影响引入微生物根部定殖的因素

从外界引入的各类有益微生物如生防菌（ＢＣＡ）和根际促生菌或增产菌（ＰＧＰＲ,ＹＩＢ）到种子表面随其生根发芽而蔓延或直接到根表沿根分布定殖。外来微生物在根际定殖的过程为与根尖接触,沿根分布,最后在根际建立自己的种群。定殖的位点以ＰＧＰＲ为例,是表皮细胞间隙,或侧根、根毛基部。外来微生物在根际定殖动态变化的原因,由于根际生物的和非生物的因素引起的。生物因子除去外来微生物本身的生理特性,还有根际土著微生     

稻株上拮抗细菌的定殖及其对土著细菌的影响

在温室条件下,通过分批播种、接种纹枯病菌Rhizoctonia solani,以及在水稻分孽盛期喷雾拮抗细菌Pseudomonas fluorescens Pf7-14 (天然的抗萘啶酮酸菌株) 和B5423-R(Bacillus subtilis B5423的利福平抗性突变体)的菌悬浮液,并通过定期取样,平板系列稀释法回收,测定了菌株Pf7-14、B5423-R和土著细菌群体在水稻健株和纹枯病株上的种群数量,所获结果如下:①当相同的浓度(约2.0×108cfu/ml)的菌悬浮液喷雾到叶片时,菌株Pf7-14定殖的时间比菌株B5423-R长,且在相同的时间内,菌株Pf7-14的平均群体数量高于菌株B5423-R;②在健康的水稻茎部,菌株Pf7-14的两个高、低不同浓度处理的平均群体数量均表现出随时间降低的趋势;相比,较低浓度(4.0×107cfu/ml)的B5423-R在茎部的平均群体数量随着时间的下降,而较高浓度(2.0×108cfu/ml)的B5423-R的平均群体数量在水稻乳熟至黄熟期保持稳定或略有增长;③当病斑面积占取样茎面积的比率为20%～35%时,在应用1和14d后菌株Pf7-14在健茎的平均群体数量分别是病茎的6倍多和2倍多,差异均达到显著性的水平(P=0.05),而菌株B5423-R 在应用1d后病茎的数量比在健茎显著性地低大约1倍,但在7～14d后,病茎的数量比在健茎显著性地高5～6倍,群体在病茎表现出相对的增长;④土著细菌群体在病斑茎部是健茎的6～7倍.这些结果表明两类拮抗细菌有着明显不同的定殖习性,在病斑上B5423比Pf7-14具有更强的竞争能力,是一类更好的生防制剂;同时表明引入的拮抗细菌同土著细菌群体在营养和空间上竞争激烈,且土著细菌群体更具有竞争优势.     

影响引人微生物根部定殖的因素

从外界引入的各类有益微生物如生防菌(BCA)和根际促生菌或增产菌(PGPR,YIB)到种子表面随其生根发芽而蔓延或直接到根表沿根分布定殖．外来微生物在根际定殖的过程为与根尖接触,沿根分布,最后在根际建立自己的种群．定殖的位点以PGPR为例,是表皮细胞间隙,或侧根、根毛基部．外来微生物在根际定殖动态变化的原因,由于根际生物的和非生物的因素引起的．生物因子除去外来微生物本身的生理特性,还有根际土著微生物与外来微生物的相互作用,更重要的是植物基因型对微生物定殖的影响．非生物因子包括土壤环境、土壤结构和含水量,土壤温度和土壤pH值均能影响外来微生物在根部的定殖．     

油茶内生拮抗细菌Y13的定殖能力及其对土著细菌的影响

采用抗利福平标记法,定期取样、平板稀释法回收等方法,检测拮抗菌株Y13在油茶叶片内的定殖能力;以平板培养及16S rDNA法分析菌株Y13对油茶叶片内土著细菌种群的影响,为油茶炭疽病的生态治理提供理论依据。结果表明,菌株Y13在油茶健株和病株叶内均能稳定定殖,接种30 d时仍分别能检测到6.60×103CFU/g和3.56×103 CFU/g的标记菌株;油茶叶片内可培养内生细菌主要属于5个属的7个已知种,分别为芽孢杆菌属(Bacillus)、赖氨酸芽孢杆菌属(Lysinibacillus)、克雷伯菌属(Klebsiella)、鞘氨醇菌属(Sphingomonas)和假单胞菌属(Pseudomonas),以芽孢杆菌属和赖氨酸芽孢杆菌属为优势属。菌株Y13对不同处理油茶叶片内的群落结构和数量有明显的影响,能促进土著细菌群体的多样性,同时能够显著提高油茶叶片内的枯草芽孢杆菌数量,有利于抑制油茶炭疽病病原菌的增长。     

L型氨基酸对烟草赤星病菌毒素毒性的影响

为确定不同氨基酸对烟草赤星病菌产生的毒素毒性的影响,作者采用摩擦接种处理法、浇根处理法、种子根处理法三种生物测定方法,确定了以烟草种子根处理法作为烟草赤星病菌的毒性测定方法。用12种氨基酸分别以5种不同浓度与AT毒素混合接种,根长测定结果表明：L-谷氨酰胺,L-天冬酰胺,L-组氨酸所有供试浓度均增强病原菌毒素的毒性,而其余9种L型氨基酸对烟草赤星病菌GL-6产生的毒素有抑制作用,其中L-甲硫氨酸、L-亮氨酸、L-赖氨酸适宜浓度可明显降低供试病原菌毒素对烟草的致病性,与对照差异极显著,其有效浓度分别为0．02mg／ml、0．02mg／ml、0．02～2mg／ml。     

内生细菌在荔枝体内的定殖及其防病保鲜功能

用含有GFP基因标记的内生细菌菌株BS-2-gfp和TB2-gfp,采用喷雾接种的方法,研究其在荔枝叶片、花、幼果及成熟果实果皮内的定殖动态及其与防病保鲜之间的关系.结果表明:内生细菌BS-2-gfp和TB2-gfp能在荔枝叶片、花、幼果及采后果皮上定殖,能在各组织内繁殖并可在花和幼果间传导.内生细菌在荔枝叶片上的定殖因季节和荔枝生长期的不同而异,与秋季相比,春季定殖期限长,定殖量大.内生细菌在荔枝不同部位的定殖时间和定殖量也不同,在叶片上接种37d后还可分离回收到接种的2种目标细菌,在花上接种10d后就回收不到BS-2-gfp,而成熟荔枝果皮上2种菌的定殖量最大.防病试验表明,当荔枝霜疫病的病情指数急剧上升时,TB2-gfp在荔枝果皮的定殖量达到最大,为1.90×106CFU.g-1FM;保鲜试验发现,TB2-gfp菌株的保鲜效果优于BS-2-gfp,菌株在荔枝果皮内的定殖量也高于菌株BS-2-gfp,表明供试内生细菌在荔枝果皮的定殖量与其防病及保鲜效果呈正相关.     

不同化合物对烟草赤星病菌毒素的钝化研究

为确定几种不同化合物对烟草赤星病菌产生的毒素毒性的影响,作者采用摩擦接种处理法、浇根处理法、种子根处理法3种生物测定方法,确定了以烟草种子根处理法作为烟草赤星病菌的毒性测定方法。用6种化合物分别以5种不同浓度与AT毒素混合接种,根长测定结果表明：氯化铁、硫酸亚铁、硫酸锰和柠檬酸在0．02—20mg/mL浓度范围内、钼酸钠在0．02—2mg/mL浓度范围内对对烟草赤星病菌毒素有明显钝化作用;所有处理中钼酸钠0．02mg/mL、柠檬酸0．02mg/mL浓度处理效果最好,其次为钼酸钠0．2mg／mL处理浓度。     

土壤有益细菌在植物根际竞争定殖的影响因素

在土壤有益微生物应用于生物肥料、生物杀虫剂、植物生长刺激剂和生物处理剂的过程中,根际定殖具有重要作用。细菌在植物根际定殖是一个比较复杂的过程,影响定殖能力的因素也是复杂多样的。本文综述了参与根部竞争定殖的生物因素,包括受细菌遗传控制的某些特性如鞭毛/运动性、趋化性、多糖、位点特异重组酶/菌落阶段变异、NADH脱氢酶,植物根的分泌物和植物种类等;影响微生物根际定殖的非生物因素如土壤类型、土壤特性和土壤温度等,探讨了影响微生物根际定殖的主要研究方向。     

硅酸盐细菌NBT菌株在小麦根际定殖的初步研究

对硅酸盐细菌NBT菌株进行了耐药性标记,得到稳定的链霉素抗性标记菌NBT菌株,采用选择性培养基分离计数,通过琼脂平板和盆栽试验,研究了标记菌NBT在小麦根际的定殖动态及影响因素。结果表明,在灭菌土盆栽中,播种后9d左右NBT菌株在小麦根际的定殖水平达最高(1．4×10^8cfu·g^-1根土),播种后54d左右趋向稳定,NBT菌株细胞数量为2．4×10^3cfu·g^-1根土;未灭菌土盆栽中,播种后9d左右NBT菌株的定殖水平达最高(3．8×10^8cfu·g^-1根土),60d左右趋向稳定,菌数为3．1×10^3cfu·g^-1根土,牛物和非牛物因素对NBT菌株定殖小麦根系有影响。     

植物内生细菌的分离、分类、定殖与应用

植物内生细菌已成为国内外的研究热点,目前已从植物中分离得到许多不同种属的植物内生细菌,其中有的具有促生与防治病害等对宿主植物有利的作用,而一些则具有潜在的致病性。研究人员利用多种方法对植物内生细菌的内生定殖行为进行研究,发现了有意义的定殖规律,例如,某种植物内生细菌对其宿主的侵染能力明显强于另一种内生细菌。目前,尽管植物内生细菌还有不少问题有待解决,但它在农业上的巨大应用潜力业已彰显。     

Inhibitory effect of Trichoderma isolates on growth of Alternaria alternata,the causal agent of leaf spot disease on sunflower,under laboratory conditions

Several species of the genus Alternaria are involved in leaf spot disease of sunflower, with Alternaria alternata being the dominant species responsible for this disease in Iran and many other sunflower-producing areas, worldwide. The disease causes a progressive destruction of the photosynthetic apparatus, resulting in annual yield loss. The routine disease management strategies are not effective for disease control; hence, alternative measures for disease management are of great interest. In the present study, the efficacy of Trichoderma harzianum T22 and Trichoderma sp. on biological control of the causal agent was evaluated under laboratory conditions. The effect of Trichoderma isolates on dry weight (DW) and radial growth (RG) rate of A. alternata was evaluated using dual culture, volatile and non-volatile cellular metabolites. The results obtained in this study revealed that in both Trichoderma isolates, non-volatile cellular metabolites had the highest inhibitory effect on DW and RG rate of the causal agent. Owing to explicit inhibitory effect of non-volatile cellular metabolites on A. alternata, the inhibitory effects of different concentrations of non-volatile cellular metabolites were evaluated on DW and RG rate of the A. alternata. The obtained results showed that non-autoclaved 75 and 50% concentrations and undiluted (100%) autoclaved non-volatile cellular metabolites from Trichoderma sp. had the highest inhibitory effect on DW and RG rate of the causal agent. The overall results of this study reveal that Trichoderma spp. have excellent efficacy on biological control of A. alternata under laboratory condition; such that, further studies on the potential of Trichoderma spp. in biological control of Alternaria leaf spot disease of sunflower under green house and field conditions are necessary.     

Integrated control of tobacco black shank by combined use of riboflavin and <Emphasis Type="Italic">Bacillus subtilis</Emphasis> strain Tpb55

We investigated the effect of riboflavin on the biocontrol activity of Bacillus subtilis Tpb55 against Phytophthora nicotianae (Pn), which causes tobacco black shank. Riboflavin (0.2 mg ml^?1) significantly improved the biocontrol activity of Tpb55 (2.0 × 10⁸ cfu ml^?1). Riboflavin (0.02–0.5 mg ml^?1) alone could not significantly inhibit Pn growth. However, it enhanced the B. subtilis population, both in vitro and in tobacco roots and significantly increased the activity of defense enzymes, peroxidase, catalase, superoxide dismutase, and β-1,3-glucanase, in the roots of B. subtilis-treated tobacco seedlings. Our results indicate that riboflavin can stimulate the growth of B. subtilis Tpb55 and induce resistance to Pn in tobacco plants. These findings should boost the prospects for practical application of B. subtilis Tpb55 as a biocontrol agent against black shank of tobacco.     

Biological control against bacterial wilt and colonization of mulberry by an endophytic Bacillus subtilis strain

Forty-five bacterial isolates were collected from surface-sterilized leaves of mulberry ( Morus alba L.). By screening their antagonistic activities against Ralstonia solanacearum in vitro , four isolates showed a remarkable inhibitory effect. The evaluation of the antagonistic strains against bacterial wilt of mulberry indicated that the strain Lu144 effectively reduced disease incidence. In the greenhouse, Lu144 displayed effective biological control against bacterial wilt of mulberry when it was applied to sterile or nonsterile soil before the infection by the pathogen. Based on bacteriological properties and 16S rRNA gene sequencing, Lu144 was identified as a strain of Bacillus subtilis . The endophytic population and infection process of Lu144 in mulberry seedlings was explored following recovery of the green fluorescent protein (GFP)-labeled Lu144 and examination of the labeled strain by confocal laser scanning microscopy. Interestingly, the infection of GFP-labeled Lu144 cells into the mulberry seedlings occurred through the cracks formed at the lateral root junctions and the zone of differentiation and elongation, and the cells were able to develop and transfer in mulberry and mainly in the intercellular spaces of different tissues. The population of the GFP-labeled Lu144 inoculant was larger and more stable in leaves than that in roots and stems.     

柠檬醛熏蒸对互隔交链孢生长及其产毒的抑制作用

互隔交链孢是一种重要的能产生交链孢酚（AOH）等真菌毒素的植物病原菌。精油是重要的抑制病原菌侵染的挥发性植物提取物,其活性组分包括柠檬醛等。本研究表明柠檬醛可高效地抑制互隔交链孢的生长和AOH毒素的产生。柠檬醛熏蒸能够引起互隔交链孢菌丝断裂影响其延伸,而对其分生孢子结构的影响不明显。柠檬醛能够引起互隔交链孢活性氧生成的紊乱,这可能是导致AOH显著下降的原因之一。由于柠檬醛能高效抑制互隔交链孢生长和产毒,因此其可作为传统熏蒸剂的潜在替代品,以防控互隔交链孢引起的病害以及毒素污染。柠檬醛抑制互隔交链孢生长产毒的研究为其开发与应用奠定了良好的基础。     

水葫芦黑斑病菌Alternaria alternata的生物学特性研究

在不同试验条件下培养水葫芦黑斑病菌Alternaria alternata菌株,探讨其主要的生物学特性,结果表明：该菌株生长的最佳培养基为PSA,最佳C源为葡萄糖,弱碱性和中性N源对该菌菌丝生长具有明显的促进作用,而酸性N源对其具有抑制作用。菌株生长的最佳pH值为pH7,最适温度为27℃。湿度越大,对菌株生长越有利。     

枯草芽孢杆菌菌剂对人参黑斑病的生物防治效果

为明确枯草芽孢杆菌可湿性粉剂(WP)对人参黑斑病的防治效果及对人参生长的安全性,采用生长速率法测定枯草芽孢杆菌对人参黑斑病菌的室内抑菌效果,采用田间小区试验评价枯草芽孢杆菌对人参黑斑病的防治效果及其对人参的安全性.室内抑菌试验结果表明:枯草芽孢杆菌对人参黑斑病菌的菌丝生长具有较好的抑制作用,EC50和EC90分别为0....     

Changes in the leaf proteome profile of Mentha arvensis in response to Alternaria alternata infection

Plant pathogenic fungi cause important yield losses in crops. A proteomic approach was used to study the changes in the leaf proteome profile of the plant Mentha arvensis infected with a necrotrophic fungus, Alternaria alternata. High-resolution two-dimensional gel electrophoresis (2-DE) followed by colloidal Coomassie staining and mass spectrometric analysis was used to identify highly abundant proteins differentially expressed in response to fungal infection. From a total of 210 reproducibly detected and analyzed spots, the intensity of sixty-seven spots was altered, and forty-five of them were successfully identified by matrix assisted laser desorption/ionization time of flight-mass spectrometry (MALDI TOF/TOF MS/MS). Fifty-six percent of the identified proteins belonged to energy and metabolism whereas 29% were stress and defense related. Taken together, the results allow to assess changes at the proteomic level in the host due to the defense response. Results show an initial defense response, not strong enough to overcome the pathogenesis, which may be similar to other susceptible plant-pathogen interactions; however, cross-talks between various defense pathways, regulatory networks and physiological conditions are other important aspects to be considered.     

Further examination of the effects of nitrosylation on Alternaria alternata mycotoxin mutagenicity in vitro

Previously, Alternaria extract and metabolite mutagenicities+/-nitrosylation were characterized using Ames Salmonella strains TA98 and TA100, which are both reverted at GC sites. To examine other targets for mutation, the metabolites Altertoxin I (ATX I), Altenuene (ALT), Alternariol (AOH), Alternariol monomethyl ether (AME), Tentoxin (TENT), Tenuazonic acid (TA) and Radicinin (RAD) were reexamined+/-nitrosylation, using Ames Salmonella strain TA97, sensitive to frameshift mutations at a run of C's, as well as strains TA102 and TA104, reverted by base pair mutations at AT sites and more sensitive to oxidative damage. ATX I was also assessed for mammalian mutagenicity at the Hprt gene locus in Chinese hamster V79 lung fibroblasts and rat hepatoma H4IIE cells. When tested from 1 to 100 microg/plate without nitrosylation, ATX I was mutagenic in TA102+/-rat liver S9 for activation and weakly mutagenic in TA104+/-S9, demonstrating direct-acting AT base pair mutagenicity. AOH was also directly mutagenic at AT sites in TA102+/-S9 while AME was weakly mutagenic in TA102+/-S9 and TA104+S9. Nitrosylation of ATX I enhanced mutagenicity at AT sites in TA104+/-S9 but produced little change in TA102+/-S9 compared to native ATX I. However, nitrosylated ATX I generated a potent direct-acting frameshift mutagen at C sites in TA97+/-S9. While ATX I was not mutagenic in either V79 cells or H4IIE cells, 5 and 10 microg/ml nitrosylated ATX I produced a doubling of 6-thioguanine resistant V79 colonies and 0.5 and 1 microg/ml were mutagenic to H4IIE cells, becoming toxic at higher concentrations. These results suggest ATX I, AME and AOH induce mutations at AT sites, possibly through oxidative damage, with nitrosylation enhancing ATX I frameshift mutagenicity at runs of C's. Nitrosylated ATX I was also directly mutagenic in mammalian test systems.