球孢白僵菌在玉米根际的定殖及对根际微生物的影响

通过分生孢子诱变法获得了球孢白僵菌抗多菌灵突变株,测定球孢白僵菌不同抗性突变株对多菌灵的抗性水平及遗传稳定性.选择其中对多菌灵EC50为245.0697,抗性水平指数达到229.29的抗性突变株BC-8菌株作为定殖菌株.采用盆栽接种试验和涂抹平皿法测数等方法研究球孢白僵菌抗性突变株BC-8菌株在玉米根际的定殖能力及对根际微生物数量的影响.结果表明:BC-8菌株可以在玉米外根际和根表定殖,但未在根内分离到;玉米移栽后28 d,外根际、根表的分离数量达到最大值;用BC-8菌株分生孢子悬浮液处理玉米幼苗后,玉米根际细菌、真菌及放线菌的数量均比对照减少;玉米移栽后14d,根际细菌、真菌、放线菌的数量与对照相比都有大幅度的减少;移栽后28 d,根际各种微生物的数量都有所增加,但与对照相比,仍呈减少趋势;移栽后42 d,根际微生物的数量趋于稳定.     

拮抗菌XB16在香蕉体内的定殖及对抗病相关酶活性的影响

XB16(Bacillus subtilis)是分离自香蕉根部组织的芽孢杆菌,该菌株对香蕉枯萎病有显著的拮抗作用。为进一步研究XB16在香蕉体内的定殖情况及对抗病相关酶活性的影响,通过浓度梯度诱导法,获得在含有300μg/mL利福平的NA培养基上稳定生长且对病原菌拮抗能力保持不变的XB16突变株。在温室条件下采用3种不同的接种方法,研究XB16在香蕉体内的定殖动态。结果表明,采用伤根淋菌液法和灌根法接种,XB16均能在香蕉体内定殖和传导,显示出该菌株在香蕉体内有较好的定殖能力。两种接种方法中,定殖菌数量在香蕉各组织中的消长动态均表现为先增长后缓慢下降;但是采用喷雾法接种XB16后在香蕉各组织中没有检测到标记菌,说明该接种方法不能使XB16在香蕉体内定殖。灌根法接种XB16后取香蕉假茎组织测定了香蕉体内抗病相关酶的活性。结果表明,拮抗菌株处理后过氧化物酶(POD)和多酚氧化酶(PPO)均比接种病原菌和清水对照明显提高,PPO和POD酶活最高峰分别出现在接种后第5天和第7天。两种酶在接种后的第15天仍保持较高活性,推测诱导抗性是XB16菌株的防病机制之一。     

大豆根际土壤镰孢菌不同分离方法比较

镰孢菌(Fgsarium)引起的大豆根腐病是难防治的土传病害之一.土壤中镰孢菌多样性水平很高,并对其中致病菌种群动态及寄主抗性表现有一定影响.镰孢菌分离在其多样性研究中起重要作用,报道的镰孢菌分离方法很多,但分离效果有一定差异.本文对影响分离效果的相关内容进行了研究,比较了稀释平板法和土粒平板法.结果表明,当抗生素浓度增加到常量的4倍时可很好抑制细菌,并对真菌数目没有显著影响;不同抗生素组合对镰孢菌分离有一定影响;无菌水和水琼脂处理不同样品量与菌落数(CFU)之间均呈线性关系(R2>0.9),随着样品量的增加菌落数呈递增趋势;无菌水处理中镰孢菌的分离比率为21.0%,略高于水琼脂处理的10.0%;供试2种培养基对镰孢菌分离比率没有显著影响,与孔雀绿琼脂培养基(MGA)相比,蛋白胨.五氯硝基苯琼脂培养基(PPA)对镰孢菌的分离比率较高为20.93%.培养方法对镰孢菌分离比率影响较大,土粒平板法分离比率均大于60.0%,远高于稀释平板法(分离比率均低于6%).     

黑土区不同轮作系统大豆根际镰孢菌种群结构和数量

对中国科学院海伦农业生态试验站长期定位区大豆连作17年、小麦-玉米-大豆轮作、玉米-大豆迎茬和大豆连作2年,分别取分枝期、花期和鼓粒期的大豆根际土壤,采用土粒平板法进行镰孢菌分离,探讨大豆连作对镰孢菌种群结构和数量的影响.根据形态学特征鉴定出6种镰孢菌,即锐顶镰孢(F.acuminatum Ellis ＆ Everhart)、黄色镰孢(F.culmorum(W.G.Smith)Saee.)、木贼镰孢(F.equiseti(CoMa)Saec.)、禾谷镰孢(F. graminearum Schwabe)、尖孢镰孢(F. oxysporum Schleeht.)和腐皮镰孢(F. solani(Mart.)Sacc.).在不同生育期及不同轮作系统大豆根际土壤中尖孢镰孢(F. oxysporum)数量较高,与其它种类相比差异显著(P＜0.05),是大豆根际土壤中的优势菌.不同轮作系统大豆根际土壤以尖孢镰孢数量平均值最高,其次为腐皮镰孢;不同轮作系统镰孢菌总量动态变化一致,花期轮作镰孢菌数量最高为1.54 x 104个·-1干土,与大豆连作17年相比差异明显.在3个生育期大豆连作17年尖孢镰孢数量均略低于轮作.     

植物根际促生菌及其在克服连作障碍中的潜力

连作障碍是中国现代农业发展的一个突出问题,植物根际促生菌(plant growth-promoting rhizobacteria,PGPR)的深入研究和发展为解决这一难题展现了诱人的前景.PGPR作为最具防病潜力与应用价值的一类生防菌,不仅能促进植物生长,增加作物的产量,还能提高防病能力.本文介绍PGPR的相关定义、优良菌株筛选及商业化产品等背景,分析PGPR的作用机制,包括直接促生作用和间接生防作用,并探讨其在解决植物连作障碍上的潜力,旨在为PGPR菌剂的推广及应用提供参考.     

大豆根际促生菌Sneb207对不同种类线虫毒性的研究

从大豆根瘤中分离到1株根际促生菌Sneb207,经鉴定为巨大芽孢杆菌(Bacillus megaterium).室内测定结果表明:其发酵产物对豆苗生长促生效果显著,发酵液灭菌后仍具有促生活性,具有广泛的应用价值.用该菌发酵液测定了对各种线虫的作用,结果表明毒力作用具有差异,大小顺序分别为大豆胞囊线虫、北方根结线虫、水稻干尖线虫和腐烂茎线虫.不同浓度发酵液对大豆胞囊线虫均有较好的防治作用,与无菌水对照处理有显著差异.说明细菌菌株Sneb207是控制大豆胞囊线虫病且促进大豆生长的有效因子.     

不同接种和处理方式对巨桉幼苗青枯病发生的影响

桉树青枯病的发生由于影响因素较多导致其人工接种重复性差,因此需要获得稳定的青枯病感染,同时在此基础上可以进行桉树苗期青枯病的防治研究。在本研究中采用水培后伤新根和袋苗未经水培直接伤根后转移到青枯菌液中浸泡6、12、18、24 h后移植,调查桉树幼苗青枯病发病率和生长状况,同时通过在接种前喷施不同浓度的BR、Me JA、SA 3种激素,诱导桉树抵抗青枯菌侵染,调查处理后苗木死亡率。结果表明,未经过水培直接伤根移植的苗木更容易感染青枯菌,经过24 h菌液浸泡处理后的幼苗的死亡率,达到86.67%,同时发现SA对缓解桉树青枯病的发病有明显的作用,且在喷施浓度为0.001 mmol时使用,青枯菌侵染的植株仍有75.0%的存活率。本研究获得了桉树幼苗稳定感染青枯病的一种方式,为室内研究桉树幼苗感染青枯病的机制奠定基础,同时获得了降低桉树青枯病发生的处理方式,为桉树苗期青枯病的防治提供一种方案。     

pBBR1MCS2-Tac-EGFP广宿主载体适宜标记Ralstonia so-lanacearum

利用标记基因追踪病原菌在植物体内的入侵和定殖,是研究病原菌-寄主互作的重要手段.本研究利用电转化法将广宿主载体pBBR1MCS2-Tac-EGFP导入青枯雷尔氏菌(Ralstonia solanacearum)GMI1000菌株中,获得了青枯雷尔氏菌带绿色荧光标记的转化子.转接试验结果表明,转化子的抗生素抗性和绿色荧光...     

花生青枯菌粗毒素最适产生条件及其对热、紫外线的敏感性

对花生青枯菌菌株在不同的温度、pH值、培养时间、菌液浓度等条件下产毒素的情况,以及毒素对热、紫外线的敏感性进行了研究。结果表明:培养温度为25～28℃、pH值为7、培养时间为3d是花生青枯菌粗毒素最适的产生条件、菌液浓度对花生青枯菌产毒素的影响不大;花生青枯菌粗毒素对热效应比较敏感,100℃水浴1h时,其生物活性降低89.8%,几乎完全丧失其生物活性。对紫外线则不敏感,在25W紫外光下照射30min、60min、90min、120min均不影响其生物活性。     

基于玉米-大豆轮作的不同施肥体系对大豆开花后根系形态及产量的影响

探讨玉米-大豆轮作条件下,降低生产成本、减少环境污染的大豆施肥模式,是目前东北大豆生产需要解决的技术问题。本研究基于建立的玉米-大豆轮作体系设置了5种施肥处理,分别为：T1：玉米施用化肥,大豆不施肥;T2：玉米施用化肥,大豆施用有机肥;T3：玉米施用化肥,大豆施用1/2量的化肥;T4：玉米施用化肥,大豆施用化肥;T5：玉米与大豆所需化肥总量一次性全部施入到玉米种植年份,大豆不施肥。分析了不同施肥模式对大豆不同生育期0~10、10~20、20~30cm土层深度内大豆根系干物质积累、根系形态特征时空变化以及与产量的关系。结果表明,经两个轮作周期,T2处理大豆产量最高为 2959kg·hm-2,比T4处理显著高出7.3%,产量提高主要体现在大豆的株高、主茎节数、单株荚数和单株粒数等性状的改善,而T1、T3、T5处理的大豆产量比T4处理显著低出15.4%,8.5%和5.0%。T2处理显著增加了大豆R6期0~10cm土层的根重密度,比T4处理显著高出42.3%,且与产量呈显著正相关,相关系数为0.655(p < 0.01);T2处理也明显增加了大豆R1期0~10、10~20cm土层以及R6期20~30cm土层的根长密度,分别比T4处理显著高出25.3%、71.3%和27.6%,且与产量呈显著正相关,相关系数为0.692 (p < 0.01)。与T4处理相比,尽管T3处理显著增加了大豆R1期10~20、20~30cm土层的根重密度和R6期10~20cm土层的根长密度及根表面积密度,但均与产量呈显著负相关。T4处理只显著增加R1期单位体积的根表面积,而对大豆根平均直径和其它时期单位体积的根表面积的影响不大。因此,不同施肥措施影响大豆根系特征及其产量的关系问题比较复杂。施用有机肥可通过增加表土层根的重量以及深土层根的长度从而提高大豆的产量。因此在有机肥源供应充足的地区,玉米、大豆两区轮作基础上,玉米收获后秋施15t·hm-2有机肥,是提高大豆产量,降低生产成本,减轻化肥应用负面环境影响的替代措施。     

烟草青枯病菌巢式PCR检测方法的建立及应用

利用细菌16S-23S r DNA内源转录间隔区通用引物L1/L2扩增烟草青枯病菌基因组DNA,并对其扩增产物进行克隆测序,经与近缘种序列多重比对分析后,设计1对特异性引物Rs F/Rs R,用于包括烟草青枯病菌在内的15种不同细菌、5种真菌、3种卵菌基因组DNA的PCR扩增。结果表明:在优化的反应体系与程序条件下,该对引物只能从烟草青枯病菌中扩增出241 bp的特异片段,并通过序列测定验证了其准确性;将引物Rs F/Rs R与细菌通用引物L1/L2进行巢式PCR扩增后,其检测灵敏度在DNA水平上可达0.4 fg/μL,较常规PCR提高1 000倍,表明该对引物能有效地用于烟草组织及土壤中青枯病菌的检测。此结果对烟草青枯病的早期诊断、快速检测及病害流行学研究具有重要意义。     

基于间套作弱光胁迫下作物源库协调与产量研究进展

光能在作物进行光合作用和籽粒产量形成中起着重要作用。随着我国种植结构和区划的调整,间套作种植模式在一些适宜地区得到广泛应用,增加了农田生产力。然而,间套作种植方式下,由于受高位作物荫蔽影响,低位作物在某一生长阶段常常处于弱光胁迫环境中。弱光胁迫不仅会引起作物生长发育不良,而且会制约作物产量潜力的提升。本文以间套作荫蔽环境下的大豆源库关系为例,综述了弱光胁迫调节作物源库器官生长发育的国内外研究现状;阐述了源库协调与作物产量之间的关系以及现有间套作作物产量研究概况与存在的不足;探讨了未来间套作种植下作物在源库关系与产量研究的发展方向。     

Productivity and water use of alfalfa and subsequent crops in the semiarid Loess Plateau with different stand ages of alfalfa and crop sequences

Alfalfa (Medicago sativa L.) plays an important role in crop–livestock mixed farming on marginal land in the semiarid Loess Plateau. However, the duration, yield performance and water use of long-term alfalfa stands and choice of appropriate subsequent crops are not clear. A 5-year field experiment was conducted at Zhonglianchuan, Gansu Province, China from 2001 to 2005. Productivity and water use were determined and compared between (1) three alfalfa stands that were 1–5 (A1–5), 6–10 (A6–10) and 11–15 (A11–15) years old during the trial; (2) alfalfa using conventional cultivation and a water-harvesting technique (RA1–5); and (3) conventional crop rotation (CK) and four 5-year crop sequence rotations sown after 10-year-old alfalfa had been ploughed, being millet–wheat–potato–pea–potato (MWLPL); millet–corn–corn–wheat–wheat (MCCWW); millet–potato–wheat–corn–corn (MLWCC) and millet–fallow–pea–potato–pea (MFPLP). Forage yield peaked in 7-year-old alfalfa (5740 kg ha⁻¹), but 9-year-old alfalfa had the maximum forage yield profit (4477 kg ha⁻¹ y⁻¹) in terms of whole growing years. Soil water use efficiency (WUE_S in terms of forage yield and soil water use) of alfalfa increased dramatically up to the 11th year, and then leveled off from year 12 to 15. Forage yield and WUE_B/ET (WUE in terms of aboveground biomass and evapotranspiration) of alfalfa were significantly higher using water harvesting compared with conventional cultivation, but were significantly lower than CK. Soil water content did not change in CK as stand age increased, but it decreased in conventional alfalfa stands. After 10 years of alfalfa, a fallow year was not necessary before planting annual crops as soil water was greatly restored after sowing subsequent annual crops. Yield of some crops in the four crop sequence rotations did not differ significantly from CK. MWLPL and MLWCC had more aboveground biomass than MCCWW and MFPLP but the choice of crop sequence needs to be further considered.     

Impact of different crop rotations and tillage systems on weed infestation and productivity of bread wheat

Crop rotation and tillage systems have important implications for weed infestation and crop productivity. In this study, five tillage systems viz. zero tillage (ZT), conventional tillage (CT), deep tillage (DT), bed sowing (60/30 cm with four rows; BS₁) and bed sowing (90/45 cm with six rows; BS₂) were evaluated in five different crop rotations viz. fallow-wheat (FW), rice-wheat (RW), cotton-wheat (CW), mungbean-wheat (MW) and sorghum-wheat (SW) for their effect on weed infestation and productivity of bread wheat. Interaction between different tillage practices and cropping systems had significant effect on density and dry biomass of total, broadleaved and grass weeds, agronomic and yield-related traits, and grain yield of bread wheat. The un-disturbed soils (ZT) under fallow-wheat or mungbean-wheat rotations favoured the weed prevalence (a total weed dry biomass of 72.4–109.6 and 105.6–112.1 g m⁻² in first and second year, respectively). Contrary to this, the disturbed soils (CT, DT, BS₁ and BS₂) had less weed infestation with either of the rotations (a total weed biomass of 0.4–7.1 and 1.1–5.4 g m⁻² in first and second year, respectively). Sorghum-wheat rotation had strong suppressive effect on weed infestation in all tillage systems. The impact of crop rotation was more visible during second year of experimentation. Bed sown wheat (BS₁ and BS₂) in mungbean-wheat rotation had the highest wheat grain yield (6.30–6.47 t ha⁻¹) compared to other tillage systems in different crop rotation combinations.     

Population dynamics of Verticillium species in cauliflower fields: Influence of crop rotation,debris removal and ryegrass incorporation

Verticillium wilt, caused by the soil-borne fungus Verticillium longisporum, leads to economic losses in cauliflower production in Belgium. Development of sustainable control measures of the disease is necessary. Previous studies in our laboratory have shown that incorporation of ryegrass can reduce the viability of V. longisporum microsclerotia in soil. However, field experiments are lacking in Belgian conditions. To gain knowledge about the population dynamics of V. longisporum and its relationship with Verticillium wilt, experiments were conducted from 2006 to 2010 in two cauliflower fields (Oppuurs and Ardooie) with history of Verticillium wilt. Three main crop systems (fallow, cauliflower and cauliflower followed by removal of debris) and two cover crop systems (no cover crop and ryegrass) were tested. The results of this study showed that (i) crop rotation intensity of cauliflower cultivation does not affect the inoculum density of microsclerotia forming Verticillium species in soil, (ii) amendment of lignin-rich ryegrass may reduce the soil inoculum, and (iii) seasonal fluctuations of inoculum densities occur but any soil inoculum variation above a level of one microsclerotium per gram of soil does not affect disease levels. Furthermore, we found that Verticillium wilt of cauliflower in Ardooie was reduced in soil containing Verticillium tricorpus-like organisms. The Verticillium isolate Vt305 obtained from the cauliflower field in Ardooie was morphologically similar to V. tricorpus, but its rDNA ITS region showed 100% identity with the non-pathogenic species Verticillium isaacii, recently described in literature.     

油料作物油脂合成调控研究进展

植物油脂不仅是人类可食用油的主要来源,也是人类生产生活中重要的可再生原料.本文概述了植物油脂的生物合成途径,从母体效应、QTL、GWAS等多个方面总结了油料作物油脂合成的遗传学研究进展,同时探讨了已知的油脂合成调控相关基因的功能.本文综述了该领域的研究现状,为深入了解油料作物油脂合成调控网络提供了参考,也为油料作物的分...