连栽木麻黄根际微生物群落结构和功能特征

以不同栽培代数的木麻黄(第1代FCP、第2代SCP、第3代TCP)根际土壤为试验材料,运用BIOLOG微平板和磷脂脂肪酸(PLFA)技术分析根际土壤微生物群落结构和功能多样性对多代连栽响应。结果表明,不同代数的土壤微生物对各类碳源的利用程度存在显著差异,连栽后木麻黄根际土壤微生物对碳源利用率显著下降。在6类碳源中,除胺类外,其他5种碳源均呈现FCP>SCP>TCP。PLFA分析共检测到11种PLFA生物标记,FCP土壤微生物PLFA生物标记总量明显高于SCP和TCP,3个代数土壤中含量最高的PLFA生物标记是i16:0、a15:0和18:1ω9c。土壤中特征微生物含量差异明显,细菌分布量最大,其次是真菌和放线菌。随栽植代数增加,细菌含量减少,真菌含量增加。土壤微生物群落多样性指数均呈现FCP>TCP>SCP,与土壤理化性质变化密切相关。可见木麻黄连栽显著影响其根际土壤微生物群落结构与功能,因此根际土壤微生态失衡可能是导致木麻黄连栽障碍的重要因素。     

Source of mycorrhizal inoculum influences growth of Faidherbia albida seedlings

Poor land use management and practice inhibit the growth and establishment of tree seedlings in dryland areas.We assessed arbuscular mycorrhizal fungi(AM)status of Faidherbia albida(Del.)A.Chev.trees grown on different land uses.We quantified the growth and nutrient uptake of F.albida seedlings inoculated with AM from different sources.These efforts were based on soil and fine root samples from the rhizosphere soils of F.albida trees.AM root colonization was determined using the gridline intersect method.Spores were extracted by the wet sieving and decanting method and identified to genus level.The seedling experiment had a completely randomized onefactorial design with four treatments and five replications.Faidherbida albida seedlings were grown in a greenhouse.All in situ F.albida trees were colonized by AM fungi.AM root colonization of F.albida trees was significantly higher(P<0.0086)in area exclosures than on lands used for grazing or cultivation.Spore abundance was significantly higher(P<0.0014)in area exclosures followed by cultivated land and grazing land.Glomus was the dominant genus in all land-uses.AM-inoculated F.albida seedlings grew better(P<0.05)than non-inoculated controls.Seedlings inoculated with AM from area exclosure had significantly(P<0.05)higher growth and nutrient uptake than those inoculated with AM from grazing and cultivated land.This emphasizes the importance of the native soil AM potential for better establishment of seedlings to achieve optimum plant growth improvement and assist in rehabilitation of degraded arid lands.     

高寒地区燕麦根际联合固氮菌研究 Ι固氮菌分离及鉴定

结合气相色谱仪,利用乙炔还原等方法对高寒地区重要饲用植物——燕麦(Avenasativa)根际联合固氮菌进行了分离和鉴定。结果表明,该地区燕麦根际联合固氮菌株较少(8株),菌株分布以根系表面(RP)最多,根表土壤(RS)次之,距根系较远的土壤(NRS)和根内(HP)最少,即:RP>RS>NRS≥HP;菌株固氮酶活性相差较大(C2H4112.5～1147.9nmol/mL·h),具有较高固氮酶活性的菌株较少(C2H4大于500nmol/mL·h只有2株);菌株均为革兰氏阴性菌,经鉴定分属Azotobacter(3株)、Pseudomonas(3株)和Azospirillus(2株)3个属。相对于其它生境和植物,高寒地区燕麦根际联合固氮菌种类较为单一。     

芽孢杆菌绿色荧光蛋白标记及其在小麦体表定殖的初探

 将来自质粒pAD4412的启动子和绿色荧光蛋白基因gfpmut3a插入大肠杆菌-枯草芽孢杆菌穿梭载体pBE2,构建成芽孢杆菌表达载体pGF P4412,用其转化野生型生防芽孢杆菌83-6和A-47等8个菌株,均得到良好的发光表型。质粒稳定性实验表明重组质粒pG FP4412稳定性为92%。借助荧光显微镜对gfp标记的菌株A-47-gfp在小麦体表的定殖进行初步的研究。结果表明:A-47-gfp能够在小麦根际及小麦体表定殖(包括根表和茎叶表面);相对于在茎叶表面定殖的A-47-gf p在根表定殖的菌体与根的结合更为牢固;从根基到根尖A-47-gfp的定殖量有明显的减少趋势。     

Endophytic-Host Selectivity of Discula umbrinella on Quercus alba and Quercus rubra Characterized by Infection, Pathogenicity and Mycelial Compatibility

The fungal endophytic–host relationships of Discula umbrinella and two oak species, Quercus alba and Quercus rubra, were characterized on the basis of endophytic infection, pathogenicity, and mycelial compatibility. Isolates of D. umbrinella were cultured from leaves of Q. alba and Q. rubra collected from a hardwood forest located in Patuxent Wildlife Research Center in Laurel, Maryland, USA. Endophytic infection was observed on sterile leaf discs and living 2-month-old seedlings of Q. alba and Q. rubra. Fungal-host reciprocal inoculations revealed the presence of conidiomata on both hosts but conidiomata production was more abundant on Q. alba. Isolates from Q. rubra produced milder disease symptoms on both oak species. Mycelial compatibility studies identified seven different MCG groups. MCG groups 1–3 contained isolates from both oak species whereas MCG groups 4–7 contained host specific isolates. Field studies monitored the seasonal appearance of the sexual fruiting structures, perithecia, as a possible source of new genetic variation that might alter host specificity/pathogenicity of the D. umbrinella isolates on Q. alba and Q. rubra hosts. Only 1–2% of the leaves contained perithecia throughout the sampling period (April–September). Isolates collected from Q. alba differed from those collected from Q. rubra in endophytic infection, pathogenic response, and perithecia production. The results of this study suggest that the endophyte–host relationship is one of host selective preference for Q. alba, but that the endophyte has the ability to maintain the endophytic/pathogenic life cycle on the less preferred host species, Q. rubra.     

不同供磷水平对柱花草和黑籽雀稗根际生理活性的影响

以热带柱花草和黑籽雀稗为材料，通过盆栽试验，研究不同磷水平对其根际酸性磷酸酶、微生物数量及根系活力的影响。结果表明：2种牧草根际酸性磷酸酶(ACP)活性随着磷浓度的增加而降低，在低磷(P0)处理时达最高，柱花草的ACP活性为603.24 mg/(kg·h)，黑籽雀稗为367.21 mg/(kg·h)。当高磷浓度处理时，柱花草根际ACP活性较黑籽雀稗低。各处理中，柱花草的根际微生物总量较黑籽雀稗高，柱花草根际真菌的数量随磷浓度的增加而减少，处理间差异达极显著水平，低磷处理时土壤真菌数量较多，这有利于根瘤菌的形成。2种牧草的根系活力随着施磷浓度的增加而递减。黑籽雀稗根系活力P0处理极显著高于P3和P4处理,显著高于P2处理。黑籽雀稗根系活力受供磷水平的影响大于柱花草。     

早期营养干预对幼龄反刍动物瘤胃微生物区系发育的影响

正常稳定的瘤胃微生物区系是反刍动物瘤胃健康的重要指标,且在瘤胃结构形态发育、微生物定植模式、免疫功能调节及抵御外源致病因子侵袭等方面发挥着重要积极作用。最近研究表明,新生反刍动物瘤胃微生物组成相对单一,但随着早期瘤胃发育过程中不同微生物群落相继开始定植并占据不同的生态位,此时的营养干预可能会形成特定的微生物群落组合并产生持久影响,这为进一步提高反刍动物生产性能和健康水平提供了更好的长期策略。本研究主要从3个方面详细综述了早期营养干预对瘤胃微生态系统发育的最新研究成果,包括探索幼龄反刍动物瘤胃形态及功能发育、寻找影响早期瘤胃微生物群落定植的因素及最佳调控“窗口期”的选择,并对宿主与微生物群落间的免疫互作进行简要剖析,以期为通过早期营养干预调控瘤胃微生物区系,提高反刍动物生产性能来应对全球畜牧业挑战,并为提高秸秆纤维利用率及抑制甲烷排放提供理论依据。     

膜下滴灌与沟灌海岛棉田土壤微生物特性的比较

对不同灌溉方式下土壤微生物特性的对比研究结果表明：膜下滴灌方式下棉田的微生物数量及根际、根外微生物数量均多于细流沟灌；两种灌溉方式都具有明显的根际效应；膜下滴灌使土壤处于厌气条件，土壤酶活性没有明显增加，但由于膜下滴灌可随水滴肥，适时适量供给棉花生长所需肥水，仍能满足海岛棉生长需求。     

2株重组根瘤菌在4个大豆品种根圈中定殖动态的比较研究

在灭菌和未灭菌土盆栽缩影条件下，比较研究了重组大豆根瘤菌HN01DL和TA113QD在4个不同品种大豆根圈中的定殖动态与水平，并初步考察了其与共生效应的关系。结果表明：HN01DL在渝豆1号和宁镇1号大豆根圈表现出较强的适应性和竞争性，而TA113QD则在Williams大豆根圈的适应性较强，在宁镇1号大豆根圈的适应性较差，且供试菌在4种大豆根圈定殖动态与水平的差异在共生效应上也有一定程度的反映，但未达到显著水平。     

Root Exudates of Rice Cultivars Affect Rhizospheric Phosphorus Dynamics in Soils with Different Phosphorus Statuses

Exudation of organic acids by the roots of three rice cultivars grown in three soils of different phosphorus (P) statuses, and their impacts on the rhizospheric P dynamics and P uptake by the rice plants, were investigated. Quantum root exudates from all the rice cultivars were significantly greater at 21 days after transplantation than at panicle initiation or flowering stages. Malic acid was the most predominant organic acid present in the rice root exudates (10.3 to 89.5 μmol plant^?1 d^?1), followed by tartaric, citric, and acetic acids. Greater exudation of organic acids from rice grown in P-deficient soil by all the rice cultivars suggested response of rice plant to P stress. Results indicate that the release of organic acids in the root exudates of rice plants can extract P from strongly adsorbed soil P fraction, thereby increasing native soil P utilization efficiency and ensuring adequate P nutrition for the growing rice plants.