Drought is one of the major constraints on agricultural productivity worldwide and is likely to further increase. Several adaptations and mitigation strategies are required to cope with drought stress. Plant growth promoting rhizobacteria (PGPR) could play a significant role in alleviation of drought stress in plants. These beneficial microorganisms colonize the rhizosphere/endo-rhizosphere of plants and impart drought tolerance by producing exopolysaccharides (EPS), phytohormones, 1-aminocyclopropane- 1-carboxylate (ACC) deaminase, volatile compounds, inducing accumulation of osmolytes, antioxidants, upregulation or down regulation of stress responsive genes and alteration in root morphology in acquisition of drought tolerance. The term Induced Systemic Tolerance (IST) was coined for physical and chemical changes induced by microorganisms in plants which results in enhanced tolerance to drought stresses. In the present review we elaborate on the role of PGPR in helping plants to cope with drought stress. Copyright © 2015 Elsevier GmbH. All rights reserved.

应用微生物肥料改良土壤是提高土壤及化肥养分利用率的重要途径之一,但微生物肥料的效果受作物及生态条件的影响较大,目前适合东北地区玉米生产的微生物肥料应用研究较少。本研究针对我国东北黑土类型及气候特点,从当地玉米根际土中筛选分离出5株具有不同程度的合成生长素(IAA)、溶磷、解钾、产铁载体等多功能的植物根际促生菌MZ1、MZ2、MZ3、MZ4和MZ5;生态适应性研究发现5株菌均有不同程度的耐盐、耐干旱、耐酸碱以及耐农药等特性;16S rRNA基因序列分析鉴定出它们分别属于鞘氨醇单胞菌、肠杆菌、假单胞菌、芽孢杆菌和根瘤菌;玉米田间试验结果显示,在减施50%氮肥的条件下, 与不接种对照相比,接种MZ1、MZ3和MZ5可增产19.9%~25.0%。因此,MZ1、MZ3和MZ5具有发展为适合东北地区土壤和气候环境的玉米微生物肥料的潜力。

旨在筛选出能产生促进植物生长的挥发性有机化合物（volatile organic compounds,VOCs）的潜在植物根际促生菌（plant growth promoting rhizobacteria,PGPR）,考察其VOCs对植物的促生作用及其它促生功能,为研发微生物肥料提供新的思路及可靠的材料。以本实验室从海洋样品中分离保存的48株功能菌为供试菌株,通过二分隔平板实验、VOCs盆栽实验进行筛选,结合菌株的16S rRNA进行鉴定,通过气相色谱-质谱联用的方法（Gas Chromatography-Mass,GC-MS）对菌株所产VOCs成分进行分析。通过平板活性实验对细菌的固氮,溶磷及产IAA进行活性检测。研究结果显示：筛选得到1株潜在PGPR - GX14001,其所产生的VOCs对本氏烟草（Nicotiana benthamiana）和上海青（Brassica chinensis L.）均表现出明显的促生作用,菌株经16S rRNA鉴定为橙色微杆菌（Microbacterium aurantiacum）。经GC-MS对其VOCs成分分析,共得到7种特异性化合物。经平板活性检测,GX14001具有较强的溶有机/无机磷活性和一般固氮活性,而其产IAA能力较弱,为1.737 μg/mL。PGPR可通过不同的促生机制对植物表现出促生作用,研究结果表明GX14001所产VOCs对植物有明显促生作用,其他方面的促生活性并不高,两者之间不存在较高的正相关性,说明其最主要的促生作用是通过所产生的VOCs获得的。

为了更好地利用分离自棉花根部的内生拮抗细菌S258进行生物防治，特别是利用其产生的挥发性有机物进行植物病害的防治，以棉花黄萎菌和西瓜枯萎菌作为靶标病原真菌，以拟南芥作为指示植物，通过二分格培养皿对峙培养法测定其产生的挥发性有机物对病原真菌的抑菌活性，以及对植物的促生长活性。结果表明，内生细菌S258产生的挥发性有机物对病原真菌的生长具有抑制作用，并且能够促进植物的生长。与阴性对照大肠杆菌DH5α相比，对棉花黄萎菌和西瓜枯萎菌菌丝生长的抑制率分别达到80.9%，10.1%。与不加细菌的空白对照相比，对拟南芥的生长具有很强的促进作用，使拟南芥单株鲜质量达到空白对照的5.3倍。用顶空固相微萃取法收集内生细菌S258产生的挥发性有机物，再用气质联用的方法，分析其挥发性有机物的组成，经NIST和WILIY质谱数据库自动检索，鉴定得到其挥发性有机物包含30种单体化合物，分别属于烷烃、烯烃、醇、酮、醚、醛、酯及杂环类。根据总离子流图的峰面积判断，主要气体成分为二甲基二硫醚和吲哚。综上所述，内生细菌S258能够产生具有抑菌促生长活性的挥发性有机物，是开发为生防产品的重要微生物资源，其挥发性有机物也具有较高的研究和应用价值。

该文对文冠果(Xanthoceras sorbifolia)根系内生菌的种类和固氮活性进行了首次报道。试验以田间栽培的文冠果一、二年生植株为材料, 以Ashby和YMA为培养基, 对根系内生菌进行了分离, 通过对菌落形态的观察, 划线挑取单菌落培养,并对7个代表性的单菌落进行扩大培养, 提取其DNA, 采用细菌16S rDNA通用引物序列进行PCR扩增, 胶回收、测序后, 进行Blast比对分析。试验结果表明: YMA培养基上的菌落数量和种类均明显多于Ashby培养基上的菌落。田间一年生文冠果与田间二年生文冠果的根系内生菌情况存在差异。一年生文冠果的根系内生菌数量与种类略多于二年生文冠果。一年生文冠果根系中分离得到的主要内生菌为成团泛菌(Pantoea agglomerans)、根癌土壤杆菌(Agrobacterium tumefaciens)和产酸克雷伯菌(Klebsiella oxytoca)等; 田间二年生文冠果根系中分离得到的主要内生菌为假单胞菌属(Pseudomonas)细菌。固氮活性测定结果表明, 在所分离的7个菌株中, 6个测到了固氮酶活性, 其中鉴定为产酸克雷伯菌的菌株固氮酶活性显著高于其他菌株,达到9.688 nmol·mg–1·h–1, 为文冠果固氮菌肥的菌种的筛选奠定了基础。

We examined the sensitivity and the specificity of three versions of the Salkowski colorimetric technique. Two of these allowed the detection of indoleacetic acid (IAA) over a low range of concentrations (0.5 to 20 (mu)g/ml), while the third permitted the detection of IAA over a range of higher concentrations (5 to 200 (mu)g/ml). Overall, the three formulations reacted not only with auxin (IAA) but also with indolepyruvic acid and indoleacetamide. Therefore, these techniques appear to be specific for IAA, indolepyruvic acid, and indoleacetamide rather than for IAA alone.

Volatile organic compounds (VOCs) play important roles in the regulation of plant growth and pathogen resistance. However, little is known about the influence of VOCs released from endophytic strains (Burkholderia pyrrocinia strain JK-SH007) on controlling pathogens or inducing systemic resistance in poplar. In this study, we found that VOCs produced by strain JK-SH007 inhibit three poplar canker pathogens (Cytospora chrysosperma, Phomopsis macrospora, and Fusicoccum aesculi) and promote defense enzyme activity and malondialdehyde (MDA) and total phenol (TP) accumulation. Thirteen kinds of VOC components were identified using the solid-phase microextraction combined with gas chromatography-mass spectrometry method. Dimethyl disulfide (DMDS) accounted for the largest proportion of these VOCs. Treatments of poplar seedlings with different volumes of VOC standards (DMDS, benzothiazole, dimethylthiomethane, and phenylacetone) showed that DMDS had the greatest effects on various defense enzyme activities and MDA and TP accumulation. We also found that the inhibitory effect of the VOCs on the three pathogens was gradually enhanced with increasing standard volume. Moreover, the treatment of samples with DMDS significantly reduced the severity and development of the disease caused by three poplar canker pathogens. Comparative transcriptomics analysis of poplar seedlings treated with DMDS showed that there were 1,586 differentially expressed genes in the leaves and stems, and quantitative PCR showed that the gene expression trends were highly consistent with the transcriptome sequencing results. The most significant transcriptomic changes induced by VOCs were related to hormone signal transduction, transcriptional regulation of plant–pathogen interactions, and energy metabolism. Moreover, 137 transcription factors, including members of the ethylene response factor, NAC, WRKY, G2-like, and basic helix-loop-helix protein families, were identified to be involved in the VOC-induced process. This study elucidates the resistance induced by Burkholderia pyrrocinia strain JK-SH007 to poplar canker at the molecular level and can make possible a new method for the comprehensive prevention and control of poplar disease.

Microorganisms have the ability to adapt to a wide range of NaCl concentrations. In general the NaCl tolerance shown by microbes far exceeds the salt tolerance of any other organism, procryote or eukaryote. There are at least three mechanisms available for adaptation to different salt concentrations. The first would be a passive one in which the cytoplasmic ion content would always equal that in the medium. A second mechanism which is used by many organisms involves concentrating compatible solutes to create an osmotic balance between the cytoplasm and the external environment. The third mechanism involves changing the cell physiology to control the movement of water allowing the cell to exist with an ionically dilute cytoplasm. This article will review the major developments and discuss the implications of increasing knowledge about salt tolerance in microorganisms.

Plant growth-promoting rhizobacteria (PGPR) can potentially be used as an alternative strategy to control plant diseases. In this study, strain ST–TJ4 isolated from the rhizosphere soil of a healthy poplar was found to have a strong antifungal activity against 11 phytopathogenic fungi in agriculture and forestry. Strain ST–TJ4 was identified as Pseudomonas sp. based on 16S rRNA-encoding gene sequences. The bacterium can produce siderophores, cellulase, and protease, and has genes involved in the synthesis of phenazine, 1–phenazinecarboxylic acid, pyrrolnitrin, and hydrogen cyanide. Additionally, the volatile compounds released by strain ST–TJ4 can inhibit the mycelial growth of plant pathogenic fungi more than diffusible substances can. Based on volatile compound profiles of strain ST–TJ4 obtained from headspace collection and GC–MS/MS analysis, 1-undecene was identified. In summary, the results suggested that Pseudomonas sp. ST–TJ4 can be used as a biocontrol agent for various plant diseases caused by phytopathogenic fungi.

\n Bacillus amyloliquefaciens\n NJN-6 produces volatile compounds (VOCs) that inhibit the growth and spore germination of\n Fusarium oxysporum\n f. sp.\n cubense\n. Among the total of 36 volatile compounds detected, 11 compounds completely inhibited fungal growth. The antifungal activity of these compounds suggested that VOCs can play important roles over short and long distances in the suppression of\n Fusarium oxysporum\n.\n

黄瓜幼苗经水杨酸处理后，POD、PPO、PAL3种酶活性均有不同程度的变化，与对照相比，POD活性在处理后24h有明显提高，以后一直呈上升趋势，至144h后较对提高1930%。PPO活性变化相对较小，酶活性的明显提高在处理48h以后，处理后144h时较对照提高617%。PAL在处理后72h时出现一个小的酶活性峰，较对照提高176%，而后下降，120h出现第2个活性峰，较对照提高308%。处理后4d接种霜霉病菌，调查结果表明：第1真叶处理较对照病情指数降低89%，第2真叶处理较对照降低221%。