 4可显著增加大豆株高、地上鲜重、根长、根鲜重和根瘤数。SynCom 4由克雷伯氏菌JP07(Klebsiella JP07)、克雷伯氏菌GD04、假单胞菌LH19(Pseudomonas LH19)、不动杆菌JP32(Acinetobacter JP32)、克雷伯氏菌PKO08、芽孢杆菌JK32(Bacillus JK32)、寡养单胞菌GD03(Stenotrophomonas GD03)和克雷伯氏菌LH13组成。宏基因组测序结果表明,接种SynCom 4提高了细菌微酸菌纲(unclassified_Acidimicrobiia)、藤黄色单胞菌属(Luteimonas)、绿屈挠菌纲(unclassified_c_Chloroflexia)、热厌氧杆状菌目(unclassified_o_Thermoanaerobacteroles)等的相对丰度,增加了参与氮代谢、磷转化、吲哚乙酸和赤霉素生物合成等功能基因的相对丰度。16S rRNA基因测序结果表明,SynCom 4增加了大豆根内细菌群落多样性,提高了黄单胞菌科(unclassified_f_Xanthomonadaceace)、食氢产水菌属(Hydrogenophaga)、根瘤菌目(unclassified_o_Rhizobiales)、黄杆菌科(norank_f_Xanthobacteraceae)等的相对丰度。PICRUSt2功能预测表明,SynCom 4增强了与氨基酸、维生素、脂质和次级代谢产物合成有关的功能。综上,宏基因组测序和16S rRNA基因测序结果表明,SynCom 4显著改变了根际和根内微生物群落的结构和组成,提高了微生物的多样性,增加了菌属和功能基因的相对丰度。施用SynCom 4有效促进了大豆生长,改变了根际和根内的细菌微生物群落结构和功能。

大豆和玉米茬口对冬小麦根际土壤细菌群落结构和功能的影响

为探明黄淮海地区玉米茬口和大豆茬口微生物遗留效应的差异,于2023年在长达4 a(2019—2023年)的长期定位试验田中采集冬小麦拔节期的根际土壤样品,采用16S高通量测序技术并结合Tax4Fun2功能预测分析,研究玉米茬口(M)和大豆茬口(S)下冬小麦拔节期根际土壤细菌群落结构及功能对不施氮(N0)和常规施氮(N240,纯氮240 kg/hm2)共4个处理(MN0、SN0、MN240、SN240)的响应。结果表明,门水平下,变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)、拟杆菌门(Bacteroidetes)和放线菌门(Actinobacteriota)为冬小麦拔节期根际优势菌门,优势菌门相对丰度为66.66%~69.56%。N0施氮量S茬口的拟杆菌门相对丰度比M茬口显著增加了19.10%(P<0.05);N240施氮量S茬口的变形菌门相对丰度比M茬口显著增加了11.90%(P<0.05)。目水平下,Vicinamibacterales与伯克氏菌目(Burkholderiales)为优势菌目,优势菌目相对丰度为18.42%~19.68%。N0施氮量S茬口的Vicinamibacterales相对丰度比M茬口显著减少了13.69%(P<0.05),伯克氏菌目相对丰度显著增加了11.31%(P<0.05)。通过Tax4Fun2功能预测,与KEGG数据库对比发现,N0施氮量下新陈代谢分类中的7个二级功能途径相对丰度存在显著差异(P<0.05);进一步通过相关性分析发现,Vicinamibacterales和伯克氏菌目与氨基酸代谢途径存在极显著相关关系(P<0.01)。冬小麦土壤细菌有26个功能基因参与土壤氮循环途径,其中反硝化功能基因相对丰度最高。N0施氮量M茬口的norB、norC、nirS型反硝化功能基因相对丰度显著高于S茬口(P<0.05)。综上,不同施氮量下茬口均造成冬小麦拔节期根际土壤细菌群落结构发生变化,不同茬口通过改变根际土壤细菌群落结构进一步影响细菌群落氮代谢功能。

根内根孢囊霉对正茬和迎茬大豆生物量的影响

本研究旨在探究根内根孢囊霉(Rhizophagus intraradices)在缓解大豆迎茬障碍和提高大豆生物量方面的效应。以‘黑农48’品种的大豆为对象,通过湿筛倾析-蔗糖离心法、碱解离-酸性品红染色法以及直接测量法,分别对AM真菌孢子密度、侵染率及大豆生物量进行了测定。结果显示,正茬大豆田的根际土壤中孢子密度是迎茬的2.2倍。在自然土壤条件下,接种R.intraradices的正茬与迎茬土壤中的大豆植株,其根系AM真菌侵染率和生物量均显著高于未接种处理组,其中根长最为显著,分别提高了31.60%和33.57%。在迎茬土壤中接种R.intraradices菌剂的大豆生物量与正茬土壤中未接种处理组的接近。在相同接菌处理条件下,灭菌土壤中的大豆植株根系AM真菌侵染率和生物量均低于自然土壤。本研究这些发现为缓解大豆迎茬障碍和提升大豆产量提供了重要的理论依据。

Arbuscular Mycorrhizal Fungal Community Structure in Soybean Roots: Comparison between Kanagawa and Hokkaido, Japan

The objectives of this study were to determine arbuscular mycorrhizal fungi (AMF) community structure in colonized roots of soybean cultivated from Kanagawa and Hokkaido in Japan and to relate the community structure to environmental conditions, which included soil type, preceding crops, and soil chemical properties. The average number of AMF OTU (operational taxonomic unit) colonizing soybean roots collected from Kanagawa and Hokkaido was 11.2 and 5.8, respectively, a significant difference. Moreover, AMF from the family Gigasporasera was not identified in soybean roots collected from Hokkaido, suggesting that AMF in the family Gigasporasea is absent or rare in the soybean fields of sampled in Hokkaido. We postulate that the soil type, preceding crops or soil chemical properties are not the underlying factor differentiating AMF community structure colonizing in soybean roots between Kanagawa and Hokkaido. Instead we conclude that temperature and phosphate absorption coefficient are the determining factors of AMF OTU in this study.

大豆低聚肽对嗜酸乳杆菌的增殖效果研究

[目的]探究大豆低聚肽对嗜酸乳杆菌生长的影响,为乳酸菌体内定植提供思路。[方法]试验组加入不同质量浓度的大豆低聚肽于MRS肉汤培养基中,培养嗜酸乳杆菌48 h测定OD_(600 nm);测定不同培养时间下嗜酸乳杆菌培养液的OD_(600 nm),绘制生长曲线;以300、600、1200 mg/kg剂量的大豆低聚肽-嗜酸乳杆菌菌悬液连续灌胃抗生素诱导的肠道菌群紊乱小鼠7 d,测定大豆低聚肽作用下小鼠体质量变化。[结果]40、30、20 mg/mL大豆低聚肽能明显增加嗜酸乳杆菌菌液浊度,促进嗜酸乳杆菌增殖;能使嗜酸乳杆菌培养12 h后进入对数生长期,提前进入快速增长状态并提高增长速度;低剂量组(300 mg/kg)、中剂量组(600 mg/kg)、高剂量组(1200 mg/kg)均能促进小鼠体质量增长,且600 mg/kg中剂量组体质量增加2.89 g,与阴性对照组差异显著。[结论]大豆低聚肽在体外能明显促进嗜酸乳杆菌增殖,添加的大豆低聚肽质量浓度为40 mg/mL时增殖效果最为显著。能促进小鼠体质量增长,但其促进乳酸菌的体内定植机制需要进一步评价。