日光温室连作黄瓜根际微生物区系的变化

[目的]研究黄瓜再植病害的发生机理。[方法]选择种植年限分别为13、、5、7和8年的日光温室,采集0~20 cm根区耕层土壤,测定微生物类群和数量。[结果]连续种植5年的土壤中微生物数量最多,达2.2×108cfu/g（干土）;8年的最少,为2.7×107cfu/g（干土）。细菌占微生物总量的97%以上。随连作年限的增加,细菌和放线菌数量表现出先增加后减少的趋势,第5年达到最大值,分别为2.17×108和1.92×106cfu/g（干土）;真菌数量随连作年限的增加呈增长趋势。随连作年限的增加,氨化细菌、固氮菌和纤维素分解菌数量呈现先增加后降低的趋势,分别在连作5、3和3年达到最大值,而硝化细菌数量随连作年限的增加急剧下降。[结论]黄瓜连作显著地改变了根际微生物区系。     

脱硫渣施用量对盐碱地油葵根际微生物区系的影响

分析盐碱地油葵在不同脱硫渣处理下其根际与非根际细菌、真菌、放线菌以及氨化细菌、好气性纤维素分解菌、固氮菌、硝化细菌生理类群的区系动态变化,研究盐碱地油葵对不同脱硫渣处理的响应规律。结果表明,随着脱硫渣施用量的增加,土壤中细菌和放线菌及4类生理细菌类群的数量均呈现出先上升后下降的趋势,其中脱硫渣为1.5 t/hm2时,每克干土中细菌数量为1.81×106个,放线菌的数量为3.62×105个,氨化细菌为9.37×105个,好气性纤维素分解菌为95.01×104个,固氮菌为15.71×103个。真菌呈现出先快速下降后缓慢上升的趋势;适宜的脱硫渣施用量有利于油葵根际细菌、放线菌及4类细菌生理类群数量的提高,过高则微生物数量下降;施用脱硫渣前后,各微生物类群都表现出明显的根际效应。     

Iron Nutrition of Peanut Enhanced by Mixed Cropping with Maize: Possible Role of Root Morphology and Rhizosphere Microflora

Abstract

Field observations have indicated that Fe deficiency chlorosis symptoms in peanut are more severe and widespread in monoculture than intercropped with maize in calcareous soils of northern China. Here we report a pot experiment that investigated the mechanisms underlying the marked improvement in Fe nutrition of peanut grown in mixture with maize. Iron deficiency chlorosis occurred in the young leaves of peanut in monoculture and was particularly obvious at the flowering stage, while the young leaves of peanut grown in mixture with maize remained green throughout the experiment. The chlorophyll and HCl‐extractable Fe concentrations in young leaves of peanut grown in mixture were much higher than those in monoculture, indicating that maize may have markedly improved the peanut Fe nutrition. Growth in mixture was associated with greatly altered root morphology and microbial populations in the rhizosphere of peanut. Visual observation of peanut roots in monoculture showed that they were larger in diameter and shorter than those in mixture. Moreover, peanut roots in mixture with maize produced more lateral roots and had increased root length compared with plants in monoculture. Peanut grown together with maize showed obvious rhizodermal transfer cells in the subapical root zone, but cells with cell wall ingrowths were poorly developed in peanut in monoculture. Mixed culture resulted in a significantly decreased abundance of bacteria in the rhizosphere of peanut compared with monoculture, and electron microscope observations indicated that this was associated with a thicker mucigel layer on the root surface of peanut in mixture with maize. Several root morphological and rhizosphere microbial factors may thus have contributed to the improvement in Fe nutrition of peanut in mixed culture.     

微生物有机肥结合土壤改良剂防治烟草青枯病

盆栽试验设置了五个处理:对照(T1)、施用普通有机肥(T2)、施用SQY-7号微生物有机肥(T3)、石灰处理土壤后施用SQY-7号微生物有机肥(T4)、石灰和碳铵处理土壤后施用SQY-7号微生物有机肥(T5),用DGGE和平板计数法研究了根际土壤微生物群落的多样性,旨在探讨微生物有机肥及微生物有机肥结合土壤改良剂对烟草青枯病的防治效果和对烟草根际土壤细菌群落多样性的影响.结果表明:连作土壤中,施用普通有机肥(T2)不仅不能防治烟草青枯病,还提高了烟草青枯病的病情指数,而施用微生物有机肥处理(T3、T4和T5)对烟草青枯病的防治效果达66.7％～87.9％;施用微生物有机肥可显著改变根际微生物区系结构:T2处理的根际土壤细菌和放线菌数量较T1处理略有增加,真菌数量则较T1处理增加了1.1倍;T3和T4处理的根际土壤细菌分别较T1处理增加了3.5倍和6.1倍,同时,放线菌数量分别增加了3.7倍和3.5倍,而真菌数量分别下降了66.2％和70.1％;T5处理的根际土壤细菌和放线菌数量较T1处理分别增加了13.6倍和5.1倍,真菌数量下降了75.0％;各处理的细菌群落多样性均较T1处理增加.初步研究表明,连作病害土壤用石灰和碳铵预处理后再施用SQY-7号微生物有机肥能有效防控烟草青枯病和减缓连作生物障碍,其作用机制主要通过改变微生物区系和降低病原菌数量实现.     

Effects of dietary supplementation with benzoic acid (VevoVitall®) on the zootechnical performance, the gastrointestinal microflora and the ileal digestibility of the young pig

The addition of organic acids to diet of young pigs has been shown to improve their zootechnical performance. The aim of these experiments was to evaluate the effects of dietary supplementation with BA (VevoVitall®) on the zootechnical performance (DWG and FCR), the gastrointestinal microflora of the weaner piglet and to determine the effects on the ileal digestibility. For the zootechnical and microbiological evaluations 124 28-day-old piglets were used. During 32 days half of them were fed a maize–soybean meal based diet and the other half this diet supplemented with 0.5% BA. At the end of the study the stomach and caecum contents were sampled from 12 animals of each group for microbiological determinations. For the ileal digestibility study 60-day-old ileo-rectal anastomosed piglets were used and fed alternatively the same diet supplemented or not with 0.5% BA. Digestibilities of total nitrogen (N), energy (E) and amino acids (AA) were evaluated.

The BA group had significantly higher DWG and FCR than that of the control group. BA reduced almost all the determined bacterial populations of the gastrointestinal tract of the piglet. The reductions were significant for gastric lactic acid bacteria and caecal E. coli. The ileal digestibility of E and AA was numerically improved and that of N significantly increased in the BA group.     

Transporting and Exercising Unconditioned Horses: Effects on Microflora Populations

The objective of this study was to determine if transportation and exercise stress in horses affect the microflora populations in the equine hindgut. Four horses were subjected to three transport periods (0, 3, and 6 hours) with a 7-d rest period between each transport. Horses were fed 0.91 kg/day of Purina Impact All Stages 12% and had ad libitum access to Cynodon dactylon (Coastal Bermudagrass) hay. Fecal samples were collected before (0 hours) and after (48 hours) transport. In addition, three horses underwent a different standardized exercise test with a 7-d rest period between each exercise. Standardized exercise test intensity was determined by heart rate to validate if the horse was in aerobic or anaerobic work. The protocol for fecal sample collection after exercise was the same as for transport. Prokaryotic community profiling was conducted by 16S metagenomic analysis. After DNA evaluation, differences were found in the microbiome at transport 0 hours and grouped transport 3 hours time 48 and transport 6 hours time 48 (PERMANOVA P = .037) where Bacteroidetes increased 48 hours after transport and Firmicutes decreased 48 hours after transport. Exercise microbial communities showed no difference in either alpha or beta diversity when compared with controls (0 hours). In the present study, difference in microflora may have resulted from stress duration of transport rather than stress duration of exercise.     

红壤荒坡种草的微生物区系与作物生产潜力的初步研究

本研究对长江中下游红壤荒坡种植牧草后的微生物区系与红壤养分含量,以及种草初年的产量进行了比较分析。试验表明,荒坡种草2年后,微生物总数明显增加,好气性氨化细菌与硝化细菌开始发展,土壤养分含量有了增加;多年生禾本科牧草在秋播苗齐苗足与良好管理下,草量逐年增加;并讨论了进一步发展荒坡种草、提高生物产量的途径,对发展南方红壤旱地种草养畜提供了初步的实践依据。     

土默川平原不同玉米品种青贮饲料的品质比较

为筛选出适宜土默川平原用作青贮饲料的玉米品种,以内蒙古土默特左旗5个产量较高的玉米品种为原料,比较其青贮前后营养成分、发酵品质和菌群的变化,并运用灰色关联度分析法进行综合评价。结果表明,5个玉米品种青贮后营养保存较好,品质均有所改善。品种金岭367、京科968和先玉027青贮后的相对饲用价值较高(RFV>140),品种京科968、先玉027和金岭367的干物质含量和水溶性碳水化合物含量较高,是调制青贮饲料的优质原料。青贮后,各品种的粗蛋白含量下降(降幅3.46%~14.4%),但品种间无显著差异;品种京科968、先玉027和金岭367的中性洗涤剂纤维(NDF)和酸性洗涤纤维(ADF)含量较低,饲用价值较高。灰色关联度分析表明,金岭367玉米青贮后综合表现最优。     

沈阳市城市表土中微生物区系变化的初步研究

在沈阳市远郊-近郊-市区等不同城市化水平区内选取林地、草地和路边土几种不同利用方式下的表层土壤,对土壤中的微生物状况进行了初步分析。结果表明,随着城市化水平的提高,土壤中微生物的数量表现为明显的减少趋势。其中变化较大的是细菌,而真菌和放线菌的变化不明显。     

Effects of pentachlorophenol and 2,4,5-trichlorophenoxyacetic acid on the microflora of the soil in a beech wood

Summary Every second month for 2 years a beech forest floor was treated with pentachlorophenol and 2,4,5-trichorophenoxyacetic acid each in two concentrations. The microbial biomass and its respiration activity in the three litter horizons were measured during this time and during a recovery period of 2 years after the treatment was stopped. The microbial biomass, mainly fungi, was decreased dose-responsively, as was the respiration rate. The doubling time of the fungal biomass was estimated to be about 50–100 days in the F horizon, and considering the natural decreases and recovery times observed, it is suggested, following Domsch et al. (1983), that a biomass decrease of 75%–93.75% is tolerable, a decrease of less than 75% is negligible, and a decrease of over 93.75% is critical.